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postgres/src/backend/optimizer/plan/planner.c
Tom Lane 784e762e88 Support multi-argument UNNEST(), and TABLE() syntax for multiple functions. 
This patch adds the ability to write TABLE( function1(), function2(), ...)
as a single FROM-clause entry.  The result is the concatenation of the
first row from each function, followed by the second row from each
function, etc; with NULLs inserted if any function produces fewer rows than
others.  This is believed to be a much more useful behavior than what
Postgres currently does with multiple SRFs in a SELECT list.

This syntax also provides a reasonable way to combine use of column
definition lists with WITH ORDINALITY: put the column definition list
inside TABLE(), where it's clear that it doesn't control the ordinality
column as well.

Also implement SQL-compliant multiple-argument UNNEST(), by turning
UNNEST(a,b,c) into TABLE(unnest(a), unnest(b), unnest(c)).

The SQL standard specifies TABLE() with only a single function, not
multiple functions, and it seems to require an implicit UNNEST() which is
not what this patch does.  There may be something wrong with that reading
of the spec, though, because if it's right then the spec's TABLE() is just
a pointless alternative spelling of UNNEST().  After further review of
that, we might choose to adopt a different syntax for what this patch does,
but in any case this functionality seems clearly worthwhile.

Andrew Gierth, reviewed by Zoltán Böszörményi and Heikki Linnakangas, and
significantly revised by me
2013-11-21 19:37:20 -05:00

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/*-------------------------------------------------------------------------
*
* planner.c
* The query optimizer external interface.
*
* Portions Copyright (c) 1996-2013, 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 "access/htup_details.h"
#include "executor/executor.h"
#include "executor/nodeAgg.h"
#include "miscadmin.h"
#include "nodes/makefuncs.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 "parser/analyze.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteManip.h"
#include "utils/rel.h"
#include "utils/selfuncs.h"
/* GUC parameter */
double cursor_tuple_fraction = DEFAULT_CURSOR_TUPLE_FRACTION;
/* Hook for plugins to get control in planner() */
planner_hook_type planner_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
/* Passthrough data for standard_qp_callback */
typedef struct
{
List *tlist; /* preprocessed query targetlist */
List *activeWindows; /* active windows, if any */
} 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 Plan *inheritance_planner(PlannerInfo *root);
static Plan *grouping_planner(PlannerInfo *root, 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 preprocess_groupclause(PlannerInfo *root);
static void standard_qp_callback(PlannerInfo *root, void *extra);
static bool choose_hashed_grouping(PlannerInfo *root,
double tuple_fraction, double limit_tuples,
double path_rows, int path_width,
Path *cheapest_path, Path *sorted_path,
double dNumGroups, AggClauseCosts *agg_costs);
static bool choose_hashed_distinct(PlannerInfo *root,
double tuple_fraction, double limit_tuples,
double path_rows, int path_width,
Cost cheapest_startup_cost, Cost cheapest_total_cost,
Cost sorted_startup_cost, Cost sorted_total_cost,
List *sorted_pathkeys,
double dNumDistinctRows);
static List *make_subplanTargetList(PlannerInfo *root, List *tlist,
AttrNumber **groupColIdx, bool *need_tlist_eval);
static int get_grouping_column_index(Query *parse, TargetEntry *tle);
static void locate_grouping_columns(PlannerInfo *root,
List *tlist,
List *sub_tlist,
AttrNumber *groupColIdx);
static List *postprocess_setop_tlist(List *new_tlist, List *orig_tlist);
static List *select_active_windows(PlannerInfo *root, WindowFuncLists *wflists);
static List *make_windowInputTargetList(PlannerInfo *root,
List *tlist, List *activeWindows);
static List *make_pathkeys_for_window(PlannerInfo *root, WindowClause *wc,
List *tlist);
static void get_column_info_for_window(PlannerInfo *root, WindowClause *wc,
List *tlist,
int numSortCols, AttrNumber *sortColIdx,
int *partNumCols,
AttrNumber **partColIdx,
Oid **partOperators,
int *ordNumCols,
AttrNumber **ordColIdx,
Oid **ordOperators);
/*****************************************************************************
*
* 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;
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->transientPlan = 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) */
top_plan = subquery_planner(glob, parse, NULL,
false, tuple_fraction, &root);
/*
* 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);
}
/* 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;
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.
*
* If subroot isn't NULL, we pass back the query's final PlannerInfo struct;
* among other things this tells the output sort ordering of the plan.
*
* 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 a query plan.
*--------------------
*/
Plan *
subquery_planner(PlannerGlobal *glob, Query *parse,
PlannerInfo *parent_root,
bool hasRecursion, double tuple_fraction,
PlannerInfo **subroot)
{
int num_old_subplans = list_length(glob->subplans);
PlannerInfo *root;
Plan *plan;
List *newWithCheckOptions;
List *newHaving;
bool hasOuterJoins;
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->planner_cxt = CurrentMemoryContext;
root->init_plans = NIL;
root->cte_plan_ids = NIL;
root->eq_classes = NIL;
root->append_rel_list = NIL;
root->rowMarks = 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_plan = 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.
*/
parse->jointree = (FromExpr *)
pull_up_subqueries(root, (Node *) parse->jointree);
/*
* 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);
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_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). 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 (contain_agg_clause(havingclause) ||
contain_volatile_functions(havingclause) ||
contain_subplans(havingclause))
{
/* keep it in HAVING */
newHaving = lappend(newHaving, havingclause);
}
else if (parse->groupClause)
{
/* 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;
/*
* 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)
plan = inheritance_planner(root);
else
{
plan = grouping_planner(root, tuple_fraction);
/* If it's not SELECT, we need a ModifyTable node */
if (parse->commandType != CMD_SELECT)
{
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;
plan = (Plan *) make_modifytable(root,
parse->commandType,
parse->canSetTag,
list_make1_int(parse->resultRelation),
list_make1(plan),
withCheckOptionLists,
returningLists,
rowMarks,
SS_assign_special_param(root));
}
}
/*
* If any subplans were generated, or if there are any parameters to worry
* about, build initPlan list and extParam/allParam sets for plan nodes,
* and attach the initPlans to the top plan node.
*/
if (list_length(glob->subplans) != num_old_subplans ||
root->glob->nParamExec > 0)
SS_finalize_plan(root, plan, true);
/* Return internal info if caller wants it */
if (subroot)
*subroot = root;
return plan;
}
/*
* 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 and VALUES lists, however,
* since they can't contain any Vars of the current query level.
*/
if (root->hasJoinRTEs &&
!(kind == EXPRKIND_RTFUNC || kind == EXPRKIND_VALUES))
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 a plan 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 a query plan.
*/
static Plan *
inheritance_planner(PlannerInfo *root)
{
Query *parse = root->parse;
int parentRTindex = parse->resultRelation;
List *final_rtable = NIL;
int save_rel_array_size = 0;
RelOptInfo **save_rel_array = NULL;
List *subplans = NIL;
List *resultRelations = NIL;
List *withCheckOptionLists = NIL;
List *returningLists = NIL;
List *rowMarks;
ListCell *lc;
/*
* 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.
*/
foreach(lc, root->append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
PlannerInfo subroot;
Plan *subplan;
Index rti;
/* 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.
