database/postgres
database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-04-25 21:42:33 +03:00
Code
postgres/src/backend/optimizer/plan/planner.c
Tom Lane 5864d6a4b6 Provide a planner hook at a suitable place for creating upper-rel Paths. 
In the initial revision of the upper-planner pathification work, the only
available way for an FDW or custom-scan provider to inject Paths
representing post-scan-join processing was to insert them during scan-level
GetForeignPaths or similar processing.  While that's not impossible, it'd
require quite a lot of duplicative processing to look forward and see if
the extension would be capable of implementing the whole query.  To improve
matters for custom-scan providers, provide a hook function at the point
where the core code is about to start filling in upperrel Paths.  At this
point Paths are available for the whole scan/join tree, which should reduce
the amount of redundant effort considerably.

(An alternative design that was suggested was to provide a separate hook
for each post-scan-join processing step, but that seems messy and not
clearly more useful.)

Following our time-honored tradition, there's no documentation for this
hook outside the source code.

As-is, this hook is only meant for custom scan providers, which we can't
assume very much about.  A followon patch will implement an FDW callback
to let FDWs do the same thing in a somewhat more structured fashion.
2016-03-14 19:23:29 -04:00

4590 lines
143 KiB
C
Raw Blame History

/*-------------------------------------------------------------------------
*
* planner.c
* The query optimizer external interface.
*
* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/plan/planner.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <limits.h>
#include <math.h>
#include "access/htup_details.h"
#include "access/parallel.h"
#include "access/sysattr.h"
#include "access/xact.h"
#include "catalog/pg_constraint_fn.h"
#include "executor/executor.h"
#include "executor/nodeAgg.h"
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "lib/bipartite_match.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#ifdef OPTIMIZER_DEBUG
#include "nodes/print.h"
#endif
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/plancat.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/subselect.h"
#include "optimizer/tlist.h"
#include "optimizer/var.h"
#include "parser/analyze.h"
#include "parser/parsetree.h"
#include "parser/parse_agg.h"
#include "rewrite/rewriteManip.h"
#include "storage/dsm_impl.h"
#include "utils/rel.h"
#include "utils/selfuncs.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
/* GUC parameters */
double cursor_tuple_fraction = DEFAULT_CURSOR_TUPLE_FRACTION;
int force_parallel_mode = FORCE_PARALLEL_OFF;
/* Hook for plugins to get control in planner() */
planner_hook_type planner_hook = NULL;
/* Hook for plugins to get control before grouping_planner plans upper rels */
create_upper_paths_hook_type create_upper_paths_hook = NULL;
/* Expression kind codes for preprocess_expression */
#define EXPRKIND_QUAL 0
#define EXPRKIND_TARGET 1
#define EXPRKIND_RTFUNC 2
#define EXPRKIND_RTFUNC_LATERAL 3
#define EXPRKIND_VALUES 4
#define EXPRKIND_VALUES_LATERAL 5
#define EXPRKIND_LIMIT 6
#define EXPRKIND_APPINFO 7
#define EXPRKIND_PHV 8
#define EXPRKIND_TABLESAMPLE 9
/* Passthrough data for standard_qp_callback */
typedef struct
{
List *tlist; /* preprocessed query targetlist */
List *activeWindows; /* active windows, if any */
List *groupClause; /* overrides parse->groupClause */
} standard_qp_extra;
/* Local functions */
static Node *preprocess_expression(PlannerInfo *root, Node *expr, int kind);
static void preprocess_qual_conditions(PlannerInfo *root, Node *jtnode);
static void inheritance_planner(PlannerInfo *root);
static void grouping_planner(PlannerInfo *root, bool inheritance_update,
double tuple_fraction);
static void preprocess_rowmarks(PlannerInfo *root);
static double preprocess_limit(PlannerInfo *root,
double tuple_fraction,
int64 *offset_est, int64 *count_est);
static bool limit_needed(Query *parse);
static void remove_useless_groupby_columns(PlannerInfo *root);
static List *preprocess_groupclause(PlannerInfo *root, List *force);
static List *extract_rollup_sets(List *groupingSets);
static List *reorder_grouping_sets(List *groupingSets, List *sortclause);
static void standard_qp_callback(PlannerInfo *root, void *extra);
static double get_number_of_groups(PlannerInfo *root,
double path_rows,
List *rollup_lists,
List *rollup_groupclauses);
static RelOptInfo *create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
List *rollup_lists,
List *rollup_groupclauses);
static RelOptInfo *create_window_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *input_target,
PathTarget *output_target,
List *tlist,
WindowFuncLists *wflists,
List *activeWindows);
static void create_one_window_path(PlannerInfo *root,
RelOptInfo *window_rel,
Path *path,
PathTarget *input_target,
PathTarget *output_target,
List *tlist,
WindowFuncLists *wflists,
List *activeWindows);
static RelOptInfo *create_distinct_paths(PlannerInfo *root,
RelOptInfo *input_rel);
static RelOptInfo *create_ordered_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
double limit_tuples);
static PathTarget *make_group_input_target(PlannerInfo *root,
PathTarget *final_target);
static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
static List *select_active_windows(PlannerInfo *root, WindowFuncLists *wflists);
static PathTarget *make_window_input_target(PlannerInfo *root,
PathTarget *final_target,
List *activeWindows);
static List *make_pathkeys_for_window(PlannerInfo *root, WindowClause *wc,
List *tlist);
static PathTarget *make_sort_input_target(PlannerInfo *root,
PathTarget *final_target,
bool *have_postponed_srfs);
/*****************************************************************************
*
* Query optimizer entry point
*
* To support loadable plugins that monitor or modify planner behavior,
* we provide a hook variable that lets a plugin get control before and
* after the standard planning process. The plugin would normally call
* standard_planner().
*
* Note to plugin authors: standard_planner() scribbles on its Query input,
* so you'd better copy that data structure if you want to plan more than once.
*
*****************************************************************************/
PlannedStmt *
planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
{
PlannedStmt *result;
if (planner_hook)
result = (*planner_hook) (parse, cursorOptions, boundParams);
else
result = standard_planner(parse, cursorOptions, boundParams);
return result;
}
PlannedStmt *
standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
{
PlannedStmt *result;
PlannerGlobal *glob;
double tuple_fraction;
PlannerInfo *root;
RelOptInfo *final_rel;
Path *best_path;
Plan *top_plan;
ListCell *lp,
*lr;
/* Cursor options may come from caller or from DECLARE CURSOR stmt */
if (parse->utilityStmt &&
IsA(parse->utilityStmt, DeclareCursorStmt))
cursorOptions |= ((DeclareCursorStmt *) parse->utilityStmt)->options;
/*
* Set up global state for this planner invocation. This data is needed
* across all levels of sub-Query that might exist in the given command,
* so we keep it in a separate struct that's linked to by each per-Query
* PlannerInfo.
*/
glob = makeNode(PlannerGlobal);
glob->boundParams = boundParams;
glob->subplans = NIL;
glob->subroots = NIL;
glob->rewindPlanIDs = NULL;
glob->finalrtable = NIL;
glob->finalrowmarks = NIL;
glob->resultRelations = NIL;
glob->relationOids = NIL;
glob->invalItems = NIL;
glob->nParamExec = 0;
glob->lastPHId = 0;
glob->lastRowMarkId = 0;
glob->lastPlanNodeId = 0;
glob->transientPlan = false;
glob->hasRowSecurity = false;
glob->hasForeignJoin = false;
/*
* Assess whether it's feasible to use parallel mode for this query. We
* can't do this in a standalone backend, or if the command will try to
* modify any data, or if this is a cursor operation, or if GUCs are set
* to values that don't permit parallelism, or if parallel-unsafe
* functions are present in the query tree.
*
* For now, we don't try to use parallel mode if we're running inside a
* parallel worker. We might eventually be able to relax this
* restriction, but for now it seems best not to have parallel workers
* trying to create their own parallel workers.
*
* We can't use parallelism in serializable mode because the predicate
* locking code is not parallel-aware. It's not catastrophic if someone
* tries to run a parallel plan in serializable mode; it just won't get
* any workers and will run serially. But it seems like a good heuristic
* to assume that the same serialization level will be in effect at plan
* time and execution time, so don't generate a parallel plan if we're in
* serializable mode.
*/
glob->parallelModeOK = (cursorOptions & CURSOR_OPT_PARALLEL_OK) != 0 &&
IsUnderPostmaster && dynamic_shared_memory_type != DSM_IMPL_NONE &&
parse->commandType == CMD_SELECT && !parse->hasModifyingCTE &&
parse->utilityStmt == NULL && max_parallel_degree > 0 &&
!IsParallelWorker() && !IsolationIsSerializable() &&
!has_parallel_hazard((Node *) parse, true);
/*
* glob->parallelModeNeeded should tell us whether it's necessary to
* impose the parallel mode restrictions, but we don't actually want to
* impose them unless we choose a parallel plan, so that people who
* mislabel their functions but don't use parallelism anyway aren't
* harmed. But when force_parallel_mode is set, we enable the restrictions
* whenever possible for testing purposes.
*
* glob->wholePlanParallelSafe should tell us whether it's OK to stick a
* Gather node on top of the entire plan. However, it only needs to be
* accurate when force_parallel_mode is 'on' or 'regress', so we don't
* bother doing the work otherwise. The value we set here is just a
* preliminary guess; it may get changed from true to false later, but not
* vice versa.
*/
if (force_parallel_mode == FORCE_PARALLEL_OFF || !glob->parallelModeOK)
{
glob->parallelModeNeeded = false;
glob->wholePlanParallelSafe = false; /* either false or don't care */
}
else
{
glob->parallelModeNeeded = true;
glob->wholePlanParallelSafe =
!has_parallel_hazard((Node *) parse, false);
}
/* Determine what fraction of the plan is likely to be scanned */
if (cursorOptions & CURSOR_OPT_FAST_PLAN)
{
/*
* We have no real idea how many tuples the user will ultimately FETCH
* from a cursor, but it is often the case that he doesn't want 'em
* all, or would prefer a fast-start plan anyway so that he can
* process some of the tuples sooner. Use a GUC parameter to decide
* what fraction to optimize for.
*/
tuple_fraction = cursor_tuple_fraction;
/*
* We document cursor_tuple_fraction as simply being a fraction, which
* means the edge cases 0 and 1 have to be treated specially here. We
* convert 1 to 0 ("all the tuples") and 0 to a very small fraction.
*/
if (tuple_fraction >= 1.0)
tuple_fraction = 0.0;
else if (tuple_fraction <= 0.0)
tuple_fraction = 1e-10;
}
else
{
/* Default assumption is we need all the tuples */
tuple_fraction = 0.0;
}
/* primary planning entry point (may recurse for subqueries) */
root = subquery_planner(glob, parse, NULL,
false, tuple_fraction);
/* Select best Path and turn it into a Plan */
final_rel = fetch_upper_rel(root, UPPERREL_FINAL, NULL);
best_path = get_cheapest_fractional_path(final_rel, tuple_fraction);
top_plan = create_plan(root, best_path);
/*
* If creating a plan for a scrollable cursor, make sure it can run
* backwards on demand. Add a Material node at the top at need.
*/
if (cursorOptions & CURSOR_OPT_SCROLL)
{
if (!ExecSupportsBackwardScan(top_plan))
top_plan = materialize_finished_plan(top_plan);
}
/*
* At present, we don't copy subplans to workers. The presence of a
* subplan in one part of the plan doesn't preclude the use of parallelism
* in some other part of the plan, but it does preclude the possibility of
* regarding the entire plan parallel-safe.
*/
if (glob->subplans != NULL)
glob->wholePlanParallelSafe = false;
/*
* Optionally add a Gather node for testing purposes, provided this is
* actually a safe thing to do.
*/
if (glob->wholePlanParallelSafe &&
force_parallel_mode != FORCE_PARALLEL_OFF)
{
Gather *gather = makeNode(Gather);
gather->plan.targetlist = top_plan->targetlist;
gather->plan.qual = NIL;
gather->plan.lefttree = top_plan;
gather->plan.righttree = NULL;
gather->num_workers = 1;
gather->single_copy = true;
gather->invisible = (force_parallel_mode == FORCE_PARALLEL_REGRESS);
root->glob->parallelModeNeeded = true;
top_plan = &gather->plan;
}
/*
* If any Params were generated, run through the plan tree and compute
* each plan node's extParam/allParam sets. Ideally we'd merge this into
* set_plan_references' tree traversal, but for now it has to be separate
* because we need to visit subplans before not after main plan.
*/
if (glob->nParamExec > 0)
{
Assert(list_length(glob->subplans) == list_length(glob->subroots));
forboth(lp, glob->subplans, lr, glob->subroots)
{
Plan *subplan = (Plan *) lfirst(lp);
PlannerInfo *subroot = (PlannerInfo *) lfirst(lr);
SS_finalize_plan(subroot, subplan);
}
SS_finalize_plan(root, top_plan);
}
/* final cleanup of the plan */
Assert(glob->finalrtable == NIL);
Assert(glob->finalrowmarks == NIL);
Assert(glob->resultRelations == NIL);
top_plan = set_plan_references(root, top_plan);
/* ... and the subplans (both regular subplans and initplans) */
Assert(list_length(glob->subplans) == list_length(glob->subroots));
forboth(lp, glob->subplans, lr, glob->subroots)
{
Plan *subplan = (Plan *) lfirst(lp);
PlannerInfo *subroot = (PlannerInfo *) lfirst(lr);
lfirst(lp) = set_plan_references(subroot, subplan);
}
/* build the PlannedStmt result */
result = makeNode(PlannedStmt);
result->commandType = parse->commandType;
result->queryId = parse->queryId;
result->hasReturning = (parse->returningList != NIL);
result->hasModifyingCTE = parse->hasModifyingCTE;
result->canSetTag = parse->canSetTag;
result->transientPlan = glob->transientPlan;
result->planTree = top_plan;
result->rtable = glob->finalrtable;
result->resultRelations = glob->resultRelations;
result->utilityStmt = parse->utilityStmt;
result->subplans = glob->subplans;
result->rewindPlanIDs = glob->rewindPlanIDs;
result->rowMarks = glob->finalrowmarks;
result->relationOids = glob->relationOids;
result->invalItems = glob->invalItems;
result->nParamExec = glob->nParamExec;
result->hasRowSecurity = glob->hasRowSecurity;
result->parallelModeNeeded = glob->parallelModeNeeded;
result->hasForeignJoin = glob->hasForeignJoin;
return result;
}
/*--------------------
* subquery_planner
* Invokes the planner on a subquery. We recurse to here for each
* sub-SELECT found in the query tree.
*
* glob is the global state for the current planner run.
* parse is the querytree produced by the parser & rewriter.
* parent_root is the immediate parent Query's info (NULL at the top level).
* hasRecursion is true if this is a recursive WITH query.
* tuple_fraction is the fraction of tuples we expect will be retrieved.
* tuple_fraction is interpreted as explained for grouping_planner, below.
*
* Basically, this routine does the stuff that should only be done once
* per Query object. It then calls grouping_planner. At one time,
* grouping_planner could be invoked recursively on the same Query object;
* that's not currently true, but we keep the separation between the two
* routines anyway, in case we need it again someday.
*
* subquery_planner will be called recursively to handle sub-Query nodes
* found within the query's expressions and rangetable.
*
* Returns the PlannerInfo struct ("root") that contains all data generated
* while planning the subquery. In particular, the Path(s) attached to
* the (UPPERREL_FINAL, NULL) upperrel represent our conclusions about the
* cheapest way(s) to implement the query. The top level will select the
* best Path and pass it through createplan.c to produce a finished Plan.
*--------------------
*/
PlannerInfo *
subquery_planner(PlannerGlobal *glob, Query *parse,
PlannerInfo *parent_root,
bool hasRecursion, double tuple_fraction)
{
PlannerInfo *root;
List *newWithCheckOptions;
List *newHaving;
bool hasOuterJoins;
RelOptInfo *final_rel;
ListCell *l;
/* Create a PlannerInfo data structure for this subquery */
root = makeNode(PlannerInfo);
root->parse = parse;
root->glob = glob;
root->query_level = parent_root ? parent_root->query_level + 1 : 1;
root->parent_root = parent_root;
root->plan_params = NIL;
root->outer_params = NULL;
root->planner_cxt = CurrentMemoryContext;
root->init_plans = NIL;
root->cte_plan_ids = NIL;
root->multiexpr_params = NIL;
root->eq_classes = NIL;
root->append_rel_list = NIL;
root->rowMarks = NIL;
memset(root->upper_rels, 0, sizeof(root->upper_rels));
memset(root->upper_targets, 0, sizeof(root->upper_targets));
root->processed_tlist = NIL;
root->grouping_map = NULL;
root->minmax_aggs = NIL;
root->hasInheritedTarget = false;
root->hasRecursion = hasRecursion;
if (hasRecursion)
root->wt_param_id = SS_assign_special_param(root);
else
root->wt_param_id = -1;
root->non_recursive_path = NULL;
/*
* If there is a WITH list, process each WITH query and build an initplan
* SubPlan structure for it.
*/
if (parse->cteList)
SS_process_ctes(root);
/*
* Look for ANY and EXISTS SubLinks in WHERE and JOIN/ON clauses, and try
* to transform them into joins. Note that this step does not descend
* into subqueries; if we pull up any subqueries below, their SubLinks are
* processed just before pulling them up.
