database/postgres
database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-05-28 05:21:27 +03:00
Code
postgres/src/backend/optimizer/plan/initsplan.c
Tom Lane 364a9f47ab Refactor pull_var_clause's API to make it less tedious to extend. 
In commit 1d97c19a0f748e94 and later c1d9579dd8bf3c92, we extended
pull_var_clause's API by adding enum-type arguments.  That's sort of a pain
to maintain, though, because it means every time we add a new behavior we
must touch every last one of the call sites, even if there's a reasonable
default behavior that most of them could use.  Let's switch over to using a
bitmask of flags, instead; that seems more maintainable and might save a
nanosecond or two as well.  This commit changes no behavior in itself,
though I'm going to follow it up with one that does add a new behavior.

In passing, remove flatten_tlist(), which has not been used since 9.1
and would otherwise need the same API changes.

Removing these enums means that optimizer/tlist.h no longer needs to
depend on optimizer/var.h.  Changing that caused a number of C files to
need addition of #include "optimizer/var.h" (probably we can thank old
runs of pgrminclude for that); but on balance it seems like a good change
anyway.
2016-03-10 15:53:07 -05:00

2356 lines
79 KiB
C
Raw Blame History

/*-------------------------------------------------------------------------
*
* initsplan.c
* Target list, qualification, joininfo initialization routines
*
* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/plan/initsplan.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "catalog/pg_type.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/joininfo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/placeholder.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/var.h"
#include "parser/analyze.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"
/* These parameters are set by GUC */
int from_collapse_limit;
int join_collapse_limit;
/* Elements of the postponed_qual_list used during deconstruct_recurse */
typedef struct PostponedQual
{
Node *qual; /* a qual clause waiting to be processed */
Relids relids; /* the set of baserels it references */
} PostponedQual;
static void extract_lateral_references(PlannerInfo *root, RelOptInfo *brel,
Index rtindex);
static List *deconstruct_recurse(PlannerInfo *root, Node *jtnode,
bool below_outer_join,
Relids *qualscope, Relids *inner_join_rels,
List **postponed_qual_list);
static SpecialJoinInfo *make_outerjoininfo(PlannerInfo *root,
Relids left_rels, Relids right_rels,
Relids inner_join_rels,
JoinType jointype, List *clause);
static void compute_semijoin_info(SpecialJoinInfo *sjinfo, List *clause);
static void distribute_qual_to_rels(PlannerInfo *root, Node *clause,
bool is_deduced,
bool below_outer_join,
JoinType jointype,
Relids qualscope,
Relids ojscope,
Relids outerjoin_nonnullable,
Relids deduced_nullable_relids,
List **postponed_qual_list);
static bool check_outerjoin_delay(PlannerInfo *root, Relids *relids_p,
Relids *nullable_relids_p, bool is_pushed_down);
static bool check_equivalence_delay(PlannerInfo *root,
RestrictInfo *restrictinfo);
static bool check_redundant_nullability_qual(PlannerInfo *root, Node *clause);
static void check_mergejoinable(RestrictInfo *restrictinfo);
static void check_hashjoinable(RestrictInfo *restrictinfo);
/*****************************************************************************
*
* JOIN TREES
*
*****************************************************************************/
/*
* add_base_rels_to_query
*
* Scan the query's jointree and create baserel RelOptInfos for all
* the base relations (ie, table, subquery, and function RTEs)
* appearing in the jointree.
*
* The initial invocation must pass root->parse->jointree as the value of
* jtnode. Internally, the function recurses through the jointree.
*
* At the end of this process, there should be one baserel RelOptInfo for
* every non-join RTE that is used in the query. Therefore, this routine
* is the only place that should call build_simple_rel with reloptkind
* RELOPT_BASEREL. (Note: build_simple_rel recurses internally to build
* "other rel" RelOptInfos for the members of any appendrels we find here.)
*/
void
add_base_rels_to_query(PlannerInfo *root, Node *jtnode)
{
if (jtnode == NULL)
return;
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
(void) build_simple_rel(root, varno, RELOPT_BASEREL);
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
ListCell *l;
foreach(l, f->fromlist)
add_base_rels_to_query(root, lfirst(l));
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
add_base_rels_to_query(root, j->larg);
add_base_rels_to_query(root, j->rarg);
}
else
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
}
/*****************************************************************************
*
* TARGET LISTS
*
*****************************************************************************/
/*
* build_base_rel_tlists
* Add targetlist entries for each var needed in the query's final tlist
* (and HAVING clause, if any) to the appropriate base relations.
*
* We mark such vars as needed by "relation 0" to ensure that they will
* propagate up through all join plan steps.
*/
void
build_base_rel_tlists(PlannerInfo *root, List *final_tlist)
{
List *tlist_vars = pull_var_clause((Node *) final_tlist,
PVC_RECURSE_AGGREGATES |
PVC_INCLUDE_PLACEHOLDERS);
if (tlist_vars != NIL)
{
add_vars_to_targetlist(root, tlist_vars, bms_make_singleton(0), true);
list_free(tlist_vars);
}
/*
* If there's a HAVING clause, we'll need the Vars it uses, too.
*/
if (root->parse->havingQual)
{
List *having_vars = pull_var_clause(root->parse->havingQual,
PVC_RECURSE_AGGREGATES |
PVC_INCLUDE_PLACEHOLDERS);
if (having_vars != NIL)
{
add_vars_to_targetlist(root, having_vars,
bms_make_singleton(0), true);
list_free(having_vars);
}
}
}
/*
* add_vars_to_targetlist
* For each variable appearing in the list, add it to the owning
* relation's targetlist if not already present, and mark the variable
* as being needed for the indicated join (or for final output if
* where_needed includes "relation 0").
*
* The list may also contain PlaceHolderVars. These don't necessarily
* have a single owning relation; we keep their attr_needed info in
* root->placeholder_list instead. If create_new_ph is true, it's OK
* to create new PlaceHolderInfos; otherwise, the PlaceHolderInfos must
* already exist, and we should only update their ph_needed. (This should
* be true before deconstruct_jointree begins, and false after that.)