*/
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);
/*
* 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 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)
{
ListCell *lr;
rti = 1;
foreach(lr, parse->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lr);
if (rte->rtekind == RTE_SUBQUERY)
{
Index newrti;
/*
* The RTE can't contain any references to its own RT
* index, 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);
rte = copyObject(rte);
subroot.parse->rtable = lappend(subroot.parse->rtable,
rte);
}
rti++;
}
}
/* We needn't modify the child's append_rel_list */
/* There shouldn't be any OJ or LATERAL info to translate, as yet */
Assert(subroot.join_info_list == NIL);
Assert(subroot.lateral_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 plan */
subplan = grouping_planner(&subroot, 0.0 /* retrieve all tuples */ );
/*
* If this child rel was excluded by constraint exclusion, exclude it
* from the result plan.
*/
if (is_dummy_plan(subplan))
continue;
subplans = lappend(subplans, subplan);
/*
* 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
final_rtable = list_concat(final_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 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);
}
/* Mark result as unordered (probably unnecessary) */
root->query_pathkeys = NIL;
/*
* If we managed to exclude every child rel, return a dummy plan; it
* doesn't even need a ModifyTable node.
*/
if (subplans == NIL)
{
/* although dummy, it must have a valid tlist for executor */
List *tlist;
tlist = preprocess_targetlist(root, parse->targetList);
return (Plan *) make_result(root,
tlist,
(Node *) list_make1(makeBoolConst(false,
false)),
NULL);
}
/*
* Put back the final adjusted rtable into the master copy of the Query.
*/
parse->rtable = final_rtable;
root->simple_rel_array_size = save_rel_array_size;
root->simple_rel_array = save_rel_array;
/*
* 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;
/* And last, tack on a ModifyTable node to do the UPDATE/DELETE work */
return (Plan *) make_modifytable(root,
parse->commandType,
parse->canSetTag,
resultRelations,
subplans,
withCheckOptionLists,
returningLists,
rowMarks,
SS_assign_special_param(root));
}
/*--------------------
* grouping_planner
* Perform planning steps related to grouping, aggregation, etc.
* This primarily means adding top-level processing to the basic
* query plan produced by query_planner.
*
* 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 a query plan. Also, root->query_pathkeys is returned as the
* actual output ordering of the plan (in pathkey format).
*--------------------
*/
static Plan *
grouping_planner(PlannerInfo *root, double tuple_fraction)
{
Query *parse = root->parse;
List *tlist = parse->targetList;
int64 offset_est = 0;
int64 count_est = 0;
double limit_tuples = -1.0;
Plan *result_plan;
List *current_pathkeys;
double dNumGroups = 0;
bool use_hashed_distinct = false;
bool tested_hashed_distinct = false;
/* 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;
}
if (parse->setOperations)
{
List *set_sortclauses;
/*
* 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.
*/
if (parse->sortClause)
tuple_fraction = 0.0;
/*
* Construct the plan for set operations. The result 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.
*/
result_plan = plan_set_operations(root, tuple_fraction,
&set_sortclauses);
/*
* Calculate pathkeys representing the sort order (if any) of the set
* operation's result. We have to do this before overwriting the sort
* key information...
*/
current_pathkeys = make_pathkeys_for_sortclauses(root,
set_sortclauses,
result_plan->targetlist);
/*
* 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 = postprocess_setop_tlist(copyObject(result_plan->targetlist),
tlist);
/*
* 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 */
List *sub_tlist;
AttrNumber *groupColIdx = NULL;
bool need_tlist_eval = true;
standard_qp_extra qp_extra;
RelOptInfo *final_rel;
Path *cheapest_path;
Path *sorted_path;
Path *best_path;
long numGroups = 0;
AggClauseCosts agg_costs;
int numGroupCols;
double path_rows;
int path_width;
bool use_hashed_grouping = false;
WindowFuncLists *wflists = NULL;
List *activeWindows = NIL;
MemSet(&agg_costs, 0, sizeof(AggClauseCosts));
/* A recursive query should always have setOperations */
Assert(!root->hasRecursion);
/* Preprocess GROUP BY clause, if any */
if (parse->groupClause)
preprocess_groupclause(root);
numGroupCols = list_length(parse->groupClause);
/* Preprocess targetlist */
tlist = preprocess_targetlist(root, 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;
}
/*
* Generate appropriate target list for subplan; may be different from
* tlist if grouping or aggregation is needed.
*/
sub_tlist = make_subplanTargetList(root, tlist,
&groupColIdx, &need_tlist_eval);
/*
* Do aggregate preprocessing, if the query has any aggs.
*
* Note: think not that we can turn off hasAggs if we find no aggs. It
* is possible for constant-expression simplification to remove all
* explicit references to aggs, but we still have to follow the
* aggregate semantics (eg, producing only one output row).
*/
if (parse->hasAggs)
{
/*
* Collect statistics about aggregates for estimating costs. Note:
* we do not attempt to detect duplicate aggregates here; a
* somewhat-overestimated cost is okay for our present purposes.
*/
count_agg_clauses(root, (Node *) tlist, &agg_costs);
count_agg_clauses(root, parse->havingQual, &agg_costs);
/*
* Preprocess MIN/MAX aggregates, if any. Note: be careful about
* adding logic between here and the optimize_minmax_aggregates
* call. Anything that is needed in MIN/MAX-optimizable cases
* will have to be duplicated in planagg.c.
*/
preprocess_minmax_aggregates(root, tlist);
}
/* Make tuple_fraction accessible to lower-level routines */
root->tuple_fraction = tuple_fraction;
/*
* 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.
*/
if (parse->groupClause ||
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;
/*
* Generate the best unsorted and presorted paths for this Query (but
* 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.
*/
final_rel = query_planner(root, sub_tlist,
standard_qp_callback, &qp_extra);
/*
* Extract rowcount and width estimates for use below.
*/
path_rows = final_rel->rows;
path_width = final_rel->width;
/*
* If there's grouping going on, estimate the number of result groups.
* We couldn't do this any earlier because it depends on relation size
* estimates that are created within query_planner().
*
* Then convert tuple_fraction to fractional form if it is absolute,
* and if grouping or aggregation is involved, adjust tuple_fraction
* to describe the fraction of the underlying un-aggregated tuples
* that will be fetched.
*/
dNumGroups = 1; /* in case not grouping */
if (parse->groupClause)
{
List *groupExprs;
groupExprs = get_sortgrouplist_exprs(parse->groupClause,
parse->targetList);
dNumGroups = estimate_num_groups(root, groupExprs, path_rows);
/*
* In GROUP BY mode, an absolute LIMIT is relative to the number
* of groups not the number of tuples. If the caller gave us a
* fraction, keep it as-is. (In both cases, we are effectively
* assuming that all the groups are about the same size.)
*/
if (tuple_fraction >= 1.0)
tuple_fraction /= dNumGroups;
/*
* If both GROUP BY and ORDER BY are specified, we will need two
* levels of sort --- and, therefore, certainly need to read all
* the tuples --- unless ORDER BY is a subset of GROUP BY.
* Likewise if we have both DISTINCT and GROUP BY, or if we have a
* window specification not compatible with the GROUP BY.
*/
if (!pathkeys_contained_in(root->sort_pathkeys,
root->group_pathkeys) ||
!pathkeys_contained_in(root->distinct_pathkeys,
root->group_pathkeys) ||
!pathkeys_contained_in(root->window_pathkeys,
root->group_pathkeys))
tuple_fraction = 0.0;
}
else if (parse->hasAggs || root->hasHavingQual)
{
/*
* Ungrouped aggregate will certainly want to read all the tuples,
* and it will deliver a single result row (so leave dNumGroups
* set to 1).