*/
if (parse->hasSubLinks)
pull_up_sublinks(root);
/*
* Scan the rangetable for set-returning functions, and inline them if
* possible (producing subqueries that might get pulled up next).
* Recursion issues here are handled in the same way as for SubLinks.
*/
inline_set_returning_functions(root);
/*
* Check to see if any subqueries in the jointree can be merged into this
* query.
*/
pull_up_subqueries(root);
/*
* If this is a simple UNION ALL query, flatten it into an appendrel. We
* do this now because it requires applying pull_up_subqueries to the leaf
* queries of the UNION ALL, which weren't touched above because they
* weren't referenced by the jointree (they will be after we do this).
*/
if (parse->setOperations)
flatten_simple_union_all(root);
/*
* Detect whether any rangetable entries are RTE_JOIN kind; if not, we can
* avoid the expense of doing flatten_join_alias_vars(). Also check for
* outer joins --- if none, we can skip reduce_outer_joins(). And check
* for LATERAL RTEs, too. This must be done after we have done
* pull_up_subqueries(), of course.
*/
root->hasJoinRTEs = false;
root->hasLateralRTEs = false;
hasOuterJoins = false;
foreach(l, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
if (rte->rtekind == RTE_JOIN)
{
root->hasJoinRTEs = true;
if (IS_OUTER_JOIN(rte->jointype))
hasOuterJoins = true;
}
if (rte->lateral)
root->hasLateralRTEs = true;
}
/*
* Preprocess RowMark information. We need to do this after subquery
* pullup (so that all non-inherited RTEs are present) and before
* inheritance expansion (so that the info is available for
* expand_inherited_tables to examine and modify).
*/
preprocess_rowmarks(root);
/*
* Expand any rangetable entries that are inheritance sets into "append
* relations". This can add entries to the rangetable, but they must be
* plain base relations not joins, so it's OK (and marginally more
* efficient) to do it after checking for join RTEs. We must do it after
* pulling up subqueries, else we'd fail to handle inherited tables in
* subqueries.
*/
expand_inherited_tables(root);
/*
* Set hasHavingQual to remember if HAVING clause is present. Needed
* because preprocess_expression will reduce a constant-true condition to
* an empty qual list ... but "HAVING TRUE" is not a semantic no-op.
*/
root->hasHavingQual = (parse->havingQual != NULL);
/* Clear this flag; might get set in distribute_qual_to_rels */
root->hasPseudoConstantQuals = false;
/*
* Do expression preprocessing on targetlist and quals, as well as other
* random expressions in the querytree. Note that we do not need to
* handle sort/group expressions explicitly, because they are actually
* part of the targetlist.
*/
parse->targetList = (List *)
preprocess_expression(root, (Node *) parse->targetList,
EXPRKIND_TARGET);
newWithCheckOptions = NIL;
foreach(l, parse->withCheckOptions)
{
WithCheckOption *wco = (WithCheckOption *) lfirst(l);
wco->qual = preprocess_expression(root, wco->qual,
EXPRKIND_QUAL);
if (wco->qual != NULL)
newWithCheckOptions = lappend(newWithCheckOptions, wco);
}
parse->withCheckOptions = newWithCheckOptions;
parse->returningList = (List *)
preprocess_expression(root, (Node *) parse->returningList,
EXPRKIND_TARGET);
preprocess_qual_conditions(root, (Node *) parse->jointree);
parse->havingQual = preprocess_expression(root, parse->havingQual,
EXPRKIND_QUAL);
foreach(l, parse->windowClause)
{
WindowClause *wc = (WindowClause *) lfirst(l);
/* partitionClause/orderClause are sort/group expressions */
wc->startOffset = preprocess_expression(root, wc->startOffset,
EXPRKIND_LIMIT);
wc->endOffset = preprocess_expression(root, wc->endOffset,
EXPRKIND_LIMIT);
}
parse->limitOffset = preprocess_expression(root, parse->limitOffset,
EXPRKIND_LIMIT);
parse->limitCount = preprocess_expression(root, parse->limitCount,
EXPRKIND_LIMIT);
if (parse->onConflict)
{
parse->onConflict->onConflictSet = (List *)
preprocess_expression(root, (Node *) parse->onConflict->onConflictSet,
EXPRKIND_TARGET);
parse->onConflict->onConflictWhere =
preprocess_expression(root, (Node *) parse->onConflict->onConflictWhere,
EXPRKIND_QUAL);
}
root->append_rel_list = (List *)
preprocess_expression(root, (Node *) root->append_rel_list,
EXPRKIND_APPINFO);
/* Also need to preprocess expressions within RTEs */
foreach(l, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
int kind;
if (rte->rtekind == RTE_RELATION)
{
if (rte->tablesample)
rte->tablesample = (TableSampleClause *)
preprocess_expression(root,
(Node *) rte->tablesample,
EXPRKIND_TABLESAMPLE);
}
else if (rte->rtekind == RTE_SUBQUERY)
{
/*
* We don't want to do all preprocessing yet on the subquery's
* expressions, since that will happen when we plan it. But if it
* contains any join aliases of our level, those have to get
* expanded now, because planning of the subquery won't do it.
* That's only possible if the subquery is LATERAL.
*/
if (rte->lateral && root->hasJoinRTEs)
rte->subquery = (Query *)
flatten_join_alias_vars(root, (Node *) rte->subquery);
}
else if (rte->rtekind == RTE_FUNCTION)
{
/* Preprocess the function expression(s) fully */
kind = rte->lateral ? EXPRKIND_RTFUNC_LATERAL : EXPRKIND_RTFUNC;
rte->functions = (List *) preprocess_expression(root, (Node *) rte->functions, kind);
}
else if (rte->rtekind == RTE_VALUES)
{
/* Preprocess the values lists fully */
kind = rte->lateral ? EXPRKIND_VALUES_LATERAL : EXPRKIND_VALUES;
rte->values_lists = (List *)
preprocess_expression(root, (Node *) rte->values_lists, kind);
}
}
/*
* In some cases we may want to transfer a HAVING clause into WHERE. We
* cannot do so if the HAVING clause contains aggregates (obviously) or
* volatile functions (since a HAVING clause is supposed to be executed
* only once per group). We also can't do this if there are any nonempty
* grouping sets; moving such a clause into WHERE would potentially change
* the results, if any referenced column isn't present in all the grouping
* sets. (If there are only empty grouping sets, then the HAVING clause
* must be degenerate as discussed below.)
*
* Also, it may be that the clause is so expensive to execute that we're
* better off doing it only once per group, despite the loss of
* selectivity. This is hard to estimate short of doing the entire
* planning process twice, so we use a heuristic: clauses containing
* subplans are left in HAVING. Otherwise, we move or copy the HAVING
* clause into WHERE, in hopes of eliminating tuples before aggregation
* instead of after.
*
* If the query has explicit grouping then we can simply move such a
* clause into WHERE; any group that fails the clause will not be in the
* output because none of its tuples will reach the grouping or
* aggregation stage. Otherwise we must have a degenerate (variable-free)
* HAVING clause, which we put in WHERE so that query_planner() can use it
* in a gating Result node, but also keep in HAVING to ensure that we
* don't emit a bogus aggregated row. (This could be done better, but it
* seems not worth optimizing.)
*
* Note that both havingQual and parse->jointree->quals are in
* implicitly-ANDed-list form at this point, even though they are declared
* as Node *.
*/
newHaving = NIL;
foreach(l, (List *) parse->havingQual)
{
Node *havingclause = (Node *) lfirst(l);
if ((parse->groupClause && parse->groupingSets) ||
contain_agg_clause(havingclause) ||
contain_volatile_functions(havingclause) ||
contain_subplans(havingclause))
{
/* keep it in HAVING */
newHaving = lappend(newHaving, havingclause);
}
else if (parse->groupClause && !parse->groupingSets)
{
/* move it to WHERE */
parse->jointree->quals = (Node *)
lappend((List *) parse->jointree->quals, havingclause);
}
else
{
/* put a copy in WHERE, keep it in HAVING */
parse->jointree->quals = (Node *)
lappend((List *) parse->jointree->quals,
copyObject(havingclause));
newHaving = lappend(newHaving, havingclause);
}
}
parse->havingQual = (Node *) newHaving;
/* Remove any redundant GROUP BY columns */
remove_useless_groupby_columns(root);
/*
* If we have any outer joins, try to reduce them to plain inner joins.
* This step is most easily done after we've done expression
* preprocessing.
*/
if (hasOuterJoins)
reduce_outer_joins(root);
/*
* Do the main planning. If we have an inherited target relation, that
* needs special processing, else go straight to grouping_planner.
*/
if (parse->resultRelation &&
rt_fetch(parse->resultRelation, parse->rtable)->inh)
inheritance_planner(root);
else
grouping_planner(root, false, tuple_fraction);
/*
* Capture the set of outer-level param IDs we have access to, for use in
* extParam/allParam calculations later.
*/
SS_identify_outer_params(root);
/*
* If any initPlans were created in this query level, increment the
* surviving Paths' costs to account for them. They won't actually get
* attached to the plan tree till create_plan() runs, but we want to be
* sure their costs are included now.
*/
final_rel = fetch_upper_rel(root, UPPERREL_FINAL, NULL);
SS_charge_for_initplans(root, final_rel);
/*
* Make sure we've identified the cheapest Path for the final rel. (By
* doing this here not in grouping_planner, we include initPlan costs in
* the decision, though it's unlikely that will change anything.)
*/
set_cheapest(final_rel);
return root;
}
/*
* preprocess_expression
* Do subquery_planner's preprocessing work for an expression,
* which can be a targetlist, a WHERE clause (including JOIN/ON
* conditions), a HAVING clause, or a few other things.
*/
static Node *
preprocess_expression(PlannerInfo *root, Node *expr, int kind)
{
/*
* Fall out quickly if expression is empty. This occurs often enough to
* be worth checking. Note that null->null is the correct conversion for
* implicit-AND result format, too.
*/
if (expr == NULL)
return NULL;
/*
* If the query has any join RTEs, replace join alias variables with
* base-relation variables. We must do this before sublink processing,
* else sublinks expanded out from join aliases would not get processed.
* We can skip it in non-lateral RTE functions, VALUES lists, and
* TABLESAMPLE clauses, however, since they can't contain any Vars of the
* current query level.
*/
if (root->hasJoinRTEs &&
!(kind == EXPRKIND_RTFUNC ||
kind == EXPRKIND_VALUES ||
kind == EXPRKIND_TABLESAMPLE))
expr = flatten_join_alias_vars(root, expr);
/*
* Simplify constant expressions.
*
* Note: an essential effect of this is to convert named-argument function
* calls to positional notation and insert the current actual values of
* any default arguments for functions. To ensure that happens, we *must*
* process all expressions here. Previous PG versions sometimes skipped
* const-simplification if it didn't seem worth the trouble, but we can't
* do that anymore.
*
* Note: this also flattens nested AND and OR expressions into N-argument
* form. All processing of a qual expression after this point must be
* careful to maintain AND/OR flatness --- that is, do not generate a tree
* with AND directly under AND, nor OR directly under OR.
*/
expr = eval_const_expressions(root, expr);
/*
* If it's a qual or havingQual, canonicalize it.
*/
if (kind == EXPRKIND_QUAL)
{
expr = (Node *) canonicalize_qual((Expr *) expr);
#ifdef OPTIMIZER_DEBUG
printf("After canonicalize_qual()\n");
pprint(expr);
#endif
}
/* Expand SubLinks to SubPlans */
if (root->parse->hasSubLinks)
expr = SS_process_sublinks(root, expr, (kind == EXPRKIND_QUAL));
/*
* XXX do not insert anything here unless you have grokked the comments in
* SS_replace_correlation_vars ...
*/
/* Replace uplevel vars with Param nodes (this IS possible in VALUES) */
if (root->query_level > 1)
expr = SS_replace_correlation_vars(root, expr);
/*
* If it's a qual or havingQual, convert it to implicit-AND format. (We
* don't want to do this before eval_const_expressions, since the latter
* would be unable to simplify a top-level AND correctly. Also,
* SS_process_sublinks expects explicit-AND format.)
*/
if (kind == EXPRKIND_QUAL)
expr = (Node *) make_ands_implicit((Expr *) expr);
return expr;
}
/*
* preprocess_qual_conditions
* Recursively scan the query's jointree and do subquery_planner's
* preprocessing work on each qual condition found therein.
*/
static void
preprocess_qual_conditions(PlannerInfo *root, Node *jtnode)
{
if (jtnode == NULL)
return;
if (IsA(jtnode, RangeTblRef))
{
/* nothing to do here */
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
foreach(l, f->fromlist)
preprocess_qual_conditions(root, lfirst(l));
f->quals = preprocess_expression(root, f->quals, EXPRKIND_QUAL);
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
preprocess_qual_conditions(root, j->larg);
preprocess_qual_conditions(root, j->rarg);
j->quals = preprocess_expression(root, j->quals, EXPRKIND_QUAL);
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
}
/*
* preprocess_phv_expression
* Do preprocessing on a PlaceHolderVar expression that's been pulled up.
*
* If a LATERAL subquery references an output of another subquery, and that
* output must be wrapped in a PlaceHolderVar because of an intermediate outer
* join, then we'll push the PlaceHolderVar expression down into the subquery
* and later pull it back up during find_lateral_references, which runs after
* subquery_planner has preprocessed all the expressions that were in the
* current query level to start with. So we need to preprocess it then.
*/
Expr *
preprocess_phv_expression(PlannerInfo *root, Expr *expr)
{
return (Expr *) preprocess_expression(root, (Node *) expr, EXPRKIND_PHV);
}
/*
* inheritance_planner
* Generate Paths in the case where the result relation is an
* inheritance set.
*
* We have to handle this case differently from cases where a source relation
* is an inheritance set. Source inheritance is expanded at the bottom of the
* plan tree (see allpaths.c), but target inheritance has to be expanded at
* the top. The reason is that for UPDATE, each target relation needs a
* different targetlist matching its own column set. Fortunately,
* the UPDATE/DELETE target can never be the nullable side of an outer join,
* so it's OK to generate the plan this way.
*
* Returns nothing; the useful output is in the Paths we attach to
* the (UPPERREL_FINAL, NULL) upperrel stored in *root.
*
* Note that we have not done set_cheapest() on the final rel; it's convenient
* to leave this to the caller.
*/
static void
inheritance_planner(PlannerInfo *root)
{
Query *parse = root->parse;
int parentRTindex = parse->resultRelation;
Bitmapset *resultRTindexes;
Bitmapset *subqueryRTindexes;
Bitmapset *modifiableARIindexes;
int nominalRelation = -1;
List *final_rtable = NIL;
int save_rel_array_size = 0;
RelOptInfo **save_rel_array = NULL;
List *subpaths = NIL;
List *subroots = NIL;
List *resultRelations = NIL;
List *withCheckOptionLists = NIL;
List *returningLists = NIL;
List *rowMarks;
RelOptInfo *final_rel;
ListCell *lc;
Index rti;
Assert(parse->commandType != CMD_INSERT);
/*
* We generate a modified instance of the original Query for each target
* relation, plan that, and put all the plans into a list that will be
* controlled by a single ModifyTable node. All the instances share the
* same rangetable, but each instance must have its own set of subquery
* RTEs within the finished rangetable because (1) they are likely to get
* scribbled on during planning, and (2) it's not inconceivable that
* subqueries could get planned differently in different cases. We need
* not create duplicate copies of other RTE kinds, in particular not the
* target relations, because they don't have either of those issues. Not
* having to duplicate the target relations is important because doing so
* (1) would result in a rangetable of length O(N^2) for N targets, with
* at least O(N^3) work expended here; and (2) would greatly complicate
* management of the rowMarks list.
*
* Note that any RTEs with security barrier quals will be turned into
* subqueries during planning, and so we must create copies of them too,
* except where they are target relations, which will each only be used in
* a single plan.
*
* To begin with, we'll need a bitmapset of the target relation relids.
*/
resultRTindexes = bms_make_singleton(parentRTindex);
foreach(lc, root->append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
if (appinfo->parent_relid == parentRTindex)
resultRTindexes = bms_add_member(resultRTindexes,
appinfo->child_relid);
}
/*
* Now, generate a bitmapset of the relids of the subquery RTEs, including
* security-barrier RTEs that will become subqueries, as just explained.
*/
subqueryRTindexes = NULL;
rti = 1;
foreach(lc, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
if (rte->rtekind == RTE_SUBQUERY ||
(rte->securityQuals != NIL &&
!bms_is_member(rti, resultRTindexes)))
subqueryRTindexes = bms_add_member(subqueryRTindexes, rti);
rti++;
}
/*
* Next, we want to identify which AppendRelInfo items contain references
* to any of the aforesaid subquery RTEs. These items will need to be
* copied and modified to adjust their subquery references; whereas the
* other ones need not be touched. It's worth being tense over this
* because we can usually avoid processing most of the AppendRelInfo
* items, thereby saving O(N^2) space and time when the target is a large
* inheritance tree. We can identify AppendRelInfo items by their
* child_relid, since that should be unique within the list.