*/
void
add_vars_to_targetlist(PlannerInfo *root, List *vars,
Relids where_needed, bool create_new_ph)
{
ListCell *temp;
Assert(!bms_is_empty(where_needed));
foreach(temp, vars)
{
Node *node = (Node *) lfirst(temp);
if (IsA(node, Var))
{
Var *var = (Var *) node;
RelOptInfo *rel = find_base_rel(root, var->varno);
int attno = var->varattno;
if (bms_is_subset(where_needed, rel->relids))
continue;
Assert(attno >= rel->min_attr && attno <= rel->max_attr);
attno -= rel->min_attr;
if (rel->attr_needed[attno] == NULL)
{
/* Variable not yet requested, so add to rel's targetlist */
/* XXX is copyObject necessary here? */
rel->reltarget.exprs = lappend(rel->reltarget.exprs,
copyObject(var));
/* reltarget cost and width will be computed later */
}
rel->attr_needed[attno] = bms_add_members(rel->attr_needed[attno],
where_needed);
}
else if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv,
create_new_ph);
phinfo->ph_needed = bms_add_members(phinfo->ph_needed,
where_needed);
}
else
elog(ERROR, "unrecognized node type: %d", (int) nodeTag(node));
}
}
/*****************************************************************************
*
* LATERAL REFERENCES
*
*****************************************************************************/
/*
* find_lateral_references
* For each LATERAL subquery, extract all its references to Vars and
* PlaceHolderVars of the current query level, and make sure those values
* will be available for evaluation of the subquery.
*
* While later planning steps ensure that the Var/PHV source rels are on the
* outside of nestloops relative to the LATERAL subquery, we also need to
* ensure that the Vars/PHVs propagate up to the nestloop join level; this
* means setting suitable where_needed values for them.
*
* Note that this only deals with lateral references in unflattened LATERAL
* subqueries. When we flatten a LATERAL subquery, its lateral references
* become plain Vars in the parent query, but they may have to be wrapped in
* PlaceHolderVars if they need to be forced NULL by outer joins that don't
* also null the LATERAL subquery. That's all handled elsewhere.
*
* This has to run before deconstruct_jointree, since it might result in
* creation of PlaceHolderInfos.
*/
void
find_lateral_references(PlannerInfo *root)
{
Index rti;
/* We need do nothing if the query contains no LATERAL RTEs */
if (!root->hasLateralRTEs)
return;
/*
* Examine all baserels (the rel array has been set up by now).
*/
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *brel = root->simple_rel_array[rti];
/* there may be empty slots corresponding to non-baserel RTEs */
if (brel == NULL)
continue;
Assert(brel->relid == rti); /* sanity check on array */
/*
* This bit is less obvious than it might look. We ignore appendrel
* otherrels and consider only their parent baserels. In a case where
* a LATERAL-containing UNION ALL subquery was pulled up, it is the
* otherrel that is actually going to be in the plan. However, we
* want to mark all its lateral references as needed by the parent,
* because it is the parent's relid that will be used for join
* planning purposes. And the parent's RTE will contain all the
* lateral references we need to know, since the pulled-up member is
* nothing but a copy of parts of the original RTE's subquery. We
* could visit the parent's children instead and transform their
* references back to the parent's relid, but it would be much more
* complicated for no real gain. (Important here is that the child
* members have not yet received any processing beyond being pulled
* up.) Similarly, in appendrels created by inheritance expansion,
* it's sufficient to look at the parent relation.
*/
/* ignore RTEs that are "other rels" */
if (brel->reloptkind != RELOPT_BASEREL)
continue;
extract_lateral_references(root, brel, rti);
}
}
static void
extract_lateral_references(PlannerInfo *root, RelOptInfo *brel, Index rtindex)
{
RangeTblEntry *rte = root->simple_rte_array[rtindex];
List *vars;
List *newvars;
Relids where_needed;
ListCell *lc;
/* No cross-references are possible if it's not LATERAL */
if (!rte->lateral)
return;
/* Fetch the appropriate variables */
if (rte->rtekind == RTE_RELATION)
vars = pull_vars_of_level((Node *) rte->tablesample, 0);
else if (rte->rtekind == RTE_SUBQUERY)
vars = pull_vars_of_level((Node *) rte->subquery, 1);
else if (rte->rtekind == RTE_FUNCTION)
vars = pull_vars_of_level((Node *) rte->functions, 0);
else if (rte->rtekind == RTE_VALUES)
vars = pull_vars_of_level((Node *) rte->values_lists, 0);
else
{
Assert(false);
return; /* keep compiler quiet */
}
if (vars == NIL)
return; /* nothing to do */
/* Copy each Var (or PlaceHolderVar) and adjust it to match our level */
newvars = NIL;
foreach(lc, vars)
{
Node *node = (Node *) lfirst(lc);
node = copyObject(node);
if (IsA(node, Var))
{
Var *var = (Var *) node;
/* Adjustment is easy since it's just one node */
var->varlevelsup = 0;
}
else if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
int levelsup = phv->phlevelsup;
/* Have to work harder to adjust the contained expression too */
if (levelsup != 0)
IncrementVarSublevelsUp(node, -levelsup, 0);
/*
* If we pulled the PHV out of a subquery RTE, its expression
* needs to be preprocessed. subquery_planner() already did this
* for level-zero PHVs in function and values RTEs, though.
*/
if (levelsup > 0)
phv->phexpr = preprocess_phv_expression(root, phv->phexpr);
}
else
Assert(false);
newvars = lappend(newvars, node);
}
list_free(vars);
/*
* We mark the Vars as being "needed" at the LATERAL RTE. This is a bit
* of a cheat: a more formal approach would be to mark each one as needed
* at the join of the LATERAL RTE with its source RTE. But it will work,
* and it's much less tedious than computing a separate where_needed for
* each Var.
*/
where_needed = bms_make_singleton(rtindex);
/*
* Push Vars into their source relations' targetlists, and PHVs into
* root->placeholder_list.