*/
tuple_fraction = 0.0;
}
else if (parse->distinctClause)
{
/*
* Since there was no grouping or aggregation, it's reasonable to
* assume the UNIQUE filter has effects comparable to GROUP BY.
* (If DISTINCT is used with grouping, we ignore its effects for
* rowcount estimation purposes; this amounts to assuming the
* grouped rows are distinct already.)
*/
List *distinctExprs;
distinctExprs = get_sortgrouplist_exprs(parse->distinctClause,
parse->targetList);
dNumGroups = estimate_num_groups(root, distinctExprs, path_rows);
/*
* Adjust tuple_fraction the same way as for GROUP BY, too.
*/
if (tuple_fraction >= 1.0)
tuple_fraction /= dNumGroups;
}
else
{
/*
* Plain non-grouped, non-aggregated query: an absolute tuple
* fraction can be divided by the number of tuples.
*/
if (tuple_fraction >= 1.0)
tuple_fraction /= path_rows;
}
/*
* Pick out the cheapest-total path as well as the cheapest presorted
* path for the requested pathkeys (if there is one). We should take
* the tuple fraction into account when selecting the cheapest
* presorted path, but not when selecting the cheapest-total path,
* since if we have to sort then we'll have to fetch all the tuples.
* (But there's a special case: if query_pathkeys is NIL, meaning
* order doesn't matter, then the "cheapest presorted" path will be
* the cheapest overall for the tuple fraction.)
*/
cheapest_path = final_rel->cheapest_total_path;
sorted_path =
get_cheapest_fractional_path_for_pathkeys(final_rel->pathlist,
root->query_pathkeys,
NULL,
tuple_fraction);
/* Don't consider same path in both guises; just wastes effort */
if (sorted_path == cheapest_path)
sorted_path = NULL;
/*
* Forget about the presorted path if it would be cheaper to sort the
* cheapest-total path. Here we need consider only the behavior at
* the tuple_fraction point. Also, limit_tuples is only relevant if
* not grouping/aggregating, so use root->limit_tuples in the
* cost_sort call.
*/
if (sorted_path)
{
Path sort_path; /* dummy for result of cost_sort */
if (root->query_pathkeys == NIL ||
pathkeys_contained_in(root->query_pathkeys,
cheapest_path->pathkeys))
{
/* No sort needed for cheapest path */
sort_path.startup_cost = cheapest_path->startup_cost;
sort_path.total_cost = cheapest_path->total_cost;
}
else
{
/* Figure cost for sorting */
cost_sort(&sort_path, root, root->query_pathkeys,
cheapest_path->total_cost,
path_rows, path_width,
0.0, work_mem, root->limit_tuples);
}
if (compare_fractional_path_costs(sorted_path, &sort_path,
tuple_fraction) > 0)
{
/* Presorted path is a loser */
sorted_path = NULL;
}
}
/*
* Consider whether we want to use hashing instead of sorting.
*/
if (parse->groupClause)
{
/*
* If grouping, decide whether to use sorted or hashed grouping.
*/
use_hashed_grouping =
choose_hashed_grouping(root,
tuple_fraction, limit_tuples,
path_rows, path_width,
cheapest_path, sorted_path,
dNumGroups, &agg_costs);
/* Also convert # groups to long int --- but 'ware overflow! */
numGroups = (long) Min(dNumGroups, (double) LONG_MAX);
}
else if (parse->distinctClause && sorted_path &&
!root->hasHavingQual && !parse->hasAggs && !activeWindows)
{
/*
* We'll reach the DISTINCT stage without any intermediate
* processing, so figure out whether we will want to hash or not
* so we can choose whether to use cheapest or sorted path.
*/
use_hashed_distinct =
choose_hashed_distinct(root,
tuple_fraction, limit_tuples,
path_rows, path_width,
cheapest_path->startup_cost,
cheapest_path->total_cost,
sorted_path->startup_cost,
sorted_path->total_cost,
sorted_path->pathkeys,
dNumGroups);
tested_hashed_distinct = true;
}
/*
* Select the best path. If we are doing hashed grouping, we will
* always read all the input tuples, so use the cheapest-total path.
* Otherwise, the comparison above is correct.
*/
if (use_hashed_grouping || use_hashed_distinct || !sorted_path)
best_path = cheapest_path;
else
best_path = sorted_path;
/*
* Check to see if it's possible to optimize MIN/MAX aggregates. If
* so, we will forget all the work we did so far to choose a "regular"
* path ... but we had to do it anyway to be able to tell which way is
* cheaper.
*/
result_plan = optimize_minmax_aggregates(root,
tlist,
&agg_costs,
best_path);
if (result_plan != NULL)
{
/*
* optimize_minmax_aggregates generated the full plan, with the
* right tlist, and it has no sort order.
*/
current_pathkeys = NIL;
}
else
{
/*
* Normal case --- create a plan according to query_planner's
* results.
*/
bool need_sort_for_grouping = false;
result_plan = create_plan(root, best_path);
current_pathkeys = best_path->pathkeys;
/* Detect if we'll need an explicit sort for grouping */
if (parse->groupClause && !use_hashed_grouping &&
!pathkeys_contained_in(root->group_pathkeys, current_pathkeys))
{
need_sort_for_grouping = true;
/*
* Always override create_plan's tlist, so that we don't sort
* useless data from a "physical" tlist.
*/
need_tlist_eval = true;
}
/*
* create_plan returns a plan with just a "flat" tlist of required
* Vars. Usually we need to insert the sub_tlist as the tlist of
* the top plan node. However, we can skip that if we determined
* that whatever create_plan chose to return will be good enough.
*/
if (need_tlist_eval)
{
/*
* If the top-level plan node is one that cannot do expression
* evaluation and its existing target list isn't already what
* we need, we must insert a Result node to project the
* desired tlist.
*/
if (!is_projection_capable_plan(result_plan) &&
!tlist_same_exprs(sub_tlist, result_plan->targetlist))
{
result_plan = (Plan *) make_result(root,
sub_tlist,
NULL,
result_plan);
}
else
{
/*
* Otherwise, just replace the subplan's flat tlist with
* the desired tlist.
*/
result_plan->targetlist = sub_tlist;
}
/*
* Also, account for the cost of evaluation of the sub_tlist.
* See comments for add_tlist_costs_to_plan() for more info.
*/
add_tlist_costs_to_plan(root, result_plan, sub_tlist);
}
else
{
/*
* Since we're using create_plan's tlist and not the one
* make_subplanTargetList calculated, we have to refigure any
* grouping-column indexes make_subplanTargetList computed.
*/
locate_grouping_columns(root, tlist, result_plan->targetlist,
groupColIdx);
}
/*
* Insert AGG or GROUP node if needed, plus an explicit sort step
* if necessary.
*
* HAVING clause, if any, becomes qual of the Agg or Group node.
*/
if (use_hashed_grouping)
{
/* Hashed aggregate plan --- no sort needed */
result_plan = (Plan *) make_agg(root,
tlist,
(List *) parse->havingQual,
AGG_HASHED,
&agg_costs,
numGroupCols,
groupColIdx,
extract_grouping_ops(parse->groupClause),
numGroups,
result_plan);
/* Hashed aggregation produces randomly-ordered results */
current_pathkeys = NIL;
}
else if (parse->hasAggs)
{
/* Plain aggregate plan --- sort if needed */
AggStrategy aggstrategy;
if (parse->groupClause)
{
if (need_sort_for_grouping)
{
result_plan = (Plan *)
make_sort_from_groupcols(root,
parse->groupClause,
groupColIdx,
result_plan);
current_pathkeys = root->group_pathkeys;
}
aggstrategy = AGG_SORTED;
/*
* The AGG node will not change the sort ordering of its
* groups, so current_pathkeys describes the result too.