*/
modifiableARIindexes = NULL;
if (subqueryRTindexes != NULL)
{
foreach(lc, root->append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
if (bms_is_member(appinfo->parent_relid, subqueryRTindexes) ||
bms_is_member(appinfo->child_relid, subqueryRTindexes) ||
bms_overlap(pull_varnos((Node *) appinfo->translated_vars),
subqueryRTindexes))
modifiableARIindexes = bms_add_member(modifiableARIindexes,
appinfo->child_relid);
}
}
/*
* And now we can get on with generating a plan for each child table.
*/
foreach(lc, root->append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
PlannerInfo *subroot;
RelOptInfo *sub_final_rel;
Path *subpath;
/* append_rel_list contains all append rels; ignore others */
if (appinfo->parent_relid != parentRTindex)
continue;
/*
* We need a working copy of the PlannerInfo so that we can control
* propagation of information back to the main copy.
*/
subroot = makeNode(PlannerInfo);
memcpy(subroot, root, sizeof(PlannerInfo));
/*
* Generate modified query with this rel as target. We first apply
* adjust_appendrel_attrs, which copies the Query and changes
* references to the parent RTE to refer to the current child RTE,
* then fool around with subquery RTEs.
*/
subroot->parse = (Query *)
adjust_appendrel_attrs(root,
(Node *) parse,
appinfo);
/*
* The rowMarks list might contain references to subquery RTEs, so
* make a copy that we can apply ChangeVarNodes to. (Fortunately, the
* executor doesn't need to see the modified copies --- we can just
* pass it the original rowMarks list.)
*/
subroot->rowMarks = (List *) copyObject(root->rowMarks);
/*
* The append_rel_list likewise might contain references to subquery
* RTEs (if any subqueries were flattenable UNION ALLs). So prepare
* to apply ChangeVarNodes to that, too. As explained above, we only
* want to copy items that actually contain such references; the rest
* can just get linked into the subroot's append_rel_list.
*
* If we know there are no such references, we can just use the outer
* append_rel_list unmodified.
*/
if (modifiableARIindexes != NULL)
{
ListCell *lc2;
subroot->append_rel_list = NIL;
foreach(lc2, root->append_rel_list)
{
AppendRelInfo *appinfo2 = (AppendRelInfo *) lfirst(lc2);
if (bms_is_member(appinfo2->child_relid, modifiableARIindexes))
appinfo2 = (AppendRelInfo *) copyObject(appinfo2);
subroot->append_rel_list = lappend(subroot->append_rel_list,
appinfo2);
}
}
/*
* Add placeholders to the child Query's rangetable list to fill the
* RT indexes already reserved for subqueries in previous children.
* These won't be referenced, so there's no need to make them very
* valid-looking.
*/
while (list_length(subroot->parse->rtable) < list_length(final_rtable))
subroot->parse->rtable = lappend(subroot->parse->rtable,
makeNode(RangeTblEntry));
/*
* If this isn't the first child Query, generate duplicates of all
* subquery (or subquery-to-be) RTEs, and adjust Var numbering to
* reference the duplicates. To simplify the loop logic, we scan the
* original rtable not the copy just made by adjust_appendrel_attrs;
* that should be OK since subquery RTEs couldn't contain any
* references to the target rel.
*/
if (final_rtable != NIL && subqueryRTindexes != NULL)
{
ListCell *lr;
rti = 1;
foreach(lr, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lr);
if (bms_is_member(rti, subqueryRTindexes))
{
Index newrti;
/*
* The RTE can't contain any references to its own RT
* index, except in the security barrier quals, so we can
* save a few cycles by applying ChangeVarNodes before we
* append the RTE to the rangetable.
*/
newrti = list_length(subroot->parse->rtable) + 1;
ChangeVarNodes((Node *) subroot->parse, rti, newrti, 0);
ChangeVarNodes((Node *) subroot->rowMarks, rti, newrti, 0);
/* Skip processing unchanging parts of append_rel_list */
if (modifiableARIindexes != NULL)
{
ListCell *lc2;
foreach(lc2, subroot->append_rel_list)
{
AppendRelInfo *appinfo2 = (AppendRelInfo *) lfirst(lc2);
if (bms_is_member(appinfo2->child_relid,
modifiableARIindexes))
ChangeVarNodes((Node *) appinfo2, rti, newrti, 0);
}
}
rte = copyObject(rte);
ChangeVarNodes((Node *) rte->securityQuals, rti, newrti, 0);
subroot->parse->rtable = lappend(subroot->parse->rtable,
rte);
}
rti++;
}
}
/* There shouldn't be any OJ info to translate, as yet */
Assert(subroot->join_info_list == NIL);
/* and we haven't created PlaceHolderInfos, either */
Assert(subroot->placeholder_list == NIL);
/* hack to mark target relation as an inheritance partition */
subroot->hasInheritedTarget = true;
/* Generate Path(s) for accessing this result relation */
grouping_planner(subroot, true, 0.0 /* retrieve all tuples */ );
/*
* Planning may have modified the query result relation (if there were
* security barrier quals on the result RTE).
*/
appinfo->child_relid = subroot->parse->resultRelation;
/*
* We'll use the first child relation (even if it's excluded) as the
* nominal target relation of the ModifyTable node. Because of the
* way expand_inherited_rtentry works, this should always be the RTE
* representing the parent table in its role as a simple member of the
* inheritance set. (It would be logically cleaner to use the
* inheritance parent RTE as the nominal target; but since that RTE
* will not be otherwise referenced in the plan, doing so would give
* rise to confusing use of multiple aliases in EXPLAIN output for
* what the user will think is the "same" table.)
*/
if (nominalRelation < 0)
nominalRelation = appinfo->child_relid;
/*
* Select cheapest path in case there's more than one. We always run
* modification queries to conclusion, so we care only for the
* cheapest-total path.
*/
sub_final_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);
set_cheapest(sub_final_rel);
subpath = sub_final_rel->cheapest_total_path;
/*
* If this child rel was excluded by constraint exclusion, exclude it
* from the result plan.
*/
if (IS_DUMMY_PATH(subpath))
continue;
/*
* If this is the first non-excluded child, its post-planning rtable
* becomes the initial contents of final_rtable; otherwise, append
* just its modified subquery RTEs to final_rtable.
*/
if (final_rtable == NIL)
final_rtable = subroot->parse->rtable;
else
{
List *tmp_rtable = NIL;
ListCell *cell1,
*cell2;
/*
* Check to see if any of the original RTEs were turned into
* subqueries during planning. Currently, this should only ever
* happen due to securityQuals being involved which push a
* relation down under a subquery, to ensure that the security
* barrier quals are evaluated first.
*
* When this happens, we want to use the new subqueries in the
* final rtable.
*/
forboth(cell1, final_rtable, cell2, subroot->parse->rtable)
{
RangeTblEntry *rte1 = (RangeTblEntry *) lfirst(cell1);
RangeTblEntry *rte2 = (RangeTblEntry *) lfirst(cell2);
if (rte1->rtekind == RTE_RELATION &&
rte2->rtekind == RTE_SUBQUERY)
{
/* Should only be when there are securityQuals today */
Assert(rte1->securityQuals != NIL);
tmp_rtable = lappend(tmp_rtable, rte2);
}
else
tmp_rtable = lappend(tmp_rtable, rte1);
}
final_rtable = list_concat(tmp_rtable,
list_copy_tail(subroot->parse->rtable,
list_length(final_rtable)));
}
/*
* We need to collect all the RelOptInfos from all child plans into
* the main PlannerInfo, since setrefs.c will need them. We use the
* last child's simple_rel_array (previous ones are too short), so we
* have to propagate forward the RelOptInfos that were already built
* in previous children.
*/
Assert(subroot->simple_rel_array_size >= save_rel_array_size);
for (rti = 1; rti < save_rel_array_size; rti++)
{
RelOptInfo *brel = save_rel_array[rti];
if (brel)
subroot->simple_rel_array[rti] = brel;
}
save_rel_array_size = subroot->simple_rel_array_size;
save_rel_array = subroot->simple_rel_array;
/* Make sure any initplans from this rel get into the outer list */
root->init_plans = subroot->init_plans;
/* Build list of sub-paths */
subpaths = lappend(subpaths, subpath);
/* Build list of modified subroots, too */
subroots = lappend(subroots, subroot);
/* Build list of target-relation RT indexes */
resultRelations = lappend_int(resultRelations, appinfo->child_relid);
/* Build lists of per-relation WCO and RETURNING targetlists */
if (parse->withCheckOptions)
withCheckOptionLists = lappend(withCheckOptionLists,
subroot->parse->withCheckOptions);
if (parse->returningList)
returningLists = lappend(returningLists,
subroot->parse->returningList);
Assert(!parse->onConflict);
}
/* Result path must go into outer query's FINAL upperrel */
final_rel = fetch_upper_rel(root, UPPERREL_FINAL, NULL);
/*
* If we managed to exclude every child rel, return a dummy plan; it
* doesn't even need a ModifyTable node.
*/
if (subpaths == NIL)
{
set_dummy_rel_pathlist(final_rel);
return;
}
/*
* Put back the final adjusted rtable into the master copy of the Query.
* (We mustn't do this if we found no non-excluded children.)
*/
parse->rtable = final_rtable;
root->simple_rel_array_size = save_rel_array_size;
root->simple_rel_array = save_rel_array;
/* Must reconstruct master's simple_rte_array, too */
root->simple_rte_array = (RangeTblEntry **)
palloc0((list_length(final_rtable) + 1) * sizeof(RangeTblEntry *));
rti = 1;
foreach(lc, final_rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
root->simple_rte_array[rti++] = rte;
}
/*
* If there was a FOR [KEY] UPDATE/SHARE clause, the LockRows node will
* have dealt with fetching non-locked marked rows, else we need to have
* ModifyTable do that.
*/
if (parse->rowMarks)
rowMarks = NIL;
else
rowMarks = root->rowMarks;
/* Create Path representing a ModifyTable to do the UPDATE/DELETE work */
add_path(final_rel, (Path *)
create_modifytable_path(root, final_rel,
parse->commandType,
parse->canSetTag,
nominalRelation,
resultRelations,
subpaths,
subroots,
withCheckOptionLists,
returningLists,
rowMarks,
NULL,
SS_assign_special_param(root)));
}
/*--------------------
* grouping_planner
* Perform planning steps related to grouping, aggregation, etc.
*
* This function adds all required top-level processing to the scan/join
* Path(s) produced by query_planner.
*
* If inheritance_update is true, we're being called from inheritance_planner
* and should not include a ModifyTable step in the resulting Path(s).
* (inheritance_planner will create a single ModifyTable node covering all the
* target tables.)
*
* tuple_fraction is the fraction of tuples we expect will be retrieved.
* tuple_fraction is interpreted as follows:
* 0: expect all tuples to be retrieved (normal case)
* 0 < tuple_fraction < 1: expect the given fraction of tuples available
* from the plan to be retrieved
* tuple_fraction >= 1: tuple_fraction is the absolute number of tuples
* expected to be retrieved (ie, a LIMIT specification)
*
* Returns nothing; the useful output is in the Paths we attach to the
* (UPPERREL_FINAL, NULL) upperrel in *root. In addition,
* root->processed_tlist contains the final processed targetlist.
*
* Note that we have not done set_cheapest() on the final rel; it's convenient
* to leave this to the caller.
*--------------------
*/
static void
grouping_planner(PlannerInfo *root, bool inheritance_update,
double tuple_fraction)
{
Query *parse = root->parse;
List *tlist = parse->targetList;
int64 offset_est = 0;
int64 count_est = 0;
double limit_tuples = -1.0;
bool have_postponed_srfs = false;
double tlist_rows;
PathTarget *final_target;
RelOptInfo *current_rel;
RelOptInfo *final_rel;
ListCell *lc;
/* Tweak caller-supplied tuple_fraction if have LIMIT/OFFSET */
if (parse->limitCount || parse->limitOffset)
{
tuple_fraction = preprocess_limit(root, tuple_fraction,
&offset_est, &count_est);
/*
* If we have a known LIMIT, and don't have an unknown OFFSET, we can
* estimate the effects of using a bounded sort.
*/
if (count_est > 0 && offset_est >= 0)
limit_tuples = (double) count_est + (double) offset_est;
}
/* Make tuple_fraction accessible to lower-level routines */
root->tuple_fraction = tuple_fraction;
if (parse->setOperations)
{
/*
* If there's a top-level ORDER BY, assume we have to fetch all the
* tuples. This might be too simplistic given all the hackery below
* to possibly avoid the sort; but the odds of accurate estimates here
* are pretty low anyway. XXX try to get rid of this in favor of
* letting plan_set_operations generate both fast-start and
* cheapest-total paths.
*/
if (parse->sortClause)
root->tuple_fraction = 0.0;
/*
* Construct Paths for set operations. The results will not need any
* work except perhaps a top-level sort and/or LIMIT. Note that any
* special work for recursive unions is the responsibility of
* plan_set_operations.
*/
current_rel = plan_set_operations(root);
/*
* We should not need to call preprocess_targetlist, since we must be
* in a SELECT query node. Instead, use the targetlist returned by
* plan_set_operations (since this tells whether it returned any
* resjunk columns!), and transfer any sort key information from the
* original tlist.
*/
Assert(parse->commandType == CMD_SELECT);
tlist = root->processed_tlist; /* from plan_set_operations */
/* for safety, copy processed_tlist instead of modifying in-place */
tlist = postprocess_setop_tlist(copyObject(tlist), parse->targetList);
/* Save aside the final decorated tlist */
root->processed_tlist = tlist;
/* Also extract the PathTarget form of the setop result tlist */
final_target = current_rel->cheapest_total_path->pathtarget;
/*
* Can't handle FOR [KEY] UPDATE/SHARE here (parser should have
* checked already, but let's make sure).
*/
if (parse->rowMarks)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/*------
translator: %s is a SQL row locking clause such as FOR UPDATE */
errmsg("%s is not allowed with UNION/INTERSECT/EXCEPT",
LCS_asString(((RowMarkClause *)
linitial(parse->rowMarks))->strength))));
/*
* Calculate pathkeys that represent result ordering requirements
*/
Assert(parse->distinctClause == NIL);
root->sort_pathkeys = make_pathkeys_for_sortclauses(root,
parse->sortClause,
tlist);
}
else
{
/* No set operations, do regular planning */
PathTarget *sort_input_target;
PathTarget *grouping_target;
PathTarget *scanjoin_target;
bool have_grouping;
WindowFuncLists *wflists = NULL;
List *activeWindows = NIL;
List *rollup_lists = NIL;
List *rollup_groupclauses = NIL;
standard_qp_extra qp_extra;
/* A recursive query should always have setOperations */
Assert(!root->hasRecursion);
/* Preprocess grouping sets and GROUP BY clause, if any */
if (parse->groupingSets)
{
int *tleref_to_colnum_map;
List *sets;
int maxref;
ListCell *lc;
ListCell *lc2;
ListCell *lc_set;
parse->groupingSets = expand_grouping_sets(parse->groupingSets, -1);
/* Identify max SortGroupRef in groupClause, for array sizing */
maxref = 0;
foreach(lc, parse->groupClause)
{
SortGroupClause *gc = lfirst(lc);
if (gc->tleSortGroupRef > maxref)
maxref = gc->tleSortGroupRef;
}
/* Allocate workspace array for remapping */
tleref_to_colnum_map = (int *) palloc((maxref + 1) * sizeof(int));
/* Examine the rollup sets */
sets = extract_rollup_sets(parse->groupingSets);
foreach(lc_set, sets)
{
List *current_sets = (List *) lfirst(lc_set);
List *groupclause;
int ref;
/*
* Reorder the current list of grouping sets into correct
* prefix order. If only one aggregation pass is needed, try
* to make the list match the ORDER BY clause; if more than
* one pass is needed, we don't bother with that.
*/
current_sets = reorder_grouping_sets(current_sets,
(list_length(sets) == 1
? parse->sortClause
: NIL));
/*
* Order the groupClause appropriately. If the first grouping
* set is empty, this can match regular GROUP BY
* preprocessing, otherwise we have to force the groupClause
* to match that grouping set's order.
*/
groupclause = preprocess_groupclause(root,
linitial(current_sets));
/*
* Now that we've pinned down an order for the groupClause for
* this list of grouping sets, we need to remap the entries in
* the grouping sets from sortgrouprefs to plain indices
* (0-based) into the groupClause for this collection of
* grouping sets.
*/
ref = 0;
foreach(lc, groupclause)
{
SortGroupClause *gc = lfirst(lc);
tleref_to_colnum_map[gc->tleSortGroupRef] = ref++;
}
foreach(lc, current_sets)
{
foreach(lc2, (List *) lfirst(lc))
{
lfirst_int(lc2) = tleref_to_colnum_map[lfirst_int(lc2)];
}
}
/* Save the reordered sets and corresponding groupclauses */
rollup_lists = lcons(current_sets, rollup_lists);
rollup_groupclauses = lcons(groupclause, rollup_groupclauses);
}
}
else
{
/* Preprocess regular GROUP BY clause, if any */
if (parse->groupClause)
parse->groupClause = preprocess_groupclause(root, NIL);
}
/* Preprocess targetlist */
tlist = preprocess_targetlist(root, tlist);
if (parse->onConflict)
parse->onConflict->onConflictSet =
preprocess_onconflict_targetlist(parse->onConflict->onConflictSet,
parse->resultRelation,
parse->rtable);
/*
* Expand any rangetable entries that have security barrier quals.