*/
add_vars_to_targetlist(root, newvars, where_needed, true);
/* Remember the lateral references for create_lateral_join_info */
brel->lateral_vars = newvars;
}
/*
* create_lateral_join_info
* Fill in the per-base-relation direct_lateral_relids, lateral_relids
* and lateral_referencers sets.
*
* This has to run after deconstruct_jointree, because we need to know the
* final ph_eval_at values for PlaceHolderVars.
*/
void
create_lateral_join_info(PlannerInfo *root)
{
bool found_laterals = false;
Index rti;
ListCell *lc;
/* We need do nothing if the query contains no LATERAL RTEs */
if (!root->hasLateralRTEs)
return;
/*
* Examine all baserels (the rel array has been set up by now).
*/
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *brel = root->simple_rel_array[rti];
Relids lateral_relids;
/* there may be empty slots corresponding to non-baserel RTEs */
if (brel == NULL)
continue;
Assert(brel->relid == rti); /* sanity check on array */
/* ignore RTEs that are "other rels" */
if (brel->reloptkind != RELOPT_BASEREL)
continue;
lateral_relids = NULL;
/* consider each laterally-referenced Var or PHV */
foreach(lc, brel->lateral_vars)
{
Node *node = (Node *) lfirst(lc);
if (IsA(node, Var))
{
Var *var = (Var *) node;
found_laterals = true;
lateral_relids = bms_add_member(lateral_relids,
var->varno);
}
else if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv,
false);
found_laterals = true;
lateral_relids = bms_add_members(lateral_relids,
phinfo->ph_eval_at);
}
else
Assert(false);
}
/* We now have all the simple lateral refs from this rel */
brel->direct_lateral_relids = lateral_relids;
brel->lateral_relids = bms_copy(lateral_relids);
}
/*
* Now check for lateral references within PlaceHolderVars, and mark their
* eval_at rels as having lateral references to the source rels.
*
* For a PHV that is due to be evaluated at a baserel, mark its source(s)
* as direct lateral dependencies of the baserel (adding onto the ones
* recorded above). If it's due to be evaluated at a join, mark its
* source(s) as indirect lateral dependencies of each baserel in the join,
* ie put them into lateral_relids but not direct_lateral_relids. This is
* appropriate because we can't put any such baserel on the outside of a
* join to one of the PHV's lateral dependencies, but on the other hand we
* also can't yet join it directly to the dependency.
*/
foreach(lc, root->placeholder_list)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
Relids eval_at = phinfo->ph_eval_at;
int varno;
if (phinfo->ph_lateral == NULL)
continue; /* PHV is uninteresting if no lateral refs */
found_laterals = true;
if (bms_get_singleton_member(eval_at, &varno))
{
/* Evaluation site is a baserel */
RelOptInfo *brel = find_base_rel(root, varno);
brel->direct_lateral_relids =
bms_add_members(brel->direct_lateral_relids,
phinfo->ph_lateral);
brel->lateral_relids =
bms_add_members(brel->lateral_relids,
phinfo->ph_lateral);
}
else
{
/* Evaluation site is a join */
varno = -1;
while ((varno = bms_next_member(eval_at, varno)) >= 0)
{
RelOptInfo *brel = find_base_rel(root, varno);
brel->lateral_relids = bms_add_members(brel->lateral_relids,
phinfo->ph_lateral);
}
}
}
/*
* If we found no actual lateral references, we're done; but reset the
* hasLateralRTEs flag to avoid useless work later.
*/
if (!found_laterals)
{
root->hasLateralRTEs = false;
return;
}
/*
* Calculate the transitive closure of the lateral_relids sets, so that
* they describe both direct and indirect lateral references. If relation
* X references Y laterally, and Y references Z laterally, then we will
* have to scan X on the inside of a nestloop with Z, so for all intents
* and purposes X is laterally dependent on Z too.
*
* This code is essentially Warshall's algorithm for transitive closure.
* The outer loop considers each baserel, and propagates its lateral
* dependencies to those baserels that have a lateral dependency on it.
*/
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *brel = root->simple_rel_array[rti];
Relids outer_lateral_relids;
Index rti2;
if (brel == NULL || brel->reloptkind != RELOPT_BASEREL)
continue;
/* need not consider baserel further if it has no lateral refs */
outer_lateral_relids = brel->lateral_relids;
if (outer_lateral_relids == NULL)
continue;
/* else scan all baserels */
for (rti2 = 1; rti2 < root->simple_rel_array_size; rti2++)
{
RelOptInfo *brel2 = root->simple_rel_array[rti2];
if (brel2 == NULL || brel2->reloptkind != RELOPT_BASEREL)
continue;
/* if brel2 has lateral ref to brel, propagate brel's refs */
if (bms_is_member(rti, brel2->lateral_relids))
brel2->lateral_relids = bms_add_members(brel2->lateral_relids,
outer_lateral_relids);
}
}
/*
* Now that we've identified all lateral references, mark each baserel
* with the set of relids of rels that reference it laterally (possibly
* indirectly) --- that is, the inverse mapping of lateral_relids.
*/
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *brel = root->simple_rel_array[rti];
Relids lateral_relids;
int rti2;
if (brel == NULL || brel->reloptkind != RELOPT_BASEREL)
continue;
/* Nothing to do at rels with no lateral refs */
lateral_relids = brel->lateral_relids;
if (lateral_relids == NULL)
continue;
/*
* We should not have broken the invariant that lateral_relids is
* exactly NULL if empty.
*/
Assert(!bms_is_empty(lateral_relids));
/* Also, no rel should have a lateral dependency on itself */
Assert(!bms_is_member(rti, lateral_relids));
/* Mark this rel's referencees */
rti2 = -1;
while ((rti2 = bms_next_member(lateral_relids, rti2)) >= 0)
{
RelOptInfo *brel2 = root->simple_rel_array[rti2];
Assert(brel2 != NULL && brel2->reloptkind == RELOPT_BASEREL);
brel2->lateral_referencers =
bms_add_member(brel2->lateral_referencers, rti);
}
}
/*
* Lastly, propagate lateral_relids and lateral_referencers from appendrel
* parent rels to their child rels. We intentionally give each child rel
* the same minimum parameterization, even though it's quite possible that
* some don't reference all the lateral rels. This is because any append
* path for the parent will have to have the same parameterization for
* every child anyway, and there's no value in forcing extra
* reparameterize_path() calls. Similarly, a lateral reference to the
* parent prevents use of otherwise-movable join rels for each child.