*/
}
else
{
aggstrategy = AGG_PLAIN;
/* Result will be only one row anyway; no sort order */
current_pathkeys = NIL;
}
result_plan = (Plan *) make_agg(root,
tlist,
(List *) parse->havingQual,
aggstrategy,
&agg_costs,
numGroupCols,
groupColIdx,
extract_grouping_ops(parse->groupClause),
numGroups,
result_plan);
}
else if (parse->groupClause)
{
/*
* GROUP BY without aggregation, so insert a group node (plus
* the appropriate sort node, if necessary).
*
* Add an explicit sort if we couldn't make the path come out
* the way the GROUP node needs it.
*/
if (need_sort_for_grouping)
{
result_plan = (Plan *)
make_sort_from_groupcols(root,
parse->groupClause,
groupColIdx,
result_plan);
current_pathkeys = root->group_pathkeys;
}
result_plan = (Plan *) make_group(root,
tlist,
(List *) parse->havingQual,
numGroupCols,
groupColIdx,
extract_grouping_ops(parse->groupClause),
dNumGroups,
result_plan);
/* The Group node won't change sort ordering */
}
else if (root->hasHavingQual)
{
/*
* No aggregates, and no GROUP BY, but we have a HAVING qual.
* This is a degenerate case in which we are supposed to emit
* either 0 or 1 row 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 routine to avoid having to generate the plan in the
* first place.
*/
result_plan = (Plan *) make_result(root,
tlist,
parse->havingQual,
NULL);
}
} /* end of non-minmax-aggregate case */
/*
* Since each window function could require a different sort order, we
* stack up a WindowAgg node for each window, with sort steps between
* them as needed.
*/
if (activeWindows)
{
List *window_tlist;
ListCell *l;
/*
* If the top-level plan node is one that cannot do expression
* evaluation, we must insert a Result node to project the desired
* tlist. (In some cases this might not really be required, but
* it's not worth trying to avoid it. In particular, think not to
* skip adding the Result if the initial window_tlist matches the
* top-level plan node's output, because we might change the tlist
* inside the following loop.) Note that on second and subsequent
* passes through the following loop, the top-level node will be a
* WindowAgg which we know can project; so we only need to check
* once.
*/
if (!is_projection_capable_plan(result_plan))
{
result_plan = (Plan *) make_result(root,
NIL,
NULL,
result_plan);
}
/*
* The "base" targetlist for all steps of the windowing process is
* a flat tlist of all Vars and Aggs needed in 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.) We also add window partitioning and sorting
* expressions to the base tlist, 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_tlist = make_windowInputTargetList(root,
tlist,
activeWindows);
/*
* The copyObject steps here are needed to ensure that each plan
* node has a separately modifiable tlist. (XXX wouldn't a
* shallow list copy do for that?)
*/
result_plan->targetlist = (List *) copyObject(window_tlist);
foreach(l, activeWindows)
{
WindowClause *wc = (WindowClause *) lfirst(l);
List *window_pathkeys;
int partNumCols;
AttrNumber *partColIdx;
Oid *partOperators;
int ordNumCols;
AttrNumber *ordColIdx;
Oid *ordOperators;
window_pathkeys = make_pathkeys_for_window(root,
wc,
tlist);
/*
* This is a bit tricky: we build a sort node even if we don't
* really have to sort. Even when no explicit sort is needed,
* we need to have suitable resjunk items added to the input
* plan's tlist for any partitioning or ordering columns that
* aren't plain Vars. (In theory, make_windowInputTargetList
* should have provided all such columns, but let's not assume
* that here.) Furthermore, this way we can use existing
* infrastructure to identify which input columns are the
* interesting ones.
*/
if (window_pathkeys)
{
Sort *sort_plan;
sort_plan = make_sort_from_pathkeys(root,
result_plan,
window_pathkeys,
-1.0);
if (!pathkeys_contained_in(window_pathkeys,
current_pathkeys))
{
/* we do indeed need to sort */
result_plan = (Plan *) sort_plan;
current_pathkeys = window_pathkeys;
}
/* In either case, extract the per-column information */
get_column_info_for_window(root, wc, tlist,
sort_plan->numCols,
sort_plan->sortColIdx,
&partNumCols,
&partColIdx,
&partOperators,
&ordNumCols,
&ordColIdx,
&ordOperators);
}
else
{
/* empty window specification, nothing to sort */
partNumCols = 0;
partColIdx = NULL;
partOperators = NULL;
ordNumCols = 0;
ordColIdx = NULL;
ordOperators = NULL;
}
if (lnext(l))
{
/* Add the current WindowFuncs to the running tlist */
window_tlist = add_to_flat_tlist(window_tlist,
wflists->windowFuncs[wc->winref]);
}
else
{
/* Install the original tlist in the topmost WindowAgg */
window_tlist = tlist;
}
/* ... and make the WindowAgg plan node */
result_plan = (Plan *)
make_windowagg(root,
(List *) copyObject(window_tlist),
wflists->windowFuncs[wc->winref],
wc->winref,
partNumCols,
partColIdx,
partOperators,
ordNumCols,
ordColIdx,
ordOperators,
wc->frameOptions,
wc->startOffset,
wc->endOffset,
result_plan);
}
}
} /* end of if (setOperations) */
/*
* If there is a DISTINCT clause, add the necessary node(s).
*/
if (parse->distinctClause)
{
double dNumDistinctRows;
long numDistinctRows;
/*
* If there was grouping or aggregation, use the current number of
* rows as the estimated number of DISTINCT rows (ie, assume the
* result was already mostly unique). If not, use the number of
* distinct-groups calculated previously.
*/
if (parse->groupClause || root->hasHavingQual || parse->hasAggs)
dNumDistinctRows = result_plan->plan_rows;
else
dNumDistinctRows = dNumGroups;
/* Also convert to long int --- but 'ware overflow! */
numDistinctRows = (long) Min(dNumDistinctRows, (double) LONG_MAX);
/* Choose implementation method if we didn't already */
if (!tested_hashed_distinct)
{
/*
* At this point, either hashed or sorted grouping will have to
* work from result_plan, so we pass that as both "cheapest" and
* "sorted".
*/
use_hashed_distinct =
choose_hashed_distinct(root,
tuple_fraction, limit_tuples,
result_plan->plan_rows,
result_plan->plan_width,
result_plan->startup_cost,
result_plan->total_cost,
result_plan->startup_cost,
result_plan->total_cost,
current_pathkeys,
dNumDistinctRows);
}
if (use_hashed_distinct)
{
/* Hashed aggregate plan --- no sort needed */
result_plan = (Plan *) make_agg(root,
result_plan->targetlist,
NIL,
AGG_HASHED,
NULL,
list_length(parse->distinctClause),
extract_grouping_cols(parse->distinctClause,
result_plan->targetlist),
extract_grouping_ops(parse->distinctClause),
numDistinctRows,
result_plan);
/* Hashed aggregation produces randomly-ordered results */
current_pathkeys = NIL;
}
else
{
/*
* Use a Unique node to implement DISTINCT. Add an explicit sort
* if we couldn't make the path come out the way the Unique node
* needs it. If we do have to sort, always sort by the more
* rigorous of DISTINCT and ORDER BY, to avoid a second sort
* below. However, for regular DISTINCT, don't sort now if we
* don't have to --- sorting afterwards will likely be cheaper,
* and also has the possibility of optimizing via LIMIT. But for
* DISTINCT ON, we *must* force the final sort now, else it won't
* have the desired behavior.