* This may add new security barrier subquery RTEs to the rangetable.
*/
expand_security_quals(root, tlist);
if (parse->hasRowSecurity)
root->glob->hasRowSecurity = true;
/*
* We are now done hacking up the query's targetlist. Most of the
* remaining planning work will be done with the PathTarget
* representation of tlists, but save aside the full representation so
* that we can transfer its decoration (resnames etc) to the topmost
* tlist of the finished Plan.
*/
root->processed_tlist = tlist;
/*
* Locate any window functions in the tlist. (We don't need to look
* anywhere else, since expressions used in ORDER BY will be in there
* too.) Note that they could all have been eliminated by constant
* folding, in which case we don't need to do any more work.
*/
if (parse->hasWindowFuncs)
{
wflists = find_window_functions((Node *) tlist,
list_length(parse->windowClause));
if (wflists->numWindowFuncs > 0)
activeWindows = select_active_windows(root, wflists);
else
parse->hasWindowFuncs = false;
}
/*
* Preprocess MIN/MAX aggregates, if any. Note: be careful about
* adding logic between here and the query_planner() call. Anything
* that is needed in MIN/MAX-optimizable cases will have to be
* duplicated in planagg.c.
*/
if (parse->hasAggs)
preprocess_minmax_aggregates(root, tlist);
/*
* Figure out whether there's a hard limit on the number of rows that
* query_planner's result subplan needs to return. Even if we know a
* hard limit overall, it doesn't apply if the query has any
* grouping/aggregation operations. (XXX it also doesn't apply if the
* tlist contains any SRFs; but checking for that here seems more
* costly than it's worth, since root->limit_tuples is only used for
* cost estimates, and only in a small number of cases.)
*/
if (parse->groupClause ||
parse->groupingSets ||
parse->distinctClause ||
parse->hasAggs ||
parse->hasWindowFuncs ||
root->hasHavingQual)
root->limit_tuples = -1.0;
else
root->limit_tuples = limit_tuples;
/* Set up data needed by standard_qp_callback */
qp_extra.tlist = tlist;
qp_extra.activeWindows = activeWindows;
qp_extra.groupClause =
parse->groupingSets ? llast(rollup_groupclauses) : parse->groupClause;
/*
* Generate the best unsorted and presorted paths for the scan/join
* portion of this Query, ie the processing represented by the
* FROM/WHERE clauses. (Note there may not be any presorted paths.)
* We also generate (in standard_qp_callback) pathkey representations
* of the query's sort clause, distinct clause, etc.
*/
current_rel = query_planner(root, tlist,
standard_qp_callback, &qp_extra);
/*
* Convert the query's result tlist into PathTarget format.
*
* Note: it's desirable to not do this till after query_planner(),
* because the target width estimates can use per-Var width numbers
* that were obtained within query_planner().
*/
final_target = create_pathtarget(root, tlist);
/*
* If ORDER BY was given, consider whether we should use a post-sort
* projection, and compute the adjusted target for preceding steps if
* so.
*/
if (parse->sortClause)
sort_input_target = make_sort_input_target(root,
final_target,
&have_postponed_srfs);
else
sort_input_target = final_target;
/*
* If we have window functions to deal with, the output from any
* grouping step needs to be what the window functions want;
* otherwise, it should be sort_input_target.
*/
if (activeWindows)
grouping_target = make_window_input_target(root,
final_target,
activeWindows);
else
grouping_target = sort_input_target;
/*
* If we have grouping or aggregation to do, the topmost scan/join
* plan node must emit what the grouping step wants; otherwise, it
* should emit grouping_target.
*/
have_grouping = (parse->groupClause || parse->groupingSets ||
parse->hasAggs || root->hasHavingQual);
if (have_grouping)
scanjoin_target = make_group_input_target(root, final_target);
else
scanjoin_target = grouping_target;
/*
* Forcibly apply that target to all the Paths for the scan/join rel.
*
* In principle we should re-run set_cheapest() here to identify the
* cheapest path, but it seems unlikely that adding the same tlist
* eval costs to all the paths would change that, so we don't bother.
* Instead, just assume that the cheapest-startup and cheapest-total
* paths remain so. (There should be no parameterized paths anymore,
* so we needn't worry about updating cheapest_parameterized_paths.)
*/
foreach(lc, current_rel->pathlist)
{
Path *subpath = (Path *) lfirst(lc);
Path *path;
Assert(subpath->param_info == NULL);
path = apply_projection_to_path(root, current_rel,
subpath, scanjoin_target);
/* If we had to add a Result, path is different from subpath */
if (path != subpath)
{
lfirst(lc) = path;
if (subpath == current_rel->cheapest_startup_path)
current_rel->cheapest_startup_path = path;
if (subpath == current_rel->cheapest_total_path)
current_rel->cheapest_total_path = path;
}
}
/*
* Save the various upper-rel PathTargets we just computed into
* root->upper_targets[]. The core code doesn't use this, but it
* provides a convenient place for extensions to get at the info. For
* consistency, we save all the intermediate targets, even though some
* of the corresponding upperrels might not be needed for this query.
*/
root->upper_targets[UPPERREL_FINAL] = final_target;
root->upper_targets[UPPERREL_WINDOW] = sort_input_target;
root->upper_targets[UPPERREL_GROUP_AGG] = grouping_target;
/*
* Let extensions, particularly CustomScan providers, consider
* injecting extension Paths into the query's upperrels, where they
* will compete with the Paths we create below. We pass the final
* scan/join rel because that's not so easily findable from the
* PlannerInfo struct; anything else the hook wants to know should be
* obtainable via "root".
*/
if (create_upper_paths_hook)
(*create_upper_paths_hook) (root, current_rel);
/*
* If we have grouping and/or aggregation, consider ways to implement
* that. We build a new upperrel representing the output of this
* phase.
*/
if (have_grouping)
{
current_rel = create_grouping_paths(root,
current_rel,
grouping_target,
rollup_lists,
rollup_groupclauses);
}
/*
* If we have window functions, consider ways to implement those. We
* build a new upperrel representing the output of this phase.
*/
if (activeWindows)
{
current_rel = create_window_paths(root,
current_rel,
grouping_target,
sort_input_target,
tlist,
wflists,
activeWindows);
}
/*
* If there is a DISTINCT clause, consider ways to implement that. We
* build a new upperrel representing the output of this phase.
*/
if (parse->distinctClause)
{
current_rel = create_distinct_paths(root,
current_rel);
}
} /* end of if (setOperations) */
/*
* If ORDER BY was given, consider ways to implement that, and generate a
* new upperrel containing only paths that emit the correct ordering and
* project the correct final_target. We can apply the original
* limit_tuples limit in sort costing here, but only if there are no
* postponed SRFs.
*/
if (parse->sortClause)
{
current_rel = create_ordered_paths(root,
current_rel,
final_target,
have_postponed_srfs ? -1.0 :
limit_tuples);
}
/*
* If there are set-returning functions in the tlist, scale up the output
* rowcounts of all surviving Paths to account for that. Note that if any
* SRFs appear in sorting or grouping columns, we'll have underestimated
* the numbers of rows passing through earlier steps; but that's such a
* weird usage that it doesn't seem worth greatly complicating matters to
* account for it.
*/
tlist_rows = tlist_returns_set_rows(tlist);
if (tlist_rows > 1)
{
foreach(lc, current_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
/*
* We assume that execution costs of the tlist as such were
* already accounted for. However, it still seems appropriate to
* charge something more for the executor's general costs of
* processing the added tuples. The cost is probably less than
* cpu_tuple_cost, though, so we arbitrarily use half of that.
*/
path->total_cost += path->rows * (tlist_rows - 1) *
cpu_tuple_cost / 2;
path->rows *= tlist_rows;
}
/* No need to run set_cheapest; we're keeping all paths anyway. */
}
/*
* Now we are prepared to build the final-output upperrel. Insert all
* surviving paths, with LockRows, Limit, and/or ModifyTable steps added
* if needed.
*/
final_rel = fetch_upper_rel(root, UPPERREL_FINAL, NULL);
foreach(lc, current_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
/*
* If there is a FOR [KEY] UPDATE/SHARE clause, add the LockRows node.
* (Note: we intentionally test parse->rowMarks not root->rowMarks
* here. If there are only non-locking rowmarks, they should be
* handled by the ModifyTable node instead. However, root->rowMarks
* is what goes into the LockRows node.)
*/
if (parse->rowMarks)
{
path = (Path *) create_lockrows_path(root, final_rel, path,
root->rowMarks,
SS_assign_special_param(root));
}
/*
* If there is a LIMIT/OFFSET clause, add the LIMIT node.
*/
if (limit_needed(parse))
{
path = (Path *) create_limit_path(root, final_rel, path,
parse->limitOffset,
parse->limitCount,
offset_est, count_est);
}
/*
* If this is an INSERT/UPDATE/DELETE, and we're not being called from
* inheritance_planner, add the ModifyTable node.
*/
if (parse->commandType != CMD_SELECT && !inheritance_update)
{
List *withCheckOptionLists;
List *returningLists;
List *rowMarks;
/*
* Set up the WITH CHECK OPTION and RETURNING lists-of-lists, if
* needed.
*/
if (parse->withCheckOptions)
withCheckOptionLists = list_make1(parse->withCheckOptions);
else
withCheckOptionLists = NIL;
if (parse->returningList)
returningLists = list_make1(parse->returningList);
else
returningLists = NIL;
/*
* If there was a FOR [KEY] UPDATE/SHARE clause, the LockRows node
* will have dealt with fetching non-locked marked rows, else we
* need to have ModifyTable do that.
*/
if (parse->rowMarks)
rowMarks = NIL;
else
rowMarks = root->rowMarks;
path = (Path *)
create_modifytable_path(root, final_rel,
parse->commandType,
parse->canSetTag,
parse->resultRelation,
list_make1_int(parse->resultRelation),
list_make1(path),
list_make1(root),
withCheckOptionLists,
returningLists,
rowMarks,
parse->onConflict,
SS_assign_special_param(root));
}
/* And shove it into final_rel */
add_path(final_rel, path);
}
/* Note: currently, we leave it to callers to do set_cheapest() */
}
/*
* Detect whether a plan node is a "dummy" plan created when a relation
* is deemed not to need scanning due to constraint exclusion.
*
* Currently, such dummy plans are Result nodes with constant FALSE
* filter quals (see set_dummy_rel_pathlist and create_append_plan).
*
* XXX this probably ought to be somewhere else, but not clear where.
*/
bool
is_dummy_plan(Plan *plan)
{
if (IsA(plan, Result))
{
List *rcqual = (List *) ((Result *) plan)->resconstantqual;
if (list_length(rcqual) == 1)
{
Const *constqual = (Const *) linitial(rcqual);
if (constqual && IsA(constqual, Const))
{
if (!constqual->constisnull &&
!DatumGetBool(constqual->constvalue))
return true;
}
}
}
return false;
}
/*
* Create a bitmapset of the RT indexes of live base relations
*
* Helper for preprocess_rowmarks ... at this point in the proceedings,
* the only good way to distinguish baserels from appendrel children
* is to see what is in the join tree.
*/
static Bitmapset *
get_base_rel_indexes(Node *jtnode)
{
Bitmapset *result;
if (jtnode == NULL)
return NULL;
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
result = bms_make_singleton(varno);
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
result = NULL;
foreach(l, f->fromlist)
result = bms_join(result,
get_base_rel_indexes(lfirst(l)));
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
result = bms_join(get_base_rel_indexes(j->larg),
get_base_rel_indexes(j->rarg));
}
else
{
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
result = NULL; /* keep compiler quiet */
}
return result;
}
/*
* preprocess_rowmarks - set up PlanRowMarks if needed
*/
static void
preprocess_rowmarks(PlannerInfo *root)
{
Query *parse = root->parse;
Bitmapset *rels;
List *prowmarks;
ListCell *l;
int i;
if (parse->rowMarks)
{
/*
* We've got trouble if FOR [KEY] UPDATE/SHARE appears inside
* grouping, since grouping renders a reference to individual tuple
* CTIDs invalid. This is also checked at parse time, but that's
* insufficient because of rule substitution, query pullup, etc.
*/
CheckSelectLocking(parse, ((RowMarkClause *)
linitial(parse->rowMarks))->strength);
}
else
{
/*
* We only need rowmarks for UPDATE, DELETE, or FOR [KEY]
* UPDATE/SHARE.
*/
if (parse->commandType != CMD_UPDATE &&
parse->commandType != CMD_DELETE)
return;
}
/*
* We need to have rowmarks for all base relations except the target. We
* make a bitmapset of all base rels and then remove the items we don't
* need or have FOR [KEY] UPDATE/SHARE marks for.
*/
rels = get_base_rel_indexes((Node *) parse->jointree);
if (parse->resultRelation)
rels = bms_del_member(rels, parse->resultRelation);
/*
* Convert RowMarkClauses to PlanRowMark representation.
*/
prowmarks = NIL;
foreach(l, parse->rowMarks)
{
RowMarkClause *rc = (RowMarkClause *) lfirst(l);
RangeTblEntry *rte = rt_fetch(rc->rti, parse->rtable);
PlanRowMark *newrc;
/*
* Currently, it is syntactically impossible to have FOR UPDATE et al
* applied to an update/delete target rel. If that ever becomes
* possible, we should drop the target from the PlanRowMark list.
*/
Assert(rc->rti != parse->resultRelation);
/*
* Ignore RowMarkClauses for subqueries; they aren't real tables and
* can't support true locking. Subqueries that got flattened into the
* main query should be ignored completely. Any that didn't will get
* ROW_MARK_COPY items in the next loop.
*/
if (rte->rtekind != RTE_RELATION)
continue;
rels = bms_del_member(rels, rc->rti);
newrc = makeNode(PlanRowMark);
newrc->rti = newrc->prti = rc->rti;
newrc->rowmarkId = ++(root->glob->lastRowMarkId);
newrc->markType = select_rowmark_type(rte, rc->strength);
newrc->allMarkTypes = (1 << newrc->markType);
newrc->strength = rc->strength;
newrc->waitPolicy = rc->waitPolicy;
newrc->isParent = false;
prowmarks = lappend(prowmarks, newrc);
}
/*
* Now, add rowmarks for any non-target, non-locked base relations.
*/
i = 0;
foreach(l, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(l);
PlanRowMark *newrc;
i++;
if (!bms_is_member(i, rels))
continue;
newrc = makeNode(PlanRowMark);
newrc->rti = newrc->prti = i;
newrc->rowmarkId = ++(root->glob->lastRowMarkId);
newrc->markType = select_rowmark_type(rte, LCS_NONE);
newrc->allMarkTypes = (1 << newrc->markType);
newrc->strength = LCS_NONE;
newrc->waitPolicy = LockWaitBlock; /* doesn't matter */
newrc->isParent = false;
prowmarks = lappend(prowmarks, newrc);
}
root->rowMarks = prowmarks;
}
/*
* Select RowMarkType to use for a given table
*/
RowMarkType
select_rowmark_type(RangeTblEntry *rte, LockClauseStrength strength)
{
if (rte->rtekind != RTE_RELATION)
{
/* If it's not a table at all, use ROW_MARK_COPY */
return ROW_MARK_COPY;
}
else if (rte->relkind == RELKIND_FOREIGN_TABLE)
{
/* Let the FDW select the rowmark type, if it wants to */
FdwRoutine *fdwroutine = GetFdwRoutineByRelId(rte->relid);
if (fdwroutine->GetForeignRowMarkType != NULL)
return fdwroutine->GetForeignRowMarkType(rte, strength);
/* Otherwise, use ROW_MARK_COPY by default */
return ROW_MARK_COPY;
}
else
{
/* Regular table, apply the appropriate lock type */
switch (strength)
{
case LCS_NONE:
/*
* We don't need a tuple lock, only the ability to re-fetch
* the row. Regular tables support ROW_MARK_REFERENCE, but if
* this RTE has security barrier quals, it will be turned into
* a subquery during planning, so use ROW_MARK_COPY.
*
* This is only necessary for LCS_NONE, since real tuple locks
* on an RTE with security barrier quals are supported by
* pushing the lock down into the subquery --- see
* expand_security_qual.
*/
if (rte->securityQuals != NIL)
return ROW_MARK_COPY;
return ROW_MARK_REFERENCE;
break;
case LCS_FORKEYSHARE:
return ROW_MARK_KEYSHARE;
break;
case LCS_FORSHARE:
return ROW_MARK_SHARE;
break;
case LCS_FORNOKEYUPDATE:
return ROW_MARK_NOKEYEXCLUSIVE;
break;
case LCS_FORUPDATE:
return ROW_MARK_EXCLUSIVE;
break;
}
elog(ERROR, "unrecognized LockClauseStrength %d", (int) strength);
return ROW_MARK_EXCLUSIVE; /* keep compiler quiet */
}
}
/*
* preprocess_limit - do pre-estimation for LIMIT and/or OFFSET clauses
*
* We try to estimate the values of the LIMIT/OFFSET clauses, and pass the
* results back in *count_est and *offset_est. These variables are set to
* 0 if the corresponding clause is not present, and -1 if it's present
* but we couldn't estimate the value for it. (The "0" convention is OK
* for OFFSET but a little bit bogus for LIMIT: effectively we estimate
* LIMIT 0 as though it were LIMIT 1. But this is in line with the planner's
* usual practice of never estimating less than one row.) These values will
* be passed to create_limit_path, which see if you change this code.