*/
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *brel = root->simple_rel_array[rti];
if (brel == NULL || brel->reloptkind != RELOPT_BASEREL)
continue;
if (root->simple_rte_array[rti]->inh)
{
foreach(lc, root->append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
RelOptInfo *childrel;
if (appinfo->parent_relid != rti)
continue;
childrel = root->simple_rel_array[appinfo->child_relid];
Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
Assert(childrel->direct_lateral_relids == NULL);
childrel->direct_lateral_relids = brel->direct_lateral_relids;
Assert(childrel->lateral_relids == NULL);
childrel->lateral_relids = brel->lateral_relids;
Assert(childrel->lateral_referencers == NULL);
childrel->lateral_referencers = brel->lateral_referencers;
}
}
}
}
/*****************************************************************************
*
* JOIN TREE PROCESSING
*
*****************************************************************************/
/*
* deconstruct_jointree
* Recursively scan the query's join tree for WHERE and JOIN/ON qual
* clauses, and add these to the appropriate restrictinfo and joininfo
* lists belonging to base RelOptInfos. Also, add SpecialJoinInfo nodes
* to root->join_info_list for any outer joins appearing in the query tree.
* Return a "joinlist" data structure showing the join order decisions
* that need to be made by make_one_rel().
*
* The "joinlist" result is a list of items that are either RangeTblRef
* jointree nodes or sub-joinlists. All the items at the same level of
* joinlist must be joined in an order to be determined by make_one_rel()
* (note that legal orders may be constrained by SpecialJoinInfo nodes).
* A sub-joinlist represents a subproblem to be planned separately. Currently
* sub-joinlists arise only from FULL OUTER JOIN or when collapsing of
* subproblems is stopped by join_collapse_limit or from_collapse_limit.
*
* NOTE: when dealing with inner joins, it is appropriate to let a qual clause
* be evaluated at the lowest level where all the variables it mentions are
* available. However, we cannot push a qual down into the nullable side(s)
* of an outer join since the qual might eliminate matching rows and cause a
* NULL row to be incorrectly emitted by the join. Therefore, we artificially
* OR the minimum-relids of such an outer join into the required_relids of
* clauses appearing above it. This forces those clauses to be delayed until
* application of the outer join (or maybe even higher in the join tree).
*/
List *
deconstruct_jointree(PlannerInfo *root)
{
List *result;
Relids qualscope;
Relids inner_join_rels;
List *postponed_qual_list = NIL;
/* Start recursion at top of jointree */
Assert(root->parse->jointree != NULL &&
IsA(root->parse->jointree, FromExpr));
/* this is filled as we scan the jointree */
root->nullable_baserels = NULL;
result = deconstruct_recurse(root, (Node *) root->parse->jointree, false,
&qualscope, &inner_join_rels,
&postponed_qual_list);
/* Shouldn't be any leftover quals */
Assert(postponed_qual_list == NIL);
return result;
}
/*
* deconstruct_recurse
* One recursion level of deconstruct_jointree processing.
*
* Inputs:
* jtnode is the jointree node to examine
* below_outer_join is TRUE if this node is within the nullable side of a
* higher-level outer join
* Outputs:
* *qualscope gets the set of base Relids syntactically included in this
* jointree node (do not modify or free this, as it may also be pointed
* to by RestrictInfo and SpecialJoinInfo nodes)
* *inner_join_rels gets the set of base Relids syntactically included in
* inner joins appearing at or below this jointree node (do not modify
* or free this, either)
* *postponed_qual_list is a list of PostponedQual structs, which we can
* add quals to if they turn out to belong to a higher join level
* Return value is the appropriate joinlist for this jointree node
*
* In addition, entries will be added to root->join_info_list for outer joins.
*/
static List *
deconstruct_recurse(PlannerInfo *root, Node *jtnode, bool below_outer_join,
Relids *qualscope, Relids *inner_join_rels,
List **postponed_qual_list)
{
List *joinlist;
if (jtnode == NULL)
{
*qualscope = NULL;
*inner_join_rels = NULL;
return NIL;
}
if (IsA(jtnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jtnode)->rtindex;
/* No quals to deal with, just return correct result */
*qualscope = bms_make_singleton(varno);
/* A single baserel does not create an inner join */
*inner_join_rels = NULL;
joinlist = list_make1(jtnode);
}
else if (IsA(jtnode, FromExpr))
{
FromExpr *f = (FromExpr *) jtnode;
List *child_postponed_quals = NIL;
int remaining;
ListCell *l;
/*
* First, recurse to handle child joins. We collapse subproblems into
* a single joinlist whenever the resulting joinlist wouldn't exceed
* from_collapse_limit members. Also, always collapse one-element
* subproblems, since that won't lengthen the joinlist anyway.
*/
*qualscope = NULL;
*inner_join_rels = NULL;
joinlist = NIL;
remaining = list_length(f->fromlist);
foreach(l, f->fromlist)
{
Relids sub_qualscope;
List *sub_joinlist;
int sub_members;
sub_joinlist = deconstruct_recurse(root, lfirst(l),
below_outer_join,
&sub_qualscope,
inner_join_rels,
&child_postponed_quals);
*qualscope = bms_add_members(*qualscope, sub_qualscope);
sub_members = list_length(sub_joinlist);
remaining--;
if (sub_members <= 1 ||
list_length(joinlist) + sub_members + remaining <= from_collapse_limit)
joinlist = list_concat(joinlist, sub_joinlist);
else
joinlist = lappend(joinlist, sub_joinlist);
}
/*
* A FROM with more than one list element is an inner join subsuming
* all below it, so we should report inner_join_rels = qualscope. If
* there was exactly one element, we should (and already did) report
* whatever its inner_join_rels were. If there were no elements (is
* that possible?) the initialization before the loop fixed it.