*/
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;
if (!pathkeys_contained_in(needed_pathkeys, current_pathkeys))
{
if (list_length(root->distinct_pathkeys) >=
list_length(root->sort_pathkeys))
current_pathkeys = root->distinct_pathkeys;
else
{
current_pathkeys = root->sort_pathkeys;
/* Assert checks that parser didn't mess up... */
Assert(pathkeys_contained_in(root->distinct_pathkeys,
current_pathkeys));
}
result_plan = (Plan *) make_sort_from_pathkeys(root,
result_plan,
current_pathkeys,
-1.0);
}
result_plan = (Plan *) make_unique(result_plan,
parse->distinctClause);
result_plan->plan_rows = dNumDistinctRows;
/* The Unique node won't change sort ordering */
}
}
/*
* If ORDER BY was given and we were not able to make the plan come out in
* the right order, add an explicit sort step.
*/
if (parse->sortClause)
{
if (!pathkeys_contained_in(root->sort_pathkeys, current_pathkeys))
{
result_plan = (Plan *) make_sort_from_pathkeys(root,
result_plan,
root->sort_pathkeys,
limit_tuples);
current_pathkeys = root->sort_pathkeys;
}
}
/*
* 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.)
*/
if (parse->rowMarks)
{
result_plan = (Plan *) make_lockrows(result_plan,
root->rowMarks,
SS_assign_special_param(root));
/*
* The result can no longer be assumed sorted, since locking might
* cause the sort key columns to be replaced with new values.
*/
current_pathkeys = NIL;
}
/*
* Finally, if there is a LIMIT/OFFSET clause, add the LIMIT node.
*/
if (limit_needed(parse))
{
result_plan = (Plan *) make_limit(result_plan,
parse->limitOffset,
parse->limitCount,
offset_est,
count_est);
}
/*
* Return the actual output ordering in query_pathkeys for possible use by
* an outer query level.
*/
root->query_pathkeys = current_pathkeys;
return result_plan;
}
/*
* add_tlist_costs_to_plan
*
* Estimate the execution costs associated with evaluating the targetlist
* expressions, and add them to the cost estimates for the Plan node.
*
* If the tlist contains set-returning functions, also inflate the Plan's cost
* and plan_rows estimates accordingly. (Hence, this must be called *after*
* any logic that uses plan_rows to, eg, estimate qual evaluation costs.)
*
* Note: during initial stages of planning, we mostly consider plan nodes with
* "flat" tlists, containing just Vars. So their evaluation cost is zero
* according to the model used by cost_qual_eval() (or if you prefer, the cost
* is factored into cpu_tuple_cost). Thus we can avoid accounting for tlist
* cost throughout query_planner() and subroutines. But once we apply a
* tlist that might contain actual operators, sub-selects, etc, we'd better
* account for its cost. Any set-returning functions in the tlist must also
* affect the estimated rowcount.
*
* Once grouping_planner() has applied a general tlist to the topmost
* scan/join plan node, any tlist eval cost for added-on nodes should be
* accounted for as we create those nodes. Presently, of the node types we
* can add on later, only Agg, WindowAgg, and Group project new tlists (the
* rest just copy their input tuples) --- so make_agg(), make_windowagg() and
* make_group() are responsible for calling this function to account for their
* tlist costs.
*/
void
add_tlist_costs_to_plan(PlannerInfo *root, Plan *plan, List *tlist)
{
QualCost tlist_cost;
double tlist_rows;
cost_qual_eval(&tlist_cost, tlist, root);
plan->startup_cost += tlist_cost.startup;
plan->total_cost += tlist_cost.startup +
tlist_cost.per_tuple * plan->plan_rows;
tlist_rows = tlist_returns_set_rows(tlist);
if (tlist_rows > 1)
{
/*
* We assume that execution costs of the tlist proper were all
* accounted for by cost_qual_eval. 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.
*/
plan->total_cost += plan->plan_rows * (tlist_rows - 1) *
cpu_tuple_cost / 2;
plan->plan_rows *= tlist_rows;
}
}
/*
* 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;
/*
* Similarly, ignore RowMarkClauses for foreign tables; foreign tables
* will instead get ROW_MARK_COPY items in the next loop. (FDWs might
* choose to do something special while fetching their rows, but that
* is of no concern here.)
*/
if (rte->relkind == RELKIND_FOREIGN_TABLE)
continue;
rels = bms_del_member(rels, rc->rti);
newrc = makeNode(PlanRowMark);
newrc->rti = newrc->prti = rc->rti;
newrc->rowmarkId = ++(root->glob->lastRowMarkId);
switch (rc->strength)
{
case LCS_FORUPDATE:
newrc->markType = ROW_MARK_EXCLUSIVE;
break;
case LCS_FORNOKEYUPDATE:
newrc->markType = ROW_MARK_NOKEYEXCLUSIVE;
break;
case LCS_FORSHARE:
newrc->markType = ROW_MARK_SHARE;
break;
case LCS_FORKEYSHARE:
newrc->markType = ROW_MARK_KEYSHARE;
break;
}
newrc->noWait = rc->noWait;
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);
/* real tables support REFERENCE, anything else needs COPY */
if (rte->rtekind == RTE_RELATION &&
rte->relkind != RELKIND_FOREIGN_TABLE)
newrc->markType = ROW_MARK_REFERENCE;
else
newrc->markType = ROW_MARK_COPY;
newrc->noWait = false; /* doesn't matter */
newrc->isParent = false;
prowmarks = lappend(prowmarks, newrc);
}
root->rowMarks = prowmarks;
}
/*
* 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 make_limit, 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; /* less than 0 is same as 0 */
}
}
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);
/* Executor would treat less-than-zero same as zero */
if (offset > 0)
return true; /* OFFSET with a positive value */
}
}
else
return true; /* non-constant OFFSET */
}
return false; /* don't need a Limit plan node */
}
/*
* 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.
*/
static void
preprocess_groupclause(PlannerInfo *root)
{
Query *parse = root->parse;
List *new_groupclause;
bool partial_match;
ListCell *sl;
ListCell *gl;
/* If no ORDER BY, nothing useful to do here */
if (parse->sortClause == NIL)
return;
/*
* 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.
*/
new_groupclause = NIL;
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;
/*
* 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; /* give up, no common sort possible */
if (!OidIsValid(gc->sortop))
return; /* 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));
parse->groupClause = new_groupclause;
}
/*
* 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 (parse->groupClause &&
grouping_is_sortable(parse->groupClause))
root->group_pathkeys =
make_pathkeys_for_sortclauses(root,
parse->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;
}
/*
* choose_hashed_grouping - should we use hashed grouping?
*
* Returns TRUE to select hashing, FALSE to select sorting.
*/
static bool
choose_hashed_grouping(PlannerInfo *root,
double tuple_fraction, double limit_tuples,
double path_rows, int path_width,
Path *cheapest_path, Path *sorted_path,
double dNumGroups, AggClauseCosts *agg_costs)
{
Query *parse = root->parse;
int numGroupCols = list_length(parse->groupClause);
bool can_hash;
bool can_sort;
Size hashentrysize;
List *target_pathkeys;
List *current_pathkeys;
Path hashed_p;
Path sorted_p;
/*
* 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.)