*
* The return value is the suitably adjusted tuple_fraction to use for
* planning the query. This adjustment is not overridable, since it reflects
* plan actions that grouping_planner() will certainly take, not assumptions
* about context.
*/
static double
preprocess_limit(PlannerInfo *root, double tuple_fraction,
int64 *offset_est, int64 *count_est)
{
Query *parse = root->parse;
Node *est;
double limit_fraction;
/* Should not be called unless LIMIT or OFFSET */
Assert(parse->limitCount || parse->limitOffset);
/*
* Try to obtain the clause values. We use estimate_expression_value
* primarily because it can sometimes do something useful with Params.
*/
if (parse->limitCount)
{
est = estimate_expression_value(root, parse->limitCount);
if (est && IsA(est, Const))
{
if (((Const *) est)->constisnull)
{
/* NULL indicates LIMIT ALL, ie, no limit */
*count_est = 0; /* treat as not present */
}
else
{
*count_est = DatumGetInt64(((Const *) est)->constvalue);
if (*count_est <= 0)
*count_est = 1; /* force to at least 1 */
}
}
else
*count_est = -1; /* can't estimate */
}
else
*count_est = 0; /* not present */
if (parse->limitOffset)
{
est = estimate_expression_value(root, parse->limitOffset);
if (est && IsA(est, Const))
{
if (((Const *) est)->constisnull)
{
/* Treat NULL as no offset; the executor will too */
*offset_est = 0; /* treat as not present */
}
else
{
*offset_est = DatumGetInt64(((Const *) est)->constvalue);
if (*offset_est < 0)
*offset_est = 0; /* treat as not present */
}
}
else
*offset_est = -1; /* can't estimate */
}
else
*offset_est = 0; /* not present */
if (*count_est != 0)
{
/*
* A LIMIT clause limits the absolute number of tuples returned.
* However, if it's not a constant LIMIT then we have to guess; for
* lack of a better idea, assume 10% of the plan's result is wanted.
*/
if (*count_est < 0 || *offset_est < 0)
{
/* LIMIT or OFFSET is an expression ... punt ... */
limit_fraction = 0.10;
}
else
{
/* LIMIT (plus OFFSET, if any) is max number of tuples needed */
limit_fraction = (double) *count_est + (double) *offset_est;
}
/*
* If we have absolute limits from both caller and LIMIT, use the
* smaller value; likewise if they are both fractional. If one is
* fractional and the other absolute, we can't easily determine which
* is smaller, but we use the heuristic that the absolute will usually
* be smaller.
*/
if (tuple_fraction >= 1.0)
{
if (limit_fraction >= 1.0)
{
/* both absolute */
tuple_fraction = Min(tuple_fraction, limit_fraction);
}
else
{
/* caller absolute, limit fractional; use caller's value */
}
}
else if (tuple_fraction > 0.0)
{
if (limit_fraction >= 1.0)
{
/* caller fractional, limit absolute; use limit */
tuple_fraction = limit_fraction;
}
else
{
/* both fractional */
tuple_fraction = Min(tuple_fraction, limit_fraction);
}
}
else
{
/* no info from caller, just use limit */
tuple_fraction = limit_fraction;
}
}
else if (*offset_est != 0 && tuple_fraction > 0.0)
{
/*
* We have an OFFSET but no LIMIT. This acts entirely differently
* from the LIMIT case: here, we need to increase rather than decrease
* the caller's tuple_fraction, because the OFFSET acts to cause more
* tuples to be fetched instead of fewer. This only matters if we got
* a tuple_fraction > 0, however.
*
* As above, use 10% if OFFSET is present but unestimatable.
*/
if (*offset_est < 0)
limit_fraction = 0.10;
else
limit_fraction = (double) *offset_est;
/*
* If we have absolute counts from both caller and OFFSET, add them
* together; likewise if they are both fractional. If one is
* fractional and the other absolute, we want to take the larger, and
* we heuristically assume that's the fractional one.
*/
if (tuple_fraction >= 1.0)
{
if (limit_fraction >= 1.0)
{
/* both absolute, so add them together */
tuple_fraction += limit_fraction;
}
else
{
/* caller absolute, limit fractional; use limit */
tuple_fraction = limit_fraction;
}
}
else
{
if (limit_fraction >= 1.0)
{
/* caller fractional, limit absolute; use caller's value */
}
else
{
/* both fractional, so add them together */
tuple_fraction += limit_fraction;
if (tuple_fraction >= 1.0)
tuple_fraction = 0.0; /* assume fetch all */
}
}
}
return tuple_fraction;
}
/*
* limit_needed - do we actually need a Limit plan node?
*
* If we have constant-zero OFFSET and constant-null LIMIT, we can skip adding
* a Limit node. This is worth checking for because "OFFSET 0" is a common
* locution for an optimization fence. (Because other places in the planner
* merely check whether parse->limitOffset isn't NULL, it will still work as
* an optimization fence --- we're just suppressing unnecessary run-time
* overhead.)
*
* This might look like it could be merged into preprocess_limit, but there's
* a key distinction: here we need hard constants in OFFSET/LIMIT, whereas
* in preprocess_limit it's good enough to consider estimated values.
*/
static bool
limit_needed(Query *parse)
{
Node *node;
node = parse->limitCount;
if (node)
{
if (IsA(node, Const))
{
/* NULL indicates LIMIT ALL, ie, no limit */
if (!((Const *) node)->constisnull)
return true; /* LIMIT with a constant value */
}
else
return true; /* non-constant LIMIT */
}
node = parse->limitOffset;
if (node)
{
if (IsA(node, Const))
{
/* Treat NULL as no offset; the executor would too */
if (!((Const *) node)->constisnull)
{
int64 offset = DatumGetInt64(((Const *) node)->constvalue);
if (offset != 0)
return true; /* OFFSET with a nonzero value */
}
}
else
return true; /* non-constant OFFSET */
}
return false; /* don't need a Limit plan node */
}
/*
* remove_useless_groupby_columns
* Remove any columns in the GROUP BY clause that are redundant due to
* being functionally dependent on other GROUP BY columns.
*
* Since some other DBMSes do not allow references to ungrouped columns, it's
* not unusual to find all columns listed in GROUP BY even though listing the
* primary-key columns would be sufficient. Deleting such excess columns
* avoids redundant sorting work, so it's worth doing. When we do this, we
* must mark the plan as dependent on the pkey constraint (compare the
* parser's check_ungrouped_columns() and check_functional_grouping()).
*
* In principle, we could treat any NOT-NULL columns appearing in a UNIQUE
* index as the determining columns. But as with check_functional_grouping(),
* there's currently no way to represent dependency on a NOT NULL constraint,
* so we consider only the pkey for now.
*/
static void
remove_useless_groupby_columns(PlannerInfo *root)
{
Query *parse = root->parse;
Bitmapset **groupbyattnos;
Bitmapset **surplusvars;
ListCell *lc;
int relid;
/* No chance to do anything if there are less than two GROUP BY items */
if (list_length(parse->groupClause) < 2)
return;
/* Don't fiddle with the GROUP BY clause if the query has grouping sets */
if (parse->groupingSets)
return;
/*
* Scan the GROUP BY clause to find GROUP BY items that are simple Vars.
* Fill groupbyattnos[k] with a bitmapset of the column attnos of RTE k
* that are GROUP BY items.
*/
groupbyattnos = (Bitmapset **) palloc0(sizeof(Bitmapset *) *
(list_length(parse->rtable) + 1));
foreach(lc, parse->groupClause)
{
SortGroupClause *sgc = (SortGroupClause *) lfirst(lc);
TargetEntry *tle = get_sortgroupclause_tle(sgc, parse->targetList);
Var *var = (Var *) tle->expr;
/*
* Ignore non-Vars and Vars from other query levels.
*
* XXX in principle, stable expressions containing Vars could also be
* removed, if all the Vars are functionally dependent on other GROUP
* BY items. But it's not clear that such cases occur often enough to
* be worth troubling over.
*/
if (!IsA(var, Var) ||
var->varlevelsup > 0)
continue;
/* OK, remember we have this Var */
relid = var->varno;
Assert(relid <= list_length(parse->rtable));
groupbyattnos[relid] = bms_add_member(groupbyattnos[relid],
var->varattno - FirstLowInvalidHeapAttributeNumber);
}
/*
* Consider each relation and see if it is possible to remove some of its
* Vars from GROUP BY. For simplicity and speed, we do the actual removal
* in a separate pass. Here, we just fill surplusvars[k] with a bitmapset
* of the column attnos of RTE k that are removable GROUP BY items.
*/
surplusvars = NULL; /* don't allocate array unless required */
relid = 0;
foreach(lc, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
Bitmapset *relattnos;
Bitmapset *pkattnos;
Oid constraintOid;
relid++;
/* Only plain relations could have primary-key constraints */
if (rte->rtekind != RTE_RELATION)
continue;
/* Nothing to do unless this rel has multiple Vars in GROUP BY */
relattnos = groupbyattnos[relid];
if (bms_membership(relattnos) != BMS_MULTIPLE)
continue;
/*
* Can't remove any columns for this rel if there is no suitable
* (i.e., nondeferrable) primary key constraint.
*/
pkattnos = get_primary_key_attnos(rte->relid, false, &constraintOid);
if (pkattnos == NULL)
continue;
/*
* If the primary key is a proper subset of relattnos then we have
* some items in the GROUP BY that can be removed.
*/
if (bms_subset_compare(pkattnos, relattnos) == BMS_SUBSET1)
{
/*
* To easily remember whether we've found anything to do, we don't
* allocate the surplusvars[] array until we find something.
*/
if (surplusvars == NULL)
surplusvars = (Bitmapset **) palloc0(sizeof(Bitmapset *) *
(list_length(parse->rtable) + 1));
/* Remember the attnos of the removable columns */
surplusvars[relid] = bms_difference(relattnos, pkattnos);
/* Also, mark the resulting plan as dependent on this constraint */
parse->constraintDeps = lappend_oid(parse->constraintDeps,
constraintOid);
}
}
/*
* If we found any surplus Vars, build a new GROUP BY clause without them.
* (Note: this may leave some TLEs with unreferenced ressortgroupref
* markings, but that's harmless.)
*/
if (surplusvars != NULL)
{
List *new_groupby = NIL;
foreach(lc, parse->groupClause)
{
SortGroupClause *sgc = (SortGroupClause *) lfirst(lc);
TargetEntry *tle = get_sortgroupclause_tle(sgc, parse->targetList);
Var *var = (Var *) tle->expr;
/*
* New list must include non-Vars, outer Vars, and anything not
* marked as surplus.
*/
if (!IsA(var, Var) ||
var->varlevelsup > 0 ||
!bms_is_member(var->varattno - FirstLowInvalidHeapAttributeNumber,
surplusvars[var->varno]))
new_groupby = lappend(new_groupby, sgc);
}
parse->groupClause = new_groupby;
}
}
/*
* preprocess_groupclause - do preparatory work on GROUP BY clause
*
* The idea here is to adjust the ordering of the GROUP BY elements
* (which in itself is semantically insignificant) to match ORDER BY,
* thereby allowing a single sort operation to both implement the ORDER BY
* requirement and set up for a Unique step that implements GROUP BY.
*
* In principle it might be interesting to consider other orderings of the
* GROUP BY elements, which could match the sort ordering of other
* possible plans (eg an indexscan) and thereby reduce cost. We don't
* bother with that, though. Hashed grouping will frequently win anyway.
*
* Note: we need no comparable processing of the distinctClause because
* the parser already enforced that that matches ORDER BY.
*
* For grouping sets, the order of items is instead forced to agree with that
* of the grouping set (and items not in the grouping set are skipped). The
* work of sorting the order of grouping set elements to match the ORDER BY if
* possible is done elsewhere.
*/
static List *
preprocess_groupclause(PlannerInfo *root, List *force)
{
Query *parse = root->parse;
List *new_groupclause = NIL;
bool partial_match;
ListCell *sl;
ListCell *gl;
/* For grouping sets, we need to force the ordering */
if (force)
{
foreach(sl, force)
{
Index ref = lfirst_int(sl);
SortGroupClause *cl = get_sortgroupref_clause(ref, parse->groupClause);
new_groupclause = lappend(new_groupclause, cl);
}
return new_groupclause;
}
/* If no ORDER BY, nothing useful to do here */
if (parse->sortClause == NIL)
return parse->groupClause;
/*
* Scan the ORDER BY clause and construct a list of matching GROUP BY
* items, but only as far as we can make a matching prefix.
*
* This code assumes that the sortClause contains no duplicate items.
*/
foreach(sl, parse->sortClause)
{
SortGroupClause *sc = (SortGroupClause *) lfirst(sl);
foreach(gl, parse->groupClause)
{
SortGroupClause *gc = (SortGroupClause *) lfirst(gl);
if (equal(gc, sc))
{
new_groupclause = lappend(new_groupclause, gc);
break;
}
}
if (gl == NULL)
break; /* no match, so stop scanning */
}
/* Did we match all of the ORDER BY list, or just some of it? */
partial_match = (sl != NULL);
/* If no match at all, no point in reordering GROUP BY */
if (new_groupclause == NIL)
return parse->groupClause;
/*
* Add any remaining GROUP BY items to the new list, but only if we were
* able to make a complete match. In other words, we only rearrange the
* GROUP BY list if the result is that one list is a prefix of the other
* --- otherwise there's no possibility of a common sort. Also, give up
* if there are any non-sortable GROUP BY items, since then there's no
* hope anyway.
*/
foreach(gl, parse->groupClause)
{
SortGroupClause *gc = (SortGroupClause *) lfirst(gl);
if (list_member_ptr(new_groupclause, gc))
continue; /* it matched an ORDER BY item */
if (partial_match)
return parse->groupClause; /* give up, no common sort possible */
if (!OidIsValid(gc->sortop))
return parse->groupClause; /* give up, GROUP BY can't be sorted */
new_groupclause = lappend(new_groupclause, gc);
}
/* Success --- install the rearranged GROUP BY list */
Assert(list_length(parse->groupClause) == list_length(new_groupclause));
return new_groupclause;
}
/*
* Extract lists of grouping sets that can be implemented using a single
* rollup-type aggregate pass each. Returns a list of lists of grouping sets.
*
* Input must be sorted with smallest sets first. Result has each sublist
* sorted with smallest sets first.
*
* We want to produce the absolute minimum possible number of lists here to
* avoid excess sorts. Fortunately, there is an algorithm for this; the problem
* of finding the minimal partition of a partially-ordered set into chains
* (which is what we need, taking the list of grouping sets as a poset ordered
* by set inclusion) can be mapped to the problem of finding the maximum
* cardinality matching on a bipartite graph, which is solvable in polynomial
* time with a worst case of no worse than O(n^2.5) and usually much
* better. Since our N is at most 4096, we don't need to consider fallbacks to
* heuristic or approximate methods. (Planning time for a 12-d cube is under
* half a second on my modest system even with optimization off and assertions
* on.)
*/
static List *
extract_rollup_sets(List *groupingSets)
{
int num_sets_raw = list_length(groupingSets);
int num_empty = 0;
int num_sets = 0; /* distinct sets */
int num_chains = 0;
List *result = NIL;
List **results;
List **orig_sets;
Bitmapset **set_masks;
int *chains;
short **adjacency;
short *adjacency_buf;
BipartiteMatchState *state;
int i;
int j;
int j_size;
ListCell *lc1 = list_head(groupingSets);
ListCell *lc;
/*
* Start by stripping out empty sets. The algorithm doesn't require this,
* but the planner currently needs all empty sets to be returned in the
* first list, so we strip them here and add them back after.
*/
while (lc1 && lfirst(lc1) == NIL)
{
++num_empty;
lc1 = lnext(lc1);
}
/* bail out now if it turns out that all we had were empty sets. */
if (!lc1)
return list_make1(groupingSets);
/*----------
* We don't strictly need to remove duplicate sets here, but if we don't,
* they tend to become scattered through the result, which is a bit
* confusing (and irritating if we ever decide to optimize them out).
* So we remove them here and add them back after.
*
* For each non-duplicate set, we fill in the following:
*
* orig_sets[i] = list of the original set lists
* set_masks[i] = bitmapset for testing inclusion
* adjacency[i] = array [n, v1, v2, ... vn] of adjacency indices
*
* chains[i] will be the result group this set is assigned to.
*
* We index all of these from 1 rather than 0 because it is convenient
* to leave 0 free for the NIL node in the graph algorithm.