*/
if (list_length(f->fromlist) > 1)
*inner_join_rels = *qualscope;
/*
* Try to process any quals postponed by children. If they need
* further postponement, add them to my output postponed_qual_list.
*/
foreach(l, child_postponed_quals)
{
PostponedQual *pq = (PostponedQual *) lfirst(l);
if (bms_is_subset(pq->relids, *qualscope))
distribute_qual_to_rels(root, pq->qual,
false, below_outer_join, JOIN_INNER,
*qualscope, NULL, NULL, NULL,
NULL);
else
*postponed_qual_list = lappend(*postponed_qual_list, pq);
}
/*
* Now process the top-level quals.
*/
foreach(l, (List *) f->quals)
{
Node *qual = (Node *) lfirst(l);
distribute_qual_to_rels(root, qual,
false, below_outer_join, JOIN_INNER,
*qualscope, NULL, NULL, NULL,
postponed_qual_list);
}
}
else if (IsA(jtnode, JoinExpr))
{
JoinExpr *j = (JoinExpr *) jtnode;
List *child_postponed_quals = NIL;
Relids leftids,
rightids,
left_inners,
right_inners,
nonnullable_rels,
nullable_rels,
ojscope;
List *leftjoinlist,
*rightjoinlist;
List *my_quals;
SpecialJoinInfo *sjinfo;
ListCell *l;
/*
* Order of operations here is subtle and critical. First we recurse
* to handle sub-JOINs. Their join quals will be placed without
* regard for whether this level is an outer join, which is correct.
* Then we place our own join quals, which are restricted by lower
* outer joins in any case, and are forced to this level if this is an
* outer join and they mention the outer side. Finally, if this is an
* outer join, we create a join_info_list entry for the join. This
* will prevent quals above us in the join tree that use those rels
* from being pushed down below this level. (It's okay for upper
* quals to be pushed down to the outer side, however.)
*/
switch (j->jointype)
{
case JOIN_INNER:
leftjoinlist = deconstruct_recurse(root, j->larg,
below_outer_join,
&leftids, &left_inners,
&child_postponed_quals);
rightjoinlist = deconstruct_recurse(root, j->rarg,
below_outer_join,
&rightids, &right_inners,
&child_postponed_quals);
*qualscope = bms_union(leftids, rightids);
*inner_join_rels = *qualscope;
/* Inner join adds no restrictions for quals */
nonnullable_rels = NULL;
/* and it doesn't force anything to null, either */
nullable_rels = NULL;
break;
case JOIN_LEFT:
case JOIN_ANTI:
leftjoinlist = deconstruct_recurse(root, j->larg,
below_outer_join,
&leftids, &left_inners,
&child_postponed_quals);
rightjoinlist = deconstruct_recurse(root, j->rarg,
true,
&rightids, &right_inners,
&child_postponed_quals);
*qualscope = bms_union(leftids, rightids);
*inner_join_rels = bms_union(left_inners, right_inners);
nonnullable_rels = leftids;
nullable_rels = rightids;
break;
case JOIN_SEMI:
leftjoinlist = deconstruct_recurse(root, j->larg,
below_outer_join,
&leftids, &left_inners,
&child_postponed_quals);
rightjoinlist = deconstruct_recurse(root, j->rarg,
below_outer_join,
&rightids, &right_inners,
&child_postponed_quals);
*qualscope = bms_union(leftids, rightids);
*inner_join_rels = bms_union(left_inners, right_inners);
/* Semi join adds no restrictions for quals */
nonnullable_rels = NULL;
/*
* Theoretically, a semijoin would null the RHS; but since the
* RHS can't be accessed above the join, this is immaterial
* and we needn't account for it.
*/
nullable_rels = NULL;
break;
case JOIN_FULL:
leftjoinlist = deconstruct_recurse(root, j->larg,
true,
&leftids, &left_inners,
&child_postponed_quals);
rightjoinlist = deconstruct_recurse(root, j->rarg,
true,
&rightids, &right_inners,
&child_postponed_quals);
*qualscope = bms_union(leftids, rightids);
*inner_join_rels = bms_union(left_inners, right_inners);
/* each side is both outer and inner */
nonnullable_rels = *qualscope;
nullable_rels = *qualscope;
break;
default:
/* JOIN_RIGHT was eliminated during reduce_outer_joins() */
elog(ERROR, "unrecognized join type: %d",
(int) j->jointype);
nonnullable_rels = NULL; /* keep compiler quiet */
nullable_rels = NULL;
leftjoinlist = rightjoinlist = NIL;
break;
}
/* Report all rels that will be nulled anywhere in the jointree */
root->nullable_baserels = bms_add_members(root->nullable_baserels,
nullable_rels);
/*
* Try to process any quals postponed by children. If they need
* further postponement, add them to my output postponed_qual_list.
* Quals that can be processed now must be included in my_quals, so
* that they'll be handled properly in make_outerjoininfo.
*/
my_quals = NIL;
foreach(l, child_postponed_quals)
{
PostponedQual *pq = (PostponedQual *) lfirst(l);
if (bms_is_subset(pq->relids, *qualscope))
my_quals = lappend(my_quals, pq->qual);
else
{
/*
* We should not be postponing any quals past an outer join.
* If this Assert fires, pull_up_subqueries() messed up.
*/
Assert(j->jointype == JOIN_INNER);
*postponed_qual_list = lappend(*postponed_qual_list, pq);
}
}
/* list_concat is nondestructive of its second argument */
my_quals = list_concat(my_quals, (List *) j->quals);
/*
* For an OJ, form the SpecialJoinInfo now, because we need the OJ's
* semantic scope (ojscope) to pass to distribute_qual_to_rels. But
* we mustn't add it to join_info_list just yet, because we don't want
* distribute_qual_to_rels to think it is an outer join below us.
*
* Semijoins are a bit of a hybrid: we build a SpecialJoinInfo, but we
* want ojscope = NULL for distribute_qual_to_rels.