*/
can_hash = (agg_costs->numOrderedAggs == 0 &&
grouping_is_hashable(parse->groupClause));
can_sort = grouping_is_sortable(parse->groupClause);
/* Quick out if only one choice is workable */
if (!(can_hash && can_sort))
{
if (can_hash)
return true;
else if (can_sort)
return false;
else
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.")));
}
/* Prefer sorting when enable_hashagg is off */
if (!enable_hashagg)
return false;
/*
* Don't do it if it doesn't look like the hashtable will fit into
* work_mem.
*/
/* Estimate per-hash-entry space at tuple width... */
hashentrysize = MAXALIGN(path_width) + MAXALIGN(sizeof(MinimalTupleData));
/* 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)
return false;
/*
* When we have both GROUP BY and DISTINCT, use the more-rigorous of
* DISTINCT and ORDER BY as the assumed required output sort order. This
* is an oversimplification because the DISTINCT might get implemented via
* hashing, but it's not clear that the case is common enough (or that our
* estimates are good enough) to justify trying to solve it exactly.
*/
if (list_length(root->distinct_pathkeys) >
list_length(root->sort_pathkeys))
target_pathkeys = root->distinct_pathkeys;
else
target_pathkeys = root->sort_pathkeys;
/*
* See if the estimated cost is no more than doing it the other way. While
* avoiding the need for sorted input is usually a win, the fact that the
* output won't be sorted may be a loss; so we need to do an actual cost
* comparison.
*
* We need to consider cheapest_path + hashagg [+ final sort] versus
* either cheapest_path [+ sort] + group or agg [+ final sort] or
* presorted_path + group or agg [+ final sort] where brackets indicate a
* step that may not be needed. We assume grouping_planner() will have
* passed us a presorted path only if it's a winner compared to
* cheapest_path for this purpose.
*
* These path variables are dummies that just hold cost fields; we don't
* make actual Paths for these steps.
*/
cost_agg(&hashed_p, root, AGG_HASHED, agg_costs,
numGroupCols, dNumGroups,
cheapest_path->startup_cost, cheapest_path->total_cost,
path_rows);
/* Result of hashed agg is always unsorted */
if (target_pathkeys)
cost_sort(&hashed_p, root, target_pathkeys, hashed_p.total_cost,
dNumGroups, path_width,
0.0, work_mem, limit_tuples);
if (sorted_path)
{
sorted_p.startup_cost = sorted_path->startup_cost;
sorted_p.total_cost = sorted_path->total_cost;
current_pathkeys = sorted_path->pathkeys;
}
else
{
sorted_p.startup_cost = cheapest_path->startup_cost;
sorted_p.total_cost = cheapest_path->total_cost;
current_pathkeys = cheapest_path->pathkeys;
}
if (!pathkeys_contained_in(root->group_pathkeys, current_pathkeys))
{
cost_sort(&sorted_p, root, root->group_pathkeys, sorted_p.total_cost,
path_rows, path_width,
0.0, work_mem, -1.0);
current_pathkeys = root->group_pathkeys;
}
if (parse->hasAggs)
cost_agg(&sorted_p, root, AGG_SORTED, agg_costs,
numGroupCols, dNumGroups,
sorted_p.startup_cost, sorted_p.total_cost,
path_rows);
else
cost_group(&sorted_p, root, numGroupCols, dNumGroups,
sorted_p.startup_cost, sorted_p.total_cost,
path_rows);
/* The Agg or Group node will preserve ordering */
if (target_pathkeys &&
!pathkeys_contained_in(target_pathkeys, current_pathkeys))
cost_sort(&sorted_p, root, target_pathkeys, sorted_p.total_cost,
dNumGroups, path_width,
0.0, work_mem, limit_tuples);
/*
* Now make the decision using the top-level tuple fraction.
*/
if (compare_fractional_path_costs(&hashed_p, &sorted_p,
tuple_fraction) < 0)
{
/* Hashed is cheaper, so use it */
return true;
}
return false;
}
/*
* choose_hashed_distinct - should we use hashing for DISTINCT?
*
* This is fairly similar to choose_hashed_grouping, but there are enough
* differences that it doesn't seem worth trying to unify the two functions.
* (One difference is that we sometimes apply this after forming a Plan,
* so the input alternatives can't be represented as Paths --- instead we
* pass in the costs as individual variables.)
*
* But note that making the two choices independently is a bit bogus in
* itself. If the two could be combined into a single choice operation
* it'd probably be better, but that seems far too unwieldy to be practical,
* especially considering that the combination of GROUP BY and DISTINCT
* isn't very common in real queries. By separating them, we are giving
* extra preference to using a sorting implementation when a common sort key
* is available ... and that's not necessarily wrong anyway.
*
* Returns TRUE to select hashing, FALSE to select sorting.
*/
static bool
choose_hashed_distinct(PlannerInfo *root,
double tuple_fraction, double limit_tuples,
double path_rows, int path_width,
Cost cheapest_startup_cost, Cost cheapest_total_cost,
Cost sorted_startup_cost, Cost sorted_total_cost,
List *sorted_pathkeys,
double dNumDistinctRows)
{
Query *parse = root->parse;
int numDistinctCols = list_length(parse->distinctClause);
bool can_sort;
bool can_hash;
Size hashentrysize;
List *current_pathkeys;
List *needed_pathkeys;
Path hashed_p;
Path sorted_p;
/*
* If we have a sortable DISTINCT ON clause, we always use sorting. This
* enforces the expected behavior of DISTINCT ON.
*/
can_sort = grouping_is_sortable(parse->distinctClause);
if (can_sort && parse->hasDistinctOn)
return false;
can_hash = grouping_is_hashable(parse->distinctClause);
/* Quick out if only one choice is workable */
if (!(can_hash && can_sort))
{
if (can_hash)
return true;
else if (can_sort)
return false;
else
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.")));
}
/* Prefer sorting when enable_hashagg is off */
if (!enable_hashagg)
return false;
/*
* Don't do it if it doesn't look like the hashtable will fit into
* work_mem.
*/
/* Estimate per-hash-entry space at tuple width... */
hashentrysize = MAXALIGN(path_width) + MAXALIGN(sizeof(MinimalTupleData));
/* plus the per-hash-entry overhead */
hashentrysize += hash_agg_entry_size(0);
if (hashentrysize * dNumDistinctRows > work_mem * 1024L)
return false;
/*
* See if the estimated cost is no more than doing it the other way. While
* avoiding the need for sorted input is usually a win, the fact that the
* output won't be sorted may be a loss; so we need to do an actual cost
* comparison.
*
* We need to consider cheapest_path + hashagg [+ final sort] versus
* sorted_path [+ sort] + group [+ final sort] where brackets indicate a
* step that may not be needed.
*
* These path variables are dummies that just hold cost fields; we don't
* make actual Paths for these steps.
*/
cost_agg(&hashed_p, root, AGG_HASHED, NULL,
numDistinctCols, dNumDistinctRows,
cheapest_startup_cost, cheapest_total_cost,
path_rows);
/*
* Result of hashed agg is always unsorted, so if ORDER BY is present we
* need to charge for the final sort.