*----------
*/
orig_sets = palloc0((num_sets_raw + 1) * sizeof(List *));
set_masks = palloc0((num_sets_raw + 1) * sizeof(Bitmapset *));
adjacency = palloc0((num_sets_raw + 1) * sizeof(short *));
adjacency_buf = palloc((num_sets_raw + 1) * sizeof(short));
j_size = 0;
j = 0;
i = 1;
for_each_cell(lc, lc1)
{
List *candidate = lfirst(lc);
Bitmapset *candidate_set = NULL;
ListCell *lc2;
int dup_of = 0;
foreach(lc2, candidate)
{
candidate_set = bms_add_member(candidate_set, lfirst_int(lc2));
}
/* we can only be a dup if we're the same length as a previous set */
if (j_size == list_length(candidate))
{
int k;
for (k = j; k < i; ++k)
{
if (bms_equal(set_masks[k], candidate_set))
{
dup_of = k;
break;
}
}
}
else if (j_size < list_length(candidate))
{
j_size = list_length(candidate);
j = i;
}
if (dup_of > 0)
{
orig_sets[dup_of] = lappend(orig_sets[dup_of], candidate);
bms_free(candidate_set);
}
else
{
int k;
int n_adj = 0;
orig_sets[i] = list_make1(candidate);
set_masks[i] = candidate_set;
/* fill in adjacency list; no need to compare equal-size sets */
for (k = j - 1; k > 0; --k)
{
if (bms_is_subset(set_masks[k], candidate_set))
adjacency_buf[++n_adj] = k;
}
if (n_adj > 0)
{
adjacency_buf[0] = n_adj;
adjacency[i] = palloc((n_adj + 1) * sizeof(short));
memcpy(adjacency[i], adjacency_buf, (n_adj + 1) * sizeof(short));
}
else
adjacency[i] = NULL;
++i;
}
}
num_sets = i - 1;
/*
* Apply the graph matching algorithm to do the work.
*/
state = BipartiteMatch(num_sets, num_sets, adjacency);
/*
* Now, the state->pair* fields have the info we need to assign sets to
* chains. Two sets (u,v) belong to the same chain if pair_uv[u] = v or
* pair_vu[v] = u (both will be true, but we check both so that we can do
* it in one pass)
*/
chains = palloc0((num_sets + 1) * sizeof(int));
for (i = 1; i <= num_sets; ++i)
{
int u = state->pair_vu[i];
int v = state->pair_uv[i];
if (u > 0 && u < i)
chains[i] = chains[u];
else if (v > 0 && v < i)
chains[i] = chains[v];
else
chains[i] = ++num_chains;
}
/* build result lists. */
results = palloc0((num_chains + 1) * sizeof(List *));
for (i = 1; i <= num_sets; ++i)
{
int c = chains[i];
Assert(c > 0);
results[c] = list_concat(results[c], orig_sets[i]);
}
/* push any empty sets back on the first list. */
while (num_empty-- > 0)
results[1] = lcons(NIL, results[1]);
/* make result list */
for (i = 1; i <= num_chains; ++i)
result = lappend(result, results[i]);
/*
* Free all the things.
*
* (This is over-fussy for small sets but for large sets we could have
* tied up a nontrivial amount of memory.)
*/
BipartiteMatchFree(state);
pfree(results);
pfree(chains);
for (i = 1; i <= num_sets; ++i)
if (adjacency[i])
pfree(adjacency[i]);
pfree(adjacency);
pfree(adjacency_buf);
pfree(orig_sets);
for (i = 1; i <= num_sets; ++i)
bms_free(set_masks[i]);
pfree(set_masks);
return result;
}
/*
* Reorder the elements of a list of grouping sets such that they have correct
* prefix relationships.
*
* The input must be ordered with smallest sets first; the result is returned
* with largest sets first. Note that the result shares no list substructure
* with the input, so it's safe for the caller to modify it later.
*
* If we're passed in a sortclause, we follow its order of columns to the
* extent possible, to minimize the chance that we add unnecessary sorts.
* (We're trying here to ensure that GROUPING SETS ((a,b,c),(c)) ORDER BY c,b,a
* gets implemented in one pass.)
*/
static List *
reorder_grouping_sets(List *groupingsets, List *sortclause)
{
ListCell *lc;
ListCell *lc2;
List *previous = NIL;
List *result = NIL;
foreach(lc, groupingsets)
{
List *candidate = lfirst(lc);
List *new_elems = list_difference_int(candidate, previous);
if (list_length(new_elems) > 0)
{
while (list_length(sortclause) > list_length(previous))
{
SortGroupClause *sc = list_nth(sortclause, list_length(previous));
int ref = sc->tleSortGroupRef;
if (list_member_int(new_elems, ref))
{
previous = lappend_int(previous, ref);
new_elems = list_delete_int(new_elems, ref);
}
else
{
/* diverged from the sortclause; give up on it */
sortclause = NIL;
break;
}
}
foreach(lc2, new_elems)
{
previous = lappend_int(previous, lfirst_int(lc2));
}
}
result = lcons(list_copy(previous), result);
list_free(new_elems);
}
list_free(previous);
return result;
}
/*
* Compute query_pathkeys and other pathkeys during plan generation
*/
static void
standard_qp_callback(PlannerInfo *root, void *extra)
{
Query *parse = root->parse;
standard_qp_extra *qp_extra = (standard_qp_extra *) extra;
List *tlist = qp_extra->tlist;
List *activeWindows = qp_extra->activeWindows;
/*
* Calculate pathkeys that represent grouping/ordering requirements. The
* sortClause is certainly sort-able, but GROUP BY and DISTINCT might not
* be, in which case we just leave their pathkeys empty.
*/
if (qp_extra->groupClause &&
grouping_is_sortable(qp_extra->groupClause))
root->group_pathkeys =
make_pathkeys_for_sortclauses(root,
qp_extra->groupClause,
tlist);
else
root->group_pathkeys = NIL;
/* We consider only the first (bottom) window in pathkeys logic */
if (activeWindows != NIL)
{
WindowClause *wc = (WindowClause *) linitial(activeWindows);
root->window_pathkeys = make_pathkeys_for_window(root,
wc,
tlist);
}
else
root->window_pathkeys = NIL;
if (parse->distinctClause &&
grouping_is_sortable(parse->distinctClause))
root->distinct_pathkeys =
make_pathkeys_for_sortclauses(root,
parse->distinctClause,
tlist);
else
root->distinct_pathkeys = NIL;
root->sort_pathkeys =
make_pathkeys_for_sortclauses(root,
parse->sortClause,
tlist);
/*
* Figure out whether we want a sorted result from query_planner.
*
* If we have a sortable GROUP BY clause, then we want a result sorted
* properly for grouping. Otherwise, if we have window functions to
* evaluate, we try to sort for the first window. Otherwise, if there's a
* sortable DISTINCT clause that's more rigorous than the ORDER BY clause,
* we try to produce output that's sufficiently well sorted for the
* DISTINCT. Otherwise, if there is an ORDER BY clause, we want to sort
* by the ORDER BY clause.
*
* Note: if we have both ORDER BY and GROUP BY, and ORDER BY is a superset
* of GROUP BY, it would be tempting to request sort by ORDER BY --- but
* that might just leave us failing to exploit an available sort order at
* all. Needs more thought. The choice for DISTINCT versus ORDER BY is
* much easier, since we know that the parser ensured that one is a
* superset of the other.
*/
if (root->group_pathkeys)
root->query_pathkeys = root->group_pathkeys;
else if (root->window_pathkeys)
root->query_pathkeys = root->window_pathkeys;
else if (list_length(root->distinct_pathkeys) >
list_length(root->sort_pathkeys))
root->query_pathkeys = root->distinct_pathkeys;
else if (root->sort_pathkeys)
root->query_pathkeys = root->sort_pathkeys;
else
root->query_pathkeys = NIL;
}
/*
* Estimate number of groups produced by grouping clauses (1 if not grouping)
*
* path_rows: number of output rows from scan/join step
* rollup_lists: list of grouping sets, or NIL if not doing grouping sets
* rollup_groupclauses: list of grouping clauses for grouping sets,
* or NIL if not doing grouping sets
*/
static double
get_number_of_groups(PlannerInfo *root,
double path_rows,
List *rollup_lists,
List *rollup_groupclauses)
{
Query *parse = root->parse;
double dNumGroups;
if (parse->groupClause)
{
List *groupExprs;
if (parse->groupingSets)
{
/* Add up the estimates for each grouping set */
ListCell *lc,
*lc2;
dNumGroups = 0;
forboth(lc, rollup_groupclauses, lc2, rollup_lists)
{
List *groupClause = (List *) lfirst(lc);
List *gsets = (List *) lfirst(lc2);
ListCell *lc3;
groupExprs = get_sortgrouplist_exprs(groupClause,
parse->targetList);
foreach(lc3, gsets)
{
List *gset = (List *) lfirst(lc3);
dNumGroups += estimate_num_groups(root,
groupExprs,
path_rows,
&gset);
}
}
}
else
{
/* Plain GROUP BY */
groupExprs = get_sortgrouplist_exprs(parse->groupClause,
parse->targetList);
dNumGroups = estimate_num_groups(root, groupExprs, path_rows,
NULL);
}
}
else if (parse->groupingSets)
{
/* Empty grouping sets ... one result row for each one */
dNumGroups = list_length(parse->groupingSets);
}
else if (parse->hasAggs || root->hasHavingQual)
{
/* Plain aggregation, one result row */
dNumGroups = 1;
}
else
{
/* Not grouping */
dNumGroups = 1;
}
return dNumGroups;
}
/*
* create_grouping_paths
*
* Build a new upperrel containing Paths for grouping and/or aggregation.
*
* input_rel: contains the source-data Paths
* target: the pathtarget for the result Paths to compute
* rollup_lists: list of grouping sets, or NIL if not doing grouping sets
* rollup_groupclauses: list of grouping clauses for grouping sets,
* or NIL if not doing grouping sets
*
* Note: all Paths in input_rel are expected to return the target computed
* by make_group_input_target.
*
* We need to consider sorted and hashed aggregation in the same function,
* because otherwise (1) it would be harder to throw an appropriate error
* message if neither way works, and (2) we should not allow enable_hashagg or
* hashtable size considerations to dissuade us from using hashing if sorting
* is not possible.
*/
static RelOptInfo *
create_grouping_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
List *rollup_lists,
List *rollup_groupclauses)
{
Query *parse = root->parse;
Path *cheapest_path = input_rel->cheapest_total_path;
RelOptInfo *grouped_rel;
AggClauseCosts agg_costs;
double dNumGroups;
bool allow_hash;
ListCell *lc;
/* For now, do all work in the (GROUP_AGG, NULL) upperrel */
grouped_rel = fetch_upper_rel(root, UPPERREL_GROUP_AGG, NULL);
/*
* Check for degenerate grouping.
*/
if ((root->hasHavingQual || parse->groupingSets) &&
!parse->hasAggs && parse->groupClause == NIL)
{
/*
* We have a HAVING qual and/or grouping sets, but no aggregates and
* no GROUP BY (which implies that the grouping sets are all empty).
*
* This is a degenerate case in which we are supposed to emit either
* zero or one row for each grouping set depending on whether HAVING
* succeeds. Furthermore, there cannot be any variables in either
* HAVING or the targetlist, so we actually do not need the FROM table
* at all! We can just throw away the plan-so-far and generate a
* Result node. This is a sufficiently unusual corner case that it's
* not worth contorting the structure of this module to avoid having
* to generate the earlier paths in the first place.
*/
int nrows = list_length(parse->groupingSets);
Path *path;
if (nrows > 1)
{
/*
* Doesn't seem worthwhile writing code to cons up a
* generate_series or a values scan to emit multiple rows. Instead
* just make N clones and append them. (With a volatile HAVING
* clause, this means you might get between 0 and N output rows.
* Offhand I think that's desired.)
*/
List *paths = NIL;
while (--nrows >= 0)
{
path = (Path *)
create_result_path(root, grouped_rel,
target,
(List *) parse->havingQual);
paths = lappend(paths, path);
}
path = (Path *)
create_append_path(grouped_rel,
paths,
NULL,
0);
path->pathtarget = target;
}
else
{
/* No grouping sets, or just one, so one output row */
path = (Path *)
create_result_path(root, grouped_rel,
target,
(List *) parse->havingQual);
}
add_path(grouped_rel, path);
/* No need to consider any other alternatives. */
set_cheapest(grouped_rel);
return grouped_rel;
}
/*
* Collect statistics about aggregates for estimating costs. Note: we do
* not detect duplicate aggregates here; a somewhat-overestimated cost is
* okay for our purposes.
*/
MemSet(&agg_costs, 0, sizeof(AggClauseCosts));
if (parse->hasAggs)
{
count_agg_clauses(root, (Node *) target->exprs, &agg_costs);
count_agg_clauses(root, parse->havingQual, &agg_costs);
}
/*
* Estimate number of groups. Note: if cheapest_path is a dummy, it will
* have zero rowcount estimate, which we don't want to use for fear of
* divide-by-zero. Hence clamp.
*/
dNumGroups = get_number_of_groups(root,
clamp_row_est(cheapest_path->rows),
rollup_lists,
rollup_groupclauses);
/*
* Consider sort-based implementations of grouping, if possible. (Note
* that if groupClause is empty, grouping_is_sortable() is trivially true,
* and all the pathkeys_contained_in() tests will succeed too, so that
* we'll consider every surviving input path.)
*/
if (grouping_is_sortable(parse->groupClause))
{
/*
* Use any available suitably-sorted path as input, and also consider
* sorting the cheapest-total path.
*/
foreach(lc, input_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
bool is_sorted;
is_sorted = pathkeys_contained_in(root->group_pathkeys,
path->pathkeys);
if (path == cheapest_path || is_sorted)
{
/* Sort the cheapest-total path if it isn't already sorted */
if (!is_sorted)
path = (Path *) create_sort_path(root,
grouped_rel,
path,
root->group_pathkeys,
-1.0);
/* Now decide what to stick atop it */
if (parse->groupingSets)
{
/*
* We have grouping sets, possibly with aggregation. Make
* a GroupingSetsPath.
*/
add_path(grouped_rel, (Path *)
create_groupingsets_path(root,
grouped_rel,
path,
target,
(List *) parse->havingQual,
rollup_lists,
rollup_groupclauses,
&agg_costs,
dNumGroups));
}
else if (parse->hasAggs)
{
/*
* We have aggregation, possibly with plain GROUP BY. Make
* an AggPath.
*/
add_path(grouped_rel, (Path *)
create_agg_path(root,
grouped_rel,
path,
target,
parse->groupClause ? AGG_SORTED : AGG_PLAIN,
parse->groupClause,
(List *) parse->havingQual,
&agg_costs,
dNumGroups));
}
else if (parse->groupClause)
{
/*
* We have GROUP BY without aggregation or grouping sets.
* Make a GroupPath.
*/
add_path(grouped_rel, (Path *)
create_group_path(root,
grouped_rel,
path,
target,
parse->groupClause,
(List *) parse->havingQual,
dNumGroups));
}
else
{
/* Other cases should have been handled above */
Assert(false);
}
}
}
}
/*
* Consider hash-based implementations of grouping, if possible.
*
* Hashed aggregation only applies if we're grouping. We currently can't
* hash if there are grouping sets, though.
*
* Executor doesn't support hashed aggregation with DISTINCT or ORDER BY
* aggregates. (Doing so would imply storing *all* the input values in
* the hash table, and/or running many sorts in parallel, either of which
* seems like a certain loser.) We similarly don't support ordered-set
* aggregates in hashed aggregation, but that case is also included in the
* numOrderedAggs count.
*
* Note: grouping_is_hashable() is much more expensive to check than the
* other gating conditions, so we want to do it last.
*/
allow_hash = (parse->groupClause != NIL &&
parse->groupingSets == NIL &&
agg_costs.numOrderedAggs == 0);
/* Consider reasons to disable hashing, but only if we can sort instead */
if (allow_hash && grouped_rel->pathlist != NIL)
{
if (!enable_hashagg)
allow_hash = false;
else
{
/*
* Don't hash if it doesn't look like the hashtable will fit into
* work_mem.
*/
Size hashentrysize;
/* Estimate per-hash-entry space at tuple width... */
hashentrysize = MAXALIGN(cheapest_path->pathtarget->width) +
MAXALIGN(SizeofMinimalTupleHeader);
/* plus space for pass-by-ref transition values... */
hashentrysize += agg_costs.transitionSpace;
/* plus the per-hash-entry overhead */
hashentrysize += hash_agg_entry_size(agg_costs.numAggs);
if (hashentrysize * dNumGroups > work_mem * 1024L)
allow_hash = false;
}
}
if (allow_hash && grouping_is_hashable(parse->groupClause))
{
/*
* We just need an Agg over the cheapest-total input path, since input
* order won't matter.
*/
add_path(grouped_rel, (Path *)
create_agg_path(root, grouped_rel,
cheapest_path,
target,
AGG_HASHED,
parse->groupClause,
(List *) parse->havingQual,
&agg_costs,
dNumGroups));
}
/* Give a helpful error if we failed to find any implementation */
if (grouped_rel->pathlist == NIL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("could not implement GROUP BY"),
errdetail("Some of the datatypes only support hashing, while others only support sorting.")));
/* Now choose the best path(s) */
set_cheapest(grouped_rel);
return grouped_rel;
}
/*
* create_window_paths
*
* Build a new upperrel containing Paths for window-function evaluation.
*
* input_rel: contains the source-data Paths
* input_target: result of make_window_input_target
* output_target: what the topmost WindowAggPath should return
* tlist: query's target list (needed to look up pathkeys)
* wflists: result of find_window_functions
* activeWindows: result of select_active_windows
*
* Note: all Paths in input_rel are expected to return input_target.