*/
if (j->jointype != JOIN_INNER)
{
sjinfo = make_outerjoininfo(root,
leftids, rightids,
*inner_join_rels,
j->jointype,
my_quals);
if (j->jointype == JOIN_SEMI)
ojscope = NULL;
else
ojscope = bms_union(sjinfo->min_lefthand,
sjinfo->min_righthand);
}
else
{
sjinfo = NULL;
ojscope = NULL;
}
/* Process the JOIN's qual clauses */
foreach(l, my_quals)
{
Node *qual = (Node *) lfirst(l);
distribute_qual_to_rels(root, qual,
false, below_outer_join, j->jointype,
*qualscope,
ojscope, nonnullable_rels, NULL,
postponed_qual_list);
}
/* Now we can add the SpecialJoinInfo to join_info_list */
if (sjinfo)
{
root->join_info_list = lappend(root->join_info_list, sjinfo);
/* Each time we do that, recheck placeholder eval levels */
update_placeholder_eval_levels(root, sjinfo);
}
/*
* Finally, compute the output joinlist. We fold subproblems together
* except at a FULL JOIN or where join_collapse_limit would be
* exceeded.
*/
if (j->jointype == JOIN_FULL)
{
/* force the join order exactly at this node */
joinlist = list_make1(list_make2(leftjoinlist, rightjoinlist));
}
else if (list_length(leftjoinlist) + list_length(rightjoinlist) <=
join_collapse_limit)
{
/* OK to combine subproblems */
joinlist = list_concat(leftjoinlist, rightjoinlist);
}
else
{
/* can't combine, but needn't force join order above here */
Node *leftpart,
*rightpart;
/* avoid creating useless 1-element sublists */
if (list_length(leftjoinlist) == 1)
leftpart = (Node *) linitial(leftjoinlist);
else
leftpart = (Node *) leftjoinlist;
if (list_length(rightjoinlist) == 1)
rightpart = (Node *) linitial(rightjoinlist);
else
rightpart = (Node *) rightjoinlist;
joinlist = list_make2(leftpart, rightpart);
}
}
else
{
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(jtnode));
joinlist = NIL; /* keep compiler quiet */
}
return joinlist;
}
/*
* make_outerjoininfo
* Build a SpecialJoinInfo for the current outer join
*
* Inputs:
* left_rels: the base Relids syntactically on outer side of join
* right_rels: the base Relids syntactically on inner side of join
* inner_join_rels: base Relids participating in inner joins below this one
* jointype: what it says (must always be LEFT, FULL, SEMI, or ANTI)
* clause: the outer join's join condition (in implicit-AND format)
*
* The node should eventually be appended to root->join_info_list, but we
* do not do that here.
*
* Note: we assume that this function is invoked bottom-up, so that
* root->join_info_list already contains entries for all outer joins that are
* syntactically below this one.
*/
static SpecialJoinInfo *
make_outerjoininfo(PlannerInfo *root,
Relids left_rels, Relids right_rels,
Relids inner_join_rels,
JoinType jointype, List *clause)
{
SpecialJoinInfo *sjinfo = makeNode(SpecialJoinInfo);
Relids clause_relids;
Relids strict_relids;
Relids min_lefthand;
Relids min_righthand;
ListCell *l;
/*
* We should not see RIGHT JOIN here because left/right were switched
* earlier
*/
Assert(jointype != JOIN_INNER);
Assert(jointype != JOIN_RIGHT);
/*
* Presently the executor cannot support FOR [KEY] UPDATE/SHARE marking of
* rels appearing on the nullable side of an outer join. (It's somewhat
* unclear what that would mean, anyway: what should we mark when a result
* row is generated from no element of the nullable relation?) So,
* complain if any nullable rel is FOR [KEY] UPDATE/SHARE.
*
* You might be wondering why this test isn't made far upstream in the
* parser. It's because the parser hasn't got enough info --- consider
* FOR UPDATE applied to a view. Only after rewriting and flattening do
* we know whether the view contains an outer join.
*
* We use the original RowMarkClause list here; the PlanRowMark list would
* list everything.
*/
foreach(l, root->parse->rowMarks)
{
RowMarkClause *rc = (RowMarkClause *) lfirst(l);
if (bms_is_member(rc->rti, right_rels) ||
(jointype == JOIN_FULL && bms_is_member(rc->rti, left_rels)))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
/*------
translator: %s is a SQL row locking clause such as FOR UPDATE */
errmsg("%s cannot be applied to the nullable side of an outer join",
LCS_asString(rc->strength))));
}
sjinfo->syn_lefthand = left_rels;
sjinfo->syn_righthand = right_rels;
sjinfo->jointype = jointype;
/* this always starts out false */
sjinfo->delay_upper_joins = false;
compute_semijoin_info(sjinfo, clause);
/* If it's a full join, no need to be very smart */
if (jointype == JOIN_FULL)
{
sjinfo->min_lefthand = bms_copy(left_rels);
sjinfo->min_righthand = bms_copy(right_rels);
sjinfo->lhs_strict = false; /* don't care about this */
return sjinfo;
}
/*
* Retrieve all relids mentioned within the join clause.
*/
clause_relids = pull_varnos((Node *) clause);
/*
* For which relids is the clause strict, ie, it cannot succeed if the
* rel's columns are all NULL?
*/
strict_relids = find_nonnullable_rels((Node *) clause);
/* Remember whether the clause is strict for any LHS relations */
sjinfo->lhs_strict = bms_overlap(strict_relids, left_rels);
/*
* Required LHS always includes the LHS rels mentioned in the clause. We
* may have to add more rels based on lower outer joins; see below.
*/
min_lefthand = bms_intersect(clause_relids, left_rels);
/*
* Similarly for required RHS. But here, we must also include any lower
* inner joins, to ensure we don't try to commute with any of them.
*/
min_righthand = bms_int_members(bms_union(clause_relids, inner_join_rels),
right_rels);
/*
* Now check previous outer joins for ordering restrictions.