*/
if (parse->sortClause)
cost_sort(&hashed_p, root, root->sort_pathkeys, hashed_p.total_cost,
dNumDistinctRows, path_width,
0.0, work_mem, limit_tuples);
/*
* Now for the GROUP case. See comments in grouping_planner about the
* sorting choices here --- this code should match that code.
*/
sorted_p.startup_cost = sorted_startup_cost;
sorted_p.total_cost = sorted_total_cost;
current_pathkeys = sorted_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;
if (!pathkeys_contained_in(needed_pathkeys, current_pathkeys))
{
if (list_length(root->distinct_pathkeys) >=
list_length(root->sort_pathkeys))
current_pathkeys = root->distinct_pathkeys;
else
current_pathkeys = root->sort_pathkeys;
cost_sort(&sorted_p, root, current_pathkeys, sorted_p.total_cost,
path_rows, path_width,
0.0, work_mem, -1.0);
}
cost_group(&sorted_p, root, numDistinctCols, dNumDistinctRows,
sorted_p.startup_cost, sorted_p.total_cost,
path_rows);
if (parse->sortClause &&
!pathkeys_contained_in(root->sort_pathkeys, current_pathkeys))
cost_sort(&sorted_p, root, root->sort_pathkeys, sorted_p.total_cost,
dNumDistinctRows, path_width,
0.0, work_mem, limit_tuples);
/*
* Now make the decision using the top-level tuple fraction.
*/
if (compare_fractional_path_costs(&hashed_p, &sorted_p,
tuple_fraction) < 0)
{
/* Hashed is cheaper, so use it */
return true;
}
return false;
}
/*
* make_subplanTargetList
* Generate appropriate target list when grouping is required.
*
* When grouping_planner inserts grouping or aggregation plan nodes
* above the scan/join plan constructed by query_planner+create_plan,
* we typically want the scan/join plan to emit a different target list
* than the outer plan nodes should have. This routine generates the
* correct target list for the scan/join subplan.
*
* The initial 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; the other expressions
* will be computed by the inserted 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.
*
* If we are grouping or aggregating, *and* there are no non-Var grouping
* expressions, then the returned tlist is effectively dummy; we do not
* need to force it to be evaluated, because all the Vars it contains
* should be present in the "flat" tlist generated by create_plan, though
* possibly in a different order. In that case we'll use create_plan's tlist,
* and the tlist made here is only needed as input to query_planner to tell
* it which Vars are needed in the output of the scan/join plan.
*
* 'tlist' is the query's target list.
* 'groupColIdx' receives an array of column numbers for the GROUP BY
* expressions (if there are any) in the returned target list.
* 'need_tlist_eval' is set true if we really need to evaluate the
* returned tlist as-is. (Note: locate_grouping_columns assumes
* that if this is FALSE, all grouping columns are simple Vars.)
*
* The result is the targetlist to be passed to query_planner.
*/
static List *
make_subplanTargetList(PlannerInfo *root,
List *tlist,
AttrNumber **groupColIdx,
bool *need_tlist_eval)
{
Query *parse = root->parse;
List *sub_tlist;
List *non_group_cols;
List *non_group_vars;
int numCols;
*groupColIdx = NULL;
/*
* If we're not grouping or aggregating, there's nothing to do here;
* query_planner should receive the unmodified target list.
*/
if (!parse->hasAggs && !parse->groupClause && !root->hasHavingQual &&
!parse->hasWindowFuncs)
{
*need_tlist_eval = true;
return tlist;
}
/*
* Otherwise, we must build a tlist containing all grouping columns, plus
* any other Vars mentioned in the targetlist and HAVING qual.
*/
sub_tlist = NIL;
non_group_cols = NIL;
*need_tlist_eval = false; /* only eval if not flat tlist */
numCols = list_length(parse->groupClause);
if (numCols > 0)
{
/*
* If grouping, create sub_tlist entries for all GROUP BY columns, and
* make an array showing where the group columns are in the sub_tlist.
*
* Note: with this implementation, the array entries will always be
* 1..N, but we don't want callers to assume that.
*/
AttrNumber *grpColIdx;
ListCell *tl;
grpColIdx = (AttrNumber *) palloc0(sizeof(AttrNumber) * numCols);
*groupColIdx = grpColIdx;
foreach(tl, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(tl);
int colno;
colno = get_grouping_column_index(parse, tle);
if (colno >= 0)
{
/*
* It's a grouping column, so add it to the result tlist and
* remember its resno in grpColIdx[].
*/
TargetEntry *newtle;
newtle = makeTargetEntry(tle->expr,
list_length(sub_tlist) + 1,
NULL,
false);
sub_tlist = lappend(sub_tlist, newtle);
Assert(grpColIdx[colno] == 0); /* no dups expected */
grpColIdx[colno] = newtle->resno;
if (!(newtle->expr && IsA(newtle->expr, Var)))
*need_tlist_eval = true; /* tlist contains non Vars */
}
else
{
/*
* Non-grouping column, so just remember the expression for
* later call to pull_var_clause. There's no need for
* pull_var_clause to examine the TargetEntry node itself.
*/
non_group_cols = lappend(non_group_cols, tle->expr);
}
}
}
else
{
/*
* With no grouping columns, just pass whole tlist to pull_var_clause.
* Need (shallow) copy to avoid damaging input tlist below.
*/
non_group_cols = list_copy(tlist);
}
/*
* 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 result tlist 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 will be
* pulled out here, too.
*/
non_group_vars = pull_var_clause((Node *) non_group_cols,
PVC_RECURSE_AGGREGATES,
PVC_INCLUDE_PLACEHOLDERS);
sub_tlist = add_to_flat_tlist(sub_tlist, non_group_vars);
/* clean up cruft */
list_free(non_group_vars);
list_free(non_group_cols);
return sub_tlist;
}
/*
* get_grouping_column_index
* Get the GROUP BY column position, if any, of a targetlist entry.
*
* Returns the index (counting from 0) of the TLE in the GROUP BY list, or -1
* if it's not a grouping column. Note: the result is unique because the
* parser won't make multiple groupClause entries for the same TLE.
*/
static int
get_grouping_column_index(Query *parse, TargetEntry *tle)
{
int colno = 0;
Index ressortgroupref = tle->ressortgroupref;
ListCell *gl;
/* No need to search groupClause if TLE hasn't got a sortgroupref */
if (ressortgroupref == 0)
return -1;
foreach(gl, parse->groupClause)
{
SortGroupClause *grpcl = (SortGroupClause *) lfirst(gl);
if (grpcl->tleSortGroupRef == ressortgroupref)
return colno;
colno++;
}
return -1;
}
/*
* locate_grouping_columns
* Locate grouping columns in the tlist chosen by create_plan.
*
* This is only needed if we don't use the sub_tlist chosen by
* make_subplanTargetList. We have to forget the column indexes found
* by that routine and re-locate the grouping exprs in the real sub_tlist.
* We assume the grouping exprs are just Vars (see make_subplanTargetList).
*/
static void
locate_grouping_columns(PlannerInfo *root,
List *tlist,
List *sub_tlist,
AttrNumber *groupColIdx)
{
int keyno = 0;
ListCell *gl;
/*
* No work unless grouping.