*/
static RelOptInfo *
create_window_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *input_target,
PathTarget *output_target,
List *tlist,
WindowFuncLists *wflists,
List *activeWindows)
{
RelOptInfo *window_rel;
ListCell *lc;
/* For now, do all work in the (WINDOW, NULL) upperrel */
window_rel = fetch_upper_rel(root, UPPERREL_WINDOW, NULL);
/*
* Consider computing window functions starting from the existing
* cheapest-total path (which will likely require a sort) as well as any
* existing paths that satisfy root->window_pathkeys (which won't).
*/
foreach(lc, input_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
if (path == input_rel->cheapest_total_path ||
pathkeys_contained_in(root->window_pathkeys, path->pathkeys))
create_one_window_path(root,
window_rel,
path,
input_target,
output_target,
tlist,
wflists,
activeWindows);
}
/* Now choose the best path(s) */
set_cheapest(window_rel);
return window_rel;
}
/*
* Stack window-function implementation steps atop the given Path, and
* add the result to window_rel.
*
* window_rel: upperrel to contain result
* path: input Path to use (must return input_target)
* input_target: result of make_window_input_target
* output_target: what the topmost WindowAggPath should return
* tlist: query's target list (needed to look up pathkeys)
* wflists: result of find_window_functions
* activeWindows: result of select_active_windows
*/
static void
create_one_window_path(PlannerInfo *root,
RelOptInfo *window_rel,
Path *path,
PathTarget *input_target,
PathTarget *output_target,
List *tlist,
WindowFuncLists *wflists,
List *activeWindows)
{
PathTarget *window_target;
ListCell *l;
/*
* Since each window clause could require a different sort order, we stack
* up a WindowAgg node for each clause, with sort steps between them as
* needed. (We assume that select_active_windows chose a good order for
* executing the clauses in.)
*
* input_target should contain all Vars and Aggs needed for the result.
* (In some cases we wouldn't need to propagate all of these all the way
* to the top, since they might only be needed as inputs to WindowFuncs.
* It's probably not worth trying to optimize that though.) It must also
* contain all window partitioning and sorting expressions, to ensure
* they're computed only once at the bottom of the stack (that's critical
* for volatile functions). As we climb up the stack, we'll add outputs
* for the WindowFuncs computed at each level.
*/
window_target = input_target;
foreach(l, activeWindows)
{
WindowClause *wc = (WindowClause *) lfirst(l);
List *window_pathkeys;
window_pathkeys = make_pathkeys_for_window(root,
wc,
tlist);
/* Sort if necessary */
if (!pathkeys_contained_in(window_pathkeys, path->pathkeys))
{
path = (Path *) create_sort_path(root, window_rel,
path,
window_pathkeys,
-1.0);
}
if (lnext(l))
{
/*
* Add the current WindowFuncs to the output target for this
* intermediate WindowAggPath. We must copy window_target to
* avoid changing the previous path's target.
*
* Note: a WindowFunc adds nothing to the target's eval costs; but
* we do need to account for the increase in tlist width.
*/
ListCell *lc2;
window_target = copy_pathtarget(window_target);
foreach(lc2, wflists->windowFuncs[wc->winref])
{
WindowFunc *wfunc = (WindowFunc *) lfirst(lc2);
Assert(IsA(wfunc, WindowFunc));
add_column_to_pathtarget(window_target, (Expr *) wfunc, 0);
window_target->width += get_typavgwidth(wfunc->wintype, -1);
}
}
else
{
/* Install the goal target in the topmost WindowAgg */
window_target = output_target;
}
path = (Path *)
create_windowagg_path(root, window_rel, path, window_target,
wflists->windowFuncs[wc->winref],
wc,
window_pathkeys);
}
add_path(window_rel, path);
}
/*
* create_distinct_paths
*
* Build a new upperrel containing Paths for SELECT DISTINCT evaluation.
*
* input_rel: contains the source-data Paths
*
* Note: input paths should already compute the desired pathtarget, since
* Sort/Unique won't project anything.
*/
static RelOptInfo *
create_distinct_paths(PlannerInfo *root,
RelOptInfo *input_rel)
{
Query *parse = root->parse;
Path *cheapest_input_path = input_rel->cheapest_total_path;
RelOptInfo *distinct_rel;
double numDistinctRows;
bool allow_hash;
Path *path;
ListCell *lc;
/* For now, do all work in the (DISTINCT, NULL) upperrel */
distinct_rel = fetch_upper_rel(root, UPPERREL_DISTINCT, NULL);
/* Estimate number of distinct rows there will be */
if (parse->groupClause || parse->groupingSets || parse->hasAggs ||
root->hasHavingQual)
{
/*
* If there was grouping or aggregation, use the number of input rows
* as the estimated number of DISTINCT rows (ie, assume the input is
* already mostly unique).
*/
numDistinctRows = cheapest_input_path->rows;
}
else
{
/*
* Otherwise, the UNIQUE filter has effects comparable to GROUP BY.
*/
List *distinctExprs;
distinctExprs = get_sortgrouplist_exprs(parse->distinctClause,
parse->targetList);
numDistinctRows = estimate_num_groups(root, distinctExprs,
cheapest_input_path->rows,
NULL);
}
/*
* Consider sort-based implementations of DISTINCT, if possible.
*/
if (grouping_is_sortable(parse->distinctClause))
{
/*
* First, if we have any adequately-presorted paths, just stick a
* Unique node on those. Then consider doing an explicit sort of the
* cheapest input path and Unique'ing that.
*
* When we have DISTINCT ON, we must sort by the more rigorous of
* DISTINCT and ORDER BY, else it won't have the desired behavior.
* Also, if we do have to do an explicit sort, we might as well use
* the more rigorous ordering to avoid a second sort later. (Note
* that the parser will have ensured that one clause is a prefix of
* the other.)
*/
List *needed_pathkeys;
if (parse->hasDistinctOn &&
list_length(root->distinct_pathkeys) <
list_length(root->sort_pathkeys))
needed_pathkeys = root->sort_pathkeys;
else
needed_pathkeys = root->distinct_pathkeys;
foreach(lc, input_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
if (pathkeys_contained_in(needed_pathkeys, path->pathkeys))
{
add_path(distinct_rel, (Path *)
create_upper_unique_path(root, distinct_rel,
path,
list_length(root->distinct_pathkeys),
numDistinctRows));
}
}
/* For explicit-sort case, always use the more rigorous clause */
if (list_length(root->distinct_pathkeys) <
list_length(root->sort_pathkeys))
{
needed_pathkeys = root->sort_pathkeys;
/* Assert checks that parser didn't mess up... */
Assert(pathkeys_contained_in(root->distinct_pathkeys,
needed_pathkeys));
}
else
needed_pathkeys = root->distinct_pathkeys;
path = cheapest_input_path;
if (!pathkeys_contained_in(needed_pathkeys, path->pathkeys))
path = (Path *) create_sort_path(root, distinct_rel,
path,
needed_pathkeys,
-1.0);
add_path(distinct_rel, (Path *)
create_upper_unique_path(root, distinct_rel,
path,
list_length(root->distinct_pathkeys),
numDistinctRows));
}
/*
* Consider hash-based implementations of DISTINCT, if possible.
*
* If we were not able to make any other types of path, we *must* hash or
* die trying. If we do have other choices, there are several things that
* should prevent selection of hashing: if the query uses DISTINCT ON
* (because it won't really have the expected behavior if we hash), or if
* enable_hashagg is off, or if it looks like the hashtable will exceed
* work_mem.
*
* Note: grouping_is_hashable() is much more expensive to check than the
* other gating conditions, so we want to do it last.
*/
if (distinct_rel->pathlist == NIL)
allow_hash = true; /* we have no alternatives */
else if (parse->hasDistinctOn || !enable_hashagg)
allow_hash = false; /* policy-based decision not to hash */
else
{
Size hashentrysize;
/* Estimate per-hash-entry space at tuple width... */
hashentrysize = MAXALIGN(cheapest_input_path->pathtarget->width) +
MAXALIGN(SizeofMinimalTupleHeader);
/* plus the per-hash-entry overhead */
hashentrysize += hash_agg_entry_size(0);
/* Allow hashing only if hashtable is predicted to fit in work_mem */
allow_hash = (hashentrysize * numDistinctRows <= work_mem * 1024L);
}
if (allow_hash && grouping_is_hashable(parse->distinctClause))
{
/* Generate hashed aggregate path --- no sort needed */
add_path(distinct_rel, (Path *)
create_agg_path(root,
distinct_rel,
cheapest_input_path,
cheapest_input_path->pathtarget,
AGG_HASHED,
parse->distinctClause,
NIL,
NULL,
numDistinctRows));
}
/* Give a helpful error if we failed to find any implementation */
if (distinct_rel->pathlist == NIL)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("could not implement DISTINCT"),
errdetail("Some of the datatypes only support hashing, while others only support sorting.")));
/* Now choose the best path(s) */
set_cheapest(distinct_rel);
return distinct_rel;
}
/*
* create_ordered_paths
*
* Build a new upperrel containing Paths for ORDER BY evaluation.
*
* All paths in the result must satisfy the ORDER BY ordering.
* The only new path we need consider is an explicit sort on the
* cheapest-total existing path.
*
* input_rel: contains the source-data Paths
* target: the output tlist the result Paths must emit
* limit_tuples: estimated bound on the number of output tuples,
* or -1 if no LIMIT or couldn't estimate
*/
static RelOptInfo *
create_ordered_paths(PlannerInfo *root,
RelOptInfo *input_rel,
PathTarget *target,
double limit_tuples)
{
Path *cheapest_input_path = input_rel->cheapest_total_path;
RelOptInfo *ordered_rel;
ListCell *lc;
/* For now, do all work in the (ORDERED, NULL) upperrel */
ordered_rel = fetch_upper_rel(root, UPPERREL_ORDERED, NULL);
foreach(lc, input_rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
bool is_sorted;
is_sorted = pathkeys_contained_in(root->sort_pathkeys,
path->pathkeys);
if (path == cheapest_input_path || is_sorted)
{
if (!is_sorted)
{
/* An explicit sort here can take advantage of LIMIT */
path = (Path *) create_sort_path(root,
ordered_rel,
path,
root->sort_pathkeys,
limit_tuples);
}
/* Add projection step if needed */
if (path->pathtarget != target)
path = apply_projection_to_path(root, ordered_rel,
path, target);
add_path(ordered_rel, path);
}
}
/*
* No need to bother with set_cheapest here; grouping_planner does not
* need us to do it.
*/
Assert(ordered_rel->pathlist != NIL);
return ordered_rel;
}
/*
* make_group_input_target
* Generate appropriate PathTarget for initial input to grouping nodes.
*
* If there is grouping or aggregation, the scan/join subplan cannot emit
* the query's final targetlist; for example, it certainly can't emit any
* aggregate function calls. This routine generates the correct target
* for the scan/join subplan.
*
* The query target list passed from the parser already contains entries
* for all ORDER BY and GROUP BY expressions, but it will not have entries
* for variables used only in HAVING clauses; so we need to add those
* variables to the subplan target list. Also, we flatten all expressions
* except GROUP BY items into their component variables; other expressions
* will be computed by the upper plan nodes rather than by the subplan.
* For example, given a query like
* SELECT a+b,SUM(c+d) FROM table GROUP BY a+b;
* we want to pass this targetlist to the subplan:
* a+b,c,d
* where the a+b target will be used by the Sort/Group steps, and the
* other targets will be used for computing the final results.
*
* 'final_target' is the query's final target list (in PathTarget form)
*
* The result is the PathTarget to be computed by the Paths returned from
* query_planner().
*/
static PathTarget *
make_group_input_target(PlannerInfo *root, PathTarget *final_target)
{
Query *parse = root->parse;
PathTarget *input_target;
List *non_group_cols;
List *non_group_vars;
int i;
ListCell *lc;
/*
* We must build a target containing all grouping columns, plus any other
* Vars mentioned in the query's targetlist and HAVING qual.
*/
input_target = create_empty_pathtarget();
non_group_cols = NIL;
i = 0;
foreach(lc, final_target->exprs)
{
Expr *expr = (Expr *) lfirst(lc);
Index sgref = final_target->sortgrouprefs[i];
if (sgref && parse->groupClause &&
get_sortgroupref_clause_noerr(sgref, parse->groupClause) != NULL)
{
/*
* It's a grouping column, so add it to the input target as-is.
*/
add_column_to_pathtarget(input_target, expr, sgref);
}
else
{
/*
* Non-grouping column, so just remember the expression for later
* call to pull_var_clause.
*/
non_group_cols = lappend(non_group_cols, expr);
}
i++;
}
/*
* If there's a HAVING clause, we'll need the Vars it uses, too.
*/
if (parse->havingQual)
non_group_cols = lappend(non_group_cols, parse->havingQual);
/*
* Pull out all the Vars mentioned in non-group cols (plus HAVING), and
* add them to the input target if not already present. (A Var used
* directly as a GROUP BY item will be present already.) Note this
* includes Vars used in resjunk items, so we are covering the needs of
* ORDER BY and window specifications. Vars used within Aggrefs and
* WindowFuncs will be pulled out here, too.
*/
non_group_vars = pull_var_clause((Node *) non_group_cols,
PVC_RECURSE_AGGREGATES |
PVC_RECURSE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
add_new_columns_to_pathtarget(input_target, non_group_vars);
/* clean up cruft */
list_free(non_group_vars);
list_free(non_group_cols);
/* XXX this causes some redundant cost calculation ... */
return set_pathtarget_cost_width(root, input_target);
}
/*
* postprocess_setop_tlist
* Fix up targetlist returned by plan_set_operations().
*
* We need to transpose sort key info from the orig_tlist into new_tlist.
* NOTE: this would not be good enough if we supported resjunk sort keys
* for results of set operations --- then, we'd need to project a whole
* new tlist to evaluate the resjunk columns. For now, just ereport if we
* find any resjunk columns in orig_tlist.
*/
static List *
postprocess_setop_tlist(List *new_tlist, List *orig_tlist)
{
ListCell *l;
ListCell *orig_tlist_item = list_head(orig_tlist);
foreach(l, new_tlist)
{
TargetEntry *new_tle = (TargetEntry *) lfirst(l);
TargetEntry *orig_tle;
/* ignore resjunk columns in setop result */
if (new_tle->resjunk)
continue;
Assert(orig_tlist_item != NULL);
orig_tle = (TargetEntry *) lfirst(orig_tlist_item);
orig_tlist_item = lnext(orig_tlist_item);
if (orig_tle->resjunk) /* should not happen */
elog(ERROR, "resjunk output columns are not implemented");
Assert(new_tle->resno == orig_tle->resno);
new_tle->ressortgroupref = orig_tle->ressortgroupref;
}
if (orig_tlist_item != NULL)
elog(ERROR, "resjunk output columns are not implemented");
return new_tlist;
}
/*
* select_active_windows
* Create a list of the "active" window clauses (ie, those referenced
* by non-deleted WindowFuncs) in the order they are to be executed.
*/
static List *
select_active_windows(PlannerInfo *root, WindowFuncLists *wflists)
{
List *result;
List *actives;
ListCell *lc;
/* First, make a list of the active windows */
actives = NIL;
foreach(lc, root->parse->windowClause)
{
WindowClause *wc = (WindowClause *) lfirst(lc);
/* It's only active if wflists shows some related WindowFuncs */
Assert(wc->winref <= wflists->maxWinRef);
if (wflists->windowFuncs[wc->winref] != NIL)
actives = lappend(actives, wc);
}
/*
* Now, ensure that windows with identical partitioning/ordering clauses
* are adjacent in the list. This is required by the SQL standard, which
* says that only one sort is to be used for such windows, even if they
* are otherwise distinct (eg, different names or framing clauses).
*
* There is room to be much smarter here, for example detecting whether
* one window's sort keys are a prefix of another's (so that sorting for
* the latter would do for the former), or putting windows first that
* match a sort order available for the underlying query. For the moment
* we are content with meeting the spec.
*/
result = NIL;
while (actives != NIL)
{
WindowClause *wc = (WindowClause *) linitial(actives);
ListCell *prev;
ListCell *next;
/* Move wc from actives to result */
actives = list_delete_first(actives);
result = lappend(result, wc);
/* Now move any matching windows from actives to result */
prev = NULL;
for (lc = list_head(actives); lc; lc = next)
{
WindowClause *wc2 = (WindowClause *) lfirst(lc);
next = lnext(lc);
/* framing options are NOT to be compared here! */
if (equal(wc->partitionClause, wc2->partitionClause) &&
equal(wc->orderClause, wc2->orderClause))
{
actives = list_delete_cell(actives, lc, prev);
result = lappend(result, wc2);
}
else
prev = lc;
}
}
return result;
}
/*
* make_window_input_target
* Generate appropriate PathTarget for initial input to WindowAgg nodes.
*
* When the query has window functions, this function computes the desired
* target to be computed by the node just below the first WindowAgg.
* This tlist must contain all values needed to evaluate the window functions,
* compute the final target list, and perform any required final sort step.
* If multiple WindowAggs are needed, each intermediate one adds its window
* function results onto this base tlist; only the topmost WindowAgg computes
* the actual desired target list.
*
* This function is much like make_group_input_target, though not quite enough
* like it to share code. As in that function, we flatten most expressions
* into their component variables. But we do not want to flatten window
* PARTITION BY/ORDER BY clauses, since that might result in multiple
* evaluations of them, which would be bad (possibly even resulting in
* inconsistent answers, if they contain volatile functions).