*/
foreach(l, root->join_info_list)
{
SpecialJoinInfo *otherinfo = (SpecialJoinInfo *) lfirst(l);
/* ignore full joins --- other mechanisms preserve their ordering */
if (otherinfo->jointype == JOIN_FULL)
continue;
/*
* For a lower OJ in our LHS, if our join condition uses the lower
* join's RHS and is not strict for that rel, we must preserve the
* ordering of the two OJs, so add lower OJ's full syntactic relset to
* min_lefthand. (We must use its full syntactic relset, not just its
* min_lefthand + min_righthand. This is because there might be other
* OJs below this one that this one can commute with, but we cannot
* commute with them if we don't with this one.) Also, if the current
* join is a semijoin or antijoin, we must preserve ordering
* regardless of strictness.
*
* Note: I believe we have to insist on being strict for at least one
* rel in the lower OJ's min_righthand, not its whole syn_righthand.
*/
if (bms_overlap(left_rels, otherinfo->syn_righthand))
{
if (bms_overlap(clause_relids, otherinfo->syn_righthand) &&
(jointype == JOIN_SEMI || jointype == JOIN_ANTI ||
!bms_overlap(strict_relids, otherinfo->min_righthand)))
{
min_lefthand = bms_add_members(min_lefthand,
otherinfo->syn_lefthand);
min_lefthand = bms_add_members(min_lefthand,
otherinfo->syn_righthand);
}
}
/*
* For a lower OJ in our RHS, if our join condition does not use the
* lower join's RHS and the lower OJ's join condition is strict, we
* can interchange the ordering of the two OJs; otherwise we must add
* the lower OJ's full syntactic relset to min_righthand.
*
* Also, if our join condition does not use the lower join's LHS
* either, force the ordering to be preserved. Otherwise we can end
* up with SpecialJoinInfos with identical min_righthands, which can
* confuse join_is_legal (see discussion in backend/optimizer/README).
*
* Also, we must preserve ordering anyway if either the current join
* or the lower OJ is either a semijoin or an antijoin.
*
* Here, we have to consider that "our join condition" includes any
* clauses that syntactically appeared above the lower OJ and below
* ours; those are equivalent to degenerate clauses in our OJ and must
* be treated as such. Such clauses obviously can't reference our
* LHS, and they must be non-strict for the lower OJ's RHS (else
* reduce_outer_joins would have reduced the lower OJ to a plain
* join). Hence the other ways in which we handle clauses within our
* join condition are not affected by them. The net effect is
* therefore sufficiently represented by the delay_upper_joins flag
* saved for us by check_outerjoin_delay.
*/
if (bms_overlap(right_rels, otherinfo->syn_righthand))
{
if (bms_overlap(clause_relids, otherinfo->syn_righthand) ||
!bms_overlap(clause_relids, otherinfo->min_lefthand) ||
jointype == JOIN_SEMI ||
jointype == JOIN_ANTI ||
otherinfo->jointype == JOIN_SEMI ||
otherinfo->jointype == JOIN_ANTI ||
!otherinfo->lhs_strict || otherinfo->delay_upper_joins)
{
min_righthand = bms_add_members(min_righthand,
otherinfo->syn_lefthand);
min_righthand = bms_add_members(min_righthand,
otherinfo->syn_righthand);
}
}
}
/*
* Examine PlaceHolderVars. If a PHV is supposed to be evaluated within
* this join's nullable side, then ensure that min_righthand contains the
* full eval_at set of the PHV. This ensures that the PHV actually can be
* evaluated within the RHS. Note that this works only because we should
* already have determined the final eval_at level for any PHV
* syntactically within this join.
*/
foreach(l, root->placeholder_list)
{
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
Relids ph_syn_level = phinfo->ph_var->phrels;
/* Ignore placeholder if it didn't syntactically come from RHS */
if (!bms_is_subset(ph_syn_level, right_rels))
continue;
/* Else, prevent join from being formed before we eval the PHV */
min_righthand = bms_add_members(min_righthand, phinfo->ph_eval_at);
}
/*
* If we found nothing to put in min_lefthand, punt and make it the full
* LHS, to avoid having an empty min_lefthand which will confuse later
* processing. (We don't try to be smart about such cases, just correct.)
* Likewise for min_righthand.
*/
if (bms_is_empty(min_lefthand))
min_lefthand = bms_copy(left_rels);
if (bms_is_empty(min_righthand))
min_righthand = bms_copy(right_rels);
/* Now they'd better be nonempty */
Assert(!bms_is_empty(min_lefthand));
Assert(!bms_is_empty(min_righthand));
/* Shouldn't overlap either */
Assert(!bms_overlap(min_lefthand, min_righthand));
sjinfo->min_lefthand = min_lefthand;
sjinfo->min_righthand = min_righthand;
return sjinfo;
}
/*
* compute_semijoin_info
* Fill semijoin-related fields of a new SpecialJoinInfo
*
* Note: this relies on only the jointype and syn_righthand fields of the
* SpecialJoinInfo; the rest may not be set yet.
*/
static void
compute_semijoin_info(SpecialJoinInfo *sjinfo, List *clause)
{
List *semi_operators;
List *semi_rhs_exprs;
bool all_btree;
bool all_hash;
ListCell *lc;
/* Initialize semijoin-related fields in case we can't unique-ify */
sjinfo->semi_can_btree = false;
sjinfo->semi_can_hash = false;
sjinfo->semi_operators = NIL;
sjinfo->semi_rhs_exprs = NIL;
/* Nothing more to do if it's not a semijoin */
if (sjinfo->jointype != JOIN_SEMI)
return;
/*
* Look to see whether the semijoin's join quals consist of AND'ed
* equality operators, with (only) RHS variables on only one side of each
* one. If so, we can figure out how to enforce uniqueness for the RHS.
*
* Note that the input clause list is the list of quals that are
* *syntactically* associated with the semijoin, which in practice means
* the synthesized comparison list for an IN or the WHERE of an EXISTS.