*/
if (!root->parse->groupClause)
{
Assert(groupColIdx == NULL);
return;
}
Assert(groupColIdx != NULL);
foreach(gl, root->parse->groupClause)
{
SortGroupClause *grpcl = (SortGroupClause *) lfirst(gl);
Var *groupexpr = (Var *) get_sortgroupclause_expr(grpcl, tlist);
TargetEntry *te;
/*
* The grouping column returned by create_plan might not have the same
* typmod as the original Var. (This can happen in cases where a
* set-returning function has been inlined, so that we now have more
* knowledge about what it returns than we did when the original Var
* was created.) So we can't use tlist_member() to search the tlist;
* instead use tlist_member_match_var. For safety, still check that
* the vartype matches.
*/
if (!(groupexpr && IsA(groupexpr, Var)))
elog(ERROR, "grouping column is not a Var as expected");
te = tlist_member_match_var(groupexpr, sub_tlist);
if (!te)
elog(ERROR, "failed to locate grouping columns");
Assert(((Var *) te->expr)->vartype == groupexpr->vartype);
groupColIdx[keyno++] = te->resno;
}
}
/*
* 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_windowInputTargetList
* Generate appropriate target list for initial input to WindowAgg nodes.
*
* When grouping_planner inserts one or more WindowAgg nodes into the plan,
* this function computes the initial target list to be computed by the node
* just below the first WindowAgg. This list 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 tlist;
* only the topmost WindowAgg computes the actual desired target list.
*
* This function is much like make_subplanTargetList, 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_subplanTargetList, because we may no longer have access to the
* individual Vars in them.
*
* Another key difference from make_subplanTargetList 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.
*
* 'tlist' is the query's final target list.
* 'activeWindows' is the list of active windows previously identified by
* select_active_windows.
*
* The result is the targetlist to be computed by the plan node immediately
* below the first WindowAgg node.
*/
static List *
make_windowInputTargetList(PlannerInfo *root,
List *tlist,
List *activeWindows)
{
Query *parse = root->parse;
Bitmapset *sgrefs;
List *new_tlist;
List *flattenable_cols;
List *flattenable_vars;
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 tlist containing all the non-flattenable tlist items, and
* save aside the others for a moment.
*/
new_tlist = NIL;
flattenable_cols = NIL;
foreach(lc, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(lc);
/*
* 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 (tle->ressortgroupref != 0 &&
bms_is_member(tle->ressortgroupref, sgrefs))
{
/* Don't want to deconstruct this value, so add to new_tlist */
TargetEntry *newtle;
newtle = makeTargetEntry(tle->expr,
list_length(new_tlist) + 1,
NULL,
false);
/* Preserve its sortgroupref marking, in case it's volatile */
newtle->ressortgroupref = tle->ressortgroupref;
new_tlist = lappend(new_tlist, newtle);
}
else
{
/*
* Column is to be flattened, so just remember the expression for
* later call to pull_var_clause. There's no need for
* pull_var_clause to examine the TargetEntry node itself.
*/
flattenable_cols = lappend(flattenable_cols, tle->expr);
}
}
/*
* Pull out all the Vars and Aggrefs mentioned in flattenable columns, and
* add them to the result tlist 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 the
* Aggrefs are placed in the Agg node's tlist and not left to be computed
* at higher levels.
*/
flattenable_vars = pull_var_clause((Node *) flattenable_cols,
PVC_INCLUDE_AGGREGATES,
PVC_INCLUDE_PLACEHOLDERS);
new_tlist = add_to_flat_tlist(new_tlist, flattenable_vars);
/* clean up cruft */
list_free(flattenable_vars);
list_free(flattenable_cols);
return new_tlist;
}
/*
* 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.
*/
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;
}
/*----------
* get_column_info_for_window
* Get the partitioning/ordering column numbers and equality operators
* for a WindowAgg node.
*
* This depends on the behavior of make_pathkeys_for_window()!
*
* We are given the target WindowClause and an array of the input column
* numbers associated with the resulting pathkeys. In the easy case, there
* are the same number of pathkey columns as partitioning + ordering columns
* and we just have to copy some data around. However, it's possible that
* some of the original partitioning + ordering columns were eliminated as
* redundant during the transformation to pathkeys. (This can happen even
* though the parser gets rid of obvious duplicates. A typical scenario is a
* window specification "PARTITION BY x ORDER BY y" coupled with a clause
* "WHERE x = y" that causes the two sort columns to be recognized as
* redundant.) In that unusual case, we have to work a lot harder to
* determine which keys are significant.
*
* The method used here is a bit brute-force: add the sort columns to a list
* one at a time and note when the resulting pathkey list gets longer. But
* it's a sufficiently uncommon case that a faster way doesn't seem worth
* the amount of code refactoring that'd be needed.
*----------
*/
static void
get_column_info_for_window(PlannerInfo *root, WindowClause *wc, List *tlist,
int numSortCols, AttrNumber *sortColIdx,
int *partNumCols,
AttrNumber **partColIdx,
Oid **partOperators,
int *ordNumCols,
AttrNumber **ordColIdx,
Oid **ordOperators)
{
int numPart = list_length(wc->partitionClause);
int numOrder = list_length(wc->orderClause);
if (numSortCols == numPart + numOrder)
{
/* easy case */
*partNumCols = numPart;
*partColIdx = sortColIdx;
*partOperators = extract_grouping_ops(wc->partitionClause);
*ordNumCols = numOrder;
*ordColIdx = sortColIdx + numPart;
*ordOperators = extract_grouping_ops(wc->orderClause);
}
else
{
List *sortclauses;
List *pathkeys;
int scidx;
ListCell *lc;
/* first, allocate what's certainly enough space for the arrays */
*partNumCols = 0;
*partColIdx = (AttrNumber *) palloc(numPart * sizeof(AttrNumber));
*partOperators = (Oid *) palloc(numPart * sizeof(Oid));
*ordNumCols = 0;
*ordColIdx = (AttrNumber *) palloc(numOrder * sizeof(AttrNumber));
*ordOperators = (Oid *) palloc(numOrder * sizeof(Oid));
sortclauses = NIL;
pathkeys = NIL;
scidx = 0;
foreach(lc, wc->partitionClause)
{
SortGroupClause *sgc = (SortGroupClause *) lfirst(lc);
List *new_pathkeys;
sortclauses = lappend(sortclauses, sgc);
new_pathkeys = make_pathkeys_for_sortclauses(root,
sortclauses,
tlist);
if (list_length(new_pathkeys) > list_length(pathkeys))
{
/* this sort clause is actually significant */
(*partColIdx)[*partNumCols] = sortColIdx[scidx++];
(*partOperators)[*partNumCols] = sgc->eqop;
(*partNumCols)++;
pathkeys = new_pathkeys;
}
}
foreach(lc, wc->orderClause)
{
SortGroupClause *sgc = (SortGroupClause *) lfirst(lc);
List *new_pathkeys;
sortclauses = lappend(sortclauses, sgc);
new_pathkeys = make_pathkeys_for_sortclauses(root,
sortclauses,
tlist);
if (list_length(new_pathkeys) > list_length(pathkeys))
{
/* this sort clause is actually significant */
(*ordColIdx)[*ordNumCols] = sortColIdx[scidx++];
(*ordOperators)[*ordNumCols] = sgc->eqop;
(*ordNumCols)++;
pathkeys = new_pathkeys;
}
}
/* complain if we didn't eat exactly the right number of sort cols */
if (scidx != numSortCols)
elog(ERROR, "failed to deconstruct sort operators into partitioning/ordering operators");
}
}
/*
* 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->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);
cost_sort(&seqScanAndSortPath, root, NIL,
seqScanPath->total_cost, rel->tuples, rel->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);
}
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