* Also, we must not flatten GROUP BY clauses that were left unflattened by
* make_group_input_target, because we may no longer have access to the
* individual Vars in them.
*
* Another key difference from make_group_input_target is that we don't
* flatten Aggref expressions, since those are to be computed below the
* window functions and just referenced like Vars above that.
*
* 'final_target' is the query's final target list (in PathTarget form)
* 'activeWindows' is the list of active windows previously identified by
* select_active_windows.
*
* The result is the PathTarget to be computed by the plan node immediately
* below the first WindowAgg node.
*/
static PathTarget *
make_window_input_target(PlannerInfo *root,
PathTarget *final_target,
List *activeWindows)
{
Query *parse = root->parse;
PathTarget *input_target;
Bitmapset *sgrefs;
List *flattenable_cols;
List *flattenable_vars;
int i;
ListCell *lc;
Assert(parse->hasWindowFuncs);
/*
* Collect the sortgroupref numbers of window PARTITION/ORDER BY clauses
* into a bitmapset for convenient reference below.
*/
sgrefs = NULL;
foreach(lc, activeWindows)
{
WindowClause *wc = (WindowClause *) lfirst(lc);
ListCell *lc2;
foreach(lc2, wc->partitionClause)
{
SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc2);
sgrefs = bms_add_member(sgrefs, sortcl->tleSortGroupRef);
}
foreach(lc2, wc->orderClause)
{
SortGroupClause *sortcl = (SortGroupClause *) lfirst(lc2);
sgrefs = bms_add_member(sgrefs, sortcl->tleSortGroupRef);
}
}
/* Add in sortgroupref numbers of GROUP BY clauses, too */
foreach(lc, parse->groupClause)
{
SortGroupClause *grpcl = (SortGroupClause *) lfirst(lc);
sgrefs = bms_add_member(sgrefs, grpcl->tleSortGroupRef);
}
/*
* Construct a target containing all the non-flattenable targetlist items,
* and save aside the others for a moment.
*/
input_target = create_empty_pathtarget();
flattenable_cols = NIL;
i = 0;
foreach(lc, final_target->exprs)
{
Expr *expr = (Expr *) lfirst(lc);
Index sgref = final_target->sortgrouprefs[i];
/*
* Don't want to deconstruct window clauses or GROUP BY items. (Note
* that such items can't contain window functions, so it's okay to
* compute them below the WindowAgg nodes.)
*/
if (sgref != 0 && bms_is_member(sgref, sgrefs))
{
/*
* Don't want to deconstruct this value, so add it to the input
* target as-is.
*/
add_column_to_pathtarget(input_target, expr, sgref);
}
else
{
/*
* Column is to be flattened, so just remember the expression for
* later call to pull_var_clause.
*/
flattenable_cols = lappend(flattenable_cols, expr);
}
i++;
}
/*
* Pull out all the Vars and Aggrefs mentioned in flattenable columns, and
* add them to the input target if not already present. (Some might be
* there already because they're used directly as window/group clauses.)
*
* Note: it's essential to use PVC_INCLUDE_AGGREGATES here, so that any
* Aggrefs are placed in the Agg node's tlist and not left to be computed
* at higher levels. On the other hand, we should recurse into
* WindowFuncs to make sure their input expressions are available.
*/
flattenable_vars = pull_var_clause((Node *) flattenable_cols,
PVC_INCLUDE_AGGREGATES |
PVC_RECURSE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
add_new_columns_to_pathtarget(input_target, flattenable_vars);
/* clean up cruft */
list_free(flattenable_vars);
list_free(flattenable_cols);
/* XXX this causes some redundant cost calculation ... */
return set_pathtarget_cost_width(root, input_target);
}
/*
* make_pathkeys_for_window
* Create a pathkeys list describing the required input ordering
* for the given WindowClause.
*
* The required ordering is first the PARTITION keys, then the ORDER keys.
* In the future we might try to implement windowing using hashing, in which
* case the ordering could be relaxed, but for now we always sort.
*
* Caution: if you change this, see createplan.c's get_column_info_for_window!
*/
static List *
make_pathkeys_for_window(PlannerInfo *root, WindowClause *wc,
List *tlist)
{
List *window_pathkeys;
List *window_sortclauses;
/* Throw error if can't sort */
if (!grouping_is_sortable(wc->partitionClause))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("could not implement window PARTITION BY"),
errdetail("Window partitioning columns must be of sortable datatypes.")));
if (!grouping_is_sortable(wc->orderClause))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("could not implement window ORDER BY"),
errdetail("Window ordering columns must be of sortable datatypes.")));
/* Okay, make the combined pathkeys */
window_sortclauses = list_concat(list_copy(wc->partitionClause),
list_copy(wc->orderClause));
window_pathkeys = make_pathkeys_for_sortclauses(root,
window_sortclauses,
tlist);
list_free(window_sortclauses);
return window_pathkeys;
}
/*
* make_sort_input_target
* Generate appropriate PathTarget for initial input to Sort step.
*
* If the query has ORDER BY, this function chooses the target to be computed
* by the node just below the Sort (and DISTINCT, if any, since Unique can't
* project) steps. This might or might not be identical to the query's final
* output target.
*
* The main argument for keeping the sort-input tlist the same as the final
* is that we avoid a separate projection node (which will be needed if
* they're different, because Sort can't project). However, there are also
* advantages to postponing tlist evaluation till after the Sort: it ensures
* a consistent order of evaluation for any volatile functions in the tlist,
* and if there's also a LIMIT, we can stop the query without ever computing
* tlist functions for later rows, which is beneficial for both volatile and
* expensive functions.
*
* Our current policy is to postpone volatile expressions till after the sort
* unconditionally (assuming that that's possible, ie they are in plain tlist
* columns and not ORDER BY/GROUP BY/DISTINCT columns). We also postpone
* set-returning expressions unconditionally (if possible), because running
* them beforehand would bloat the sort dataset, and because it might cause
* unexpected output order if the sort isn't stable. Expensive expressions
* are postponed if there is a LIMIT, or if root->tuple_fraction shows that
* partial evaluation of the query is possible (if neither is true, we expect
* to have to evaluate the expressions for every row anyway), or if there are
* any volatile or set-returning expressions (since once we've put in a
* projection at all, it won't cost any more to postpone more stuff).
*
* Another issue that could potentially be considered here is that
* evaluating tlist expressions could result in data that's either wider
* or narrower than the input Vars, thus changing the volume of data that
* has to go through the Sort. However, we usually have only a very bad
* idea of the output width of any expression more complex than a Var,
* so for now it seems too risky to try to optimize on that basis.
*
* Note that if we do produce a modified sort-input target, and then the
* query ends up not using an explicit Sort, no particular harm is done:
* we'll initially use the modified target for the preceding path nodes,
* but then change them to the final target with apply_projection_to_path.
* Moreover, in such a case the guarantees about evaluation order of
* volatile functions still hold, since the rows are sorted already.
*
* This function has some things in common with make_group_input_target and
* make_window_input_target, though the detailed rules for what to do are
* different. We never flatten/postpone any grouping or ordering columns;
* those are needed before the sort. If we do flatten a particular
* expression, we leave Aggref and WindowFunc nodes alone, since those were
* computed earlier.
*
* 'final_target' is the query's final target list (in PathTarget form)
* 'have_postponed_srfs' is an output argument, see below
*
* The result is the PathTarget to be computed by the plan node immediately
* below the Sort step (and the Distinct step, if any). This will be
* exactly final_target if we decide a projection step wouldn't be helpful.
*
* In addition, *have_postponed_srfs is set to TRUE if we choose to postpone
* any set-returning functions to after the Sort.
*/
static PathTarget *
make_sort_input_target(PlannerInfo *root,
PathTarget *final_target,
bool *have_postponed_srfs)
{
Query *parse = root->parse;
PathTarget *input_target;
int ncols;
bool *postpone_col;
bool have_srf;
bool have_volatile;
bool have_expensive;
List *postponable_cols;
List *postponable_vars;
int i;
ListCell *lc;
/* Shouldn't get here unless query has ORDER BY */
Assert(parse->sortClause);
*have_postponed_srfs = false; /* default result */
/* Inspect tlist and collect per-column information */
ncols = list_length(final_target->exprs);
postpone_col = (bool *) palloc0(ncols * sizeof(bool));
have_srf = have_volatile = have_expensive = false;
i = 0;
foreach(lc, final_target->exprs)
{
Expr *expr = (Expr *) lfirst(lc);
/*
* If the column has a sortgroupref, assume it has to be evaluated
* before sorting. Generally such columns would be ORDER BY, GROUP
* BY, etc targets. One exception is columns that were removed from
* GROUP BY by remove_useless_groupby_columns() ... but those would
* only be Vars anyway. There don't seem to be any cases where it
* would be worth the trouble to double-check.
*/
if (final_target->sortgrouprefs[i] == 0)
{
/*
* If it returns a set or is volatile, that's an unconditional
* reason to postpone. Check the SRF case first because we must
* know whether we have any postponed SRFs.
*/
if (expression_returns_set((Node *) expr))
{
postpone_col[i] = true;
have_srf = true;
}
else if (contain_volatile_functions((Node *) expr))
{
postpone_col[i] = true;
have_volatile = true;
}
else
{
/*
* Else check the cost. XXX it's annoying to have to do this
* when set_pathtarget_cost_width() just did it. Refactor to
* allow sharing the work?
*/
QualCost cost;
cost_qual_eval_node(&cost, (Node *) expr, root);
/*
* We arbitrarily define "expensive" as "more than 10X
* cpu_operator_cost". Note this will take in any PL function
* with default cost.
*/
if (cost.per_tuple > 10 * cpu_operator_cost)
{
postpone_col[i] = true;
have_expensive = true;
}
}
}
i++;
}
/*
* If we don't need a post-sort projection, just return final_target.
*/
if (!(have_srf || have_volatile ||
(have_expensive &&
(parse->limitCount || root->tuple_fraction > 0))))
return final_target;
/*
* Report whether the post-sort projection will contain set-returning
* functions. This is important because it affects whether the Sort can
* rely on the query's LIMIT (if any) to bound the number of rows it needs
* to return.
*/
*have_postponed_srfs = have_srf;
/*
* Construct the sort-input target, taking all non-postponable columns and
* then adding Vars, PlaceHolderVars, Aggrefs, and WindowFuncs found in
* the postponable ones.
*/
input_target = create_empty_pathtarget();
postponable_cols = NIL;
i = 0;
foreach(lc, final_target->exprs)
{
Expr *expr = (Expr *) lfirst(lc);
if (postpone_col[i])
postponable_cols = lappend(postponable_cols, expr);
else
add_column_to_pathtarget(input_target, expr,
final_target->sortgrouprefs[i]);
i++;
}
/*
* Pull out all the Vars, Aggrefs, and WindowFuncs mentioned in
* postponable columns, and add them to the sort-input target if not
* already present. (Some might be there already.) We mustn't
* deconstruct Aggrefs or WindowFuncs here, since the projection node
* would be unable to recompute them.
*/
postponable_vars = pull_var_clause((Node *) postponable_cols,
PVC_INCLUDE_AGGREGATES |
PVC_INCLUDE_WINDOWFUNCS |
PVC_INCLUDE_PLACEHOLDERS);
add_new_columns_to_pathtarget(input_target, postponable_vars);
/* clean up cruft */
list_free(postponable_vars);
list_free(postponable_cols);
/* XXX this represents even more redundant cost calculation ... */
return set_pathtarget_cost_width(root, input_target);
}
/*
* get_cheapest_fractional_path
* Find the cheapest path for retrieving a specified fraction of all
* the tuples expected to be returned by the given relation.
*
* We interpret tuple_fraction the same way as grouping_planner.
*
* We assume set_cheapest() has been run on the given rel.
*/
Path *
get_cheapest_fractional_path(RelOptInfo *rel, double tuple_fraction)
{
Path *best_path = rel->cheapest_total_path;
ListCell *l;
/* If all tuples will be retrieved, just return the cheapest-total path */
if (tuple_fraction <= 0.0)
return best_path;
/* Convert absolute # of tuples to a fraction; no need to clamp */
if (tuple_fraction >= 1.0)
tuple_fraction /= best_path->rows;
foreach(l, rel->pathlist)
{
Path *path = (Path *) lfirst(l);
if (path == rel->cheapest_total_path ||
compare_fractional_path_costs(best_path, path, tuple_fraction) <= 0)
continue;
best_path = path;
}
return best_path;
}
/*
* expression_planner
* Perform planner's transformations on a standalone expression.
*
* Various utility commands need to evaluate expressions that are not part
* of a plannable query. They can do so using the executor's regular
* expression-execution machinery, but first the expression has to be fed
* through here to transform it from parser output to something executable.
*
* Currently, we disallow sublinks in standalone expressions, so there's no
* real "planning" involved here. (That might not always be true though.)
* What we must do is run eval_const_expressions to ensure that any function
* calls are converted to positional notation and function default arguments
* get inserted. The fact that constant subexpressions get simplified is a
* side-effect that is useful when the expression will get evaluated more than
* once. Also, we must fix operator function IDs.
*
* Note: this must not make any damaging changes to the passed-in expression
* tree. (It would actually be okay to apply fix_opfuncids to it, but since
* we first do an expression_tree_mutator-based walk, what is returned will
* be a new node tree.)
*/
Expr *
expression_planner(Expr *expr)
{
Node *result;
/*
* Convert named-argument function calls, insert default arguments and
* simplify constant subexprs
*/
result = eval_const_expressions(NULL, (Node *) expr);
/* Fill in opfuncid values if missing */
fix_opfuncids(result);
return (Expr *) result;
}
/*
* plan_cluster_use_sort
* Use the planner to decide how CLUSTER should implement sorting
*
* tableOid is the OID of a table to be clustered on its index indexOid
* (which is already known to be a btree index). Decide whether it's
* cheaper to do an indexscan or a seqscan-plus-sort to execute the CLUSTER.
* Return TRUE to use sorting, FALSE to use an indexscan.
*
* Note: caller had better already hold some type of lock on the table.
*/
bool
plan_cluster_use_sort(Oid tableOid, Oid indexOid)
{
PlannerInfo *root;
Query *query;
PlannerGlobal *glob;
RangeTblEntry *rte;
RelOptInfo *rel;
IndexOptInfo *indexInfo;
QualCost indexExprCost;
Cost comparisonCost;
Path *seqScanPath;
Path seqScanAndSortPath;
IndexPath *indexScanPath;
ListCell *lc;
/* Set up mostly-dummy planner state */
query = makeNode(Query);
query->commandType = CMD_SELECT;
glob = makeNode(PlannerGlobal);
root = makeNode(PlannerInfo);
root->parse = query;
root->glob = glob;
root->query_level = 1;
root->planner_cxt = CurrentMemoryContext;
root->wt_param_id = -1;
/* Build a minimal RTE for the rel */
rte = makeNode(RangeTblEntry);
rte->rtekind = RTE_RELATION;
rte->relid = tableOid;
rte->relkind = RELKIND_RELATION; /* Don't be too picky. */
rte->lateral = false;
rte->inh = false;
rte->inFromCl = true;
query->rtable = list_make1(rte);
/* Set up RTE/RelOptInfo arrays */
setup_simple_rel_arrays(root);
/* Build RelOptInfo */
rel = build_simple_rel(root, 1, RELOPT_BASEREL);
/* Locate IndexOptInfo for the target index */
indexInfo = NULL;
foreach(lc, rel->indexlist)
{
indexInfo = (IndexOptInfo *) lfirst(lc);
if (indexInfo->indexoid == indexOid)
break;
}
/*
* It's possible that get_relation_info did not generate an IndexOptInfo
* for the desired index; this could happen if it's not yet reached its
* indcheckxmin usability horizon, or if it's a system index and we're
* ignoring system indexes. In such cases we should tell CLUSTER to not
* trust the index contents but use seqscan-and-sort.
*/
if (lc == NULL) /* not in the list? */
return true; /* use sort */
/*
* Rather than doing all the pushups that would be needed to use
* set_baserel_size_estimates, just do a quick hack for rows and width.
*/
rel->rows = rel->tuples;
rel->reltarget->width = get_relation_data_width(tableOid, NULL);
root->total_table_pages = rel->pages;
/*
* Determine eval cost of the index expressions, if any. We need to
* charge twice that amount for each tuple comparison that happens during
* the sort, since tuplesort.c will have to re-evaluate the index
* expressions each time. (XXX that's pretty inefficient...)
*/
cost_qual_eval(&indexExprCost, indexInfo->indexprs, root);
comparisonCost = 2.0 * (indexExprCost.startup + indexExprCost.per_tuple);
/* Estimate the cost of seq scan + sort */
seqScanPath = create_seqscan_path(root, rel, NULL, 0);
cost_sort(&seqScanAndSortPath, root, NIL,
seqScanPath->total_cost, rel->tuples, rel->reltarget->width,
comparisonCost, maintenance_work_mem, -1.0);
/* Estimate the cost of index scan */
indexScanPath = create_index_path(root, indexInfo,
NIL, NIL, NIL, NIL, NIL,
ForwardScanDirection, false,
NULL, 1.0);
return (seqScanAndSortPath.total_cost < indexScanPath->path.total_cost);
}
View Git Blame Copy Permalink