* Particularly in the latter case, it might contain clauses that aren't
* *semantically* associated with the join, but refer to just one side or
* the other. We can ignore such clauses here, as they will just drop
* down to be processed within one side or the other. (It is okay to
* consider only the syntactically-associated clauses here because for a
* semijoin, no higher-level quals could refer to the RHS, and so there
* can be no other quals that are semantically associated with this join.
* We do things this way because it is useful to have the set of potential
* unique-ification expressions before we can extract the list of quals
* that are actually semantically associated with the particular join.)
*
* Note that the semi_operators list consists of the joinqual operators
* themselves (but commuted if needed to put the RHS value on the right).
* These could be cross-type operators, in which case the operator
* actually needed for uniqueness is a related single-type operator. We
* assume here that that operator will be available from the btree or hash
* opclass when the time comes ... if not, create_unique_plan() will fail.
*/
semi_operators = NIL;
semi_rhs_exprs = NIL;
all_btree = true;
all_hash = enable_hashagg; /* don't consider hash if not enabled */
foreach(lc, clause)
{
OpExpr *op = (OpExpr *) lfirst(lc);
Oid opno;
Node *left_expr;
Node *right_expr;
Relids left_varnos;
Relids right_varnos;
Relids all_varnos;
Oid opinputtype;
/* Is it a binary opclause? */
if (!IsA(op, OpExpr) ||
list_length(op->args) != 2)
{
/* No, but does it reference both sides? */
all_varnos = pull_varnos((Node *) op);
if (!bms_overlap(all_varnos, sjinfo->syn_righthand) ||
bms_is_subset(all_varnos, sjinfo->syn_righthand))
{
/*
* Clause refers to only one rel, so ignore it --- unless it
* contains volatile functions, in which case we'd better
* punt.
*/
if (contain_volatile_functions((Node *) op))
return;
continue;
}
/* Non-operator clause referencing both sides, must punt */
return;
}
/* Extract data from binary opclause */
opno = op->opno;
left_expr = linitial(op->args);
right_expr = lsecond(op->args);
left_varnos = pull_varnos(left_expr);
right_varnos = pull_varnos(right_expr);
all_varnos = bms_union(left_varnos, right_varnos);
opinputtype = exprType(left_expr);
/* Does it reference both sides? */
if (!bms_overlap(all_varnos, sjinfo->syn_righthand) ||
bms_is_subset(all_varnos, sjinfo->syn_righthand))
{
/*
* Clause refers to only one rel, so ignore it --- unless it
* contains volatile functions, in which case we'd better punt.
*/
if (contain_volatile_functions((Node *) op))
return;
continue;
}
/* check rel membership of arguments */
if (!bms_is_empty(right_varnos) &&
bms_is_subset(right_varnos, sjinfo->syn_righthand) &&
!bms_overlap(left_varnos, sjinfo->syn_righthand))
{
/* typical case, right_expr is RHS variable */
}
else if (!bms_is_empty(left_varnos) &&
bms_is_subset(left_varnos, sjinfo->syn_righthand) &&
!bms_overlap(right_varnos, sjinfo->syn_righthand))
{
/* flipped case, left_expr is RHS variable */
opno = get_commutator(opno);
if (!OidIsValid(opno))
return;
right_expr = left_expr;
}
else
{
/* mixed membership of args, punt */
return;
}
/* all operators must be btree equality or hash equality */
if (all_btree)
{
/* oprcanmerge is considered a hint... */
if (!op_mergejoinable(opno, opinputtype) ||
get_mergejoin_opfamilies(opno) == NIL)
all_btree = false;
}
if (all_hash)
{
/* ... but oprcanhash had better be correct */
if (!op_hashjoinable(opno, opinputtype))
all_hash = false;
}
if (!(all_btree || all_hash))
return;
/* so far so good, keep building lists */
semi_operators = lappend_oid(semi_operators, opno);
semi_rhs_exprs = lappend(semi_rhs_exprs, copyObject(right_expr));
}
/* Punt if we didn't find at least one column to unique-ify */
if (semi_rhs_exprs == NIL)
return;
/*
* The expressions we'd need to unique-ify mustn't be volatile.
*/
if (contain_volatile_functions((Node *) semi_rhs_exprs))
return;
/*
* If we get here, we can unique-ify the semijoin's RHS using at least one
* of sorting and hashing. Save the information about how to do that.
*/
sjinfo->semi_can_btree = all_btree;
sjinfo->semi_can_hash = all_hash;
sjinfo->semi_operators = semi_operators;
sjinfo->semi_rhs_exprs = semi_rhs_exprs;
}
/*****************************************************************************
*
* QUALIFICATIONS
*
*****************************************************************************/
/*
* distribute_qual_to_rels
* Add clause information to either the baserestrictinfo or joininfo list
* (depending on whether the clause is a join) of each base relation
* mentioned in the clause. A RestrictInfo node is created and added to
* the appropriate list for each rel. Alternatively, if the clause uses a
* mergejoinable operator and is not delayed by outer-join rules, enter
* the left- and right-side expressions into the query's list of
* EquivalenceClasses. Alternatively, if the clause needs to be treated
* as belonging to a higher join level, just add it to postponed_qual_list.
*
* 'clause': the qual clause to be distributed
* 'is_deduced': TRUE if the qual came from implied-equality deduction
* 'below_outer_join': TRUE if the qual is from a JOIN/ON that is below the
* nullable side of a higher-level outer join
* 'jointype': type of join the qual is from (JOIN_INNER for a WHERE clause)
* 'qualscope': set of baserels the qual's syntactic scope covers
* 'ojscope': NULL if not an outer-join qual, else the minimum set of baserels
* needed to form this join
* 'outerjoin_nonnullable': NULL if not an outer-join qual, else the set of
* baserels appearing on the outer (nonnullable) side of the join
* (for FULL JOIN this includes both sides of the join, and must in fact
* equal qualscope)
* 'deduced_nullable_relids': if is_deduced is TRUE, the nullable relids to
* impute to the clause; otherwise NULL
* 'postponed_qual_list': list of PostponedQual structs, which we can add
* this qual to if it turns out to belong to a higher join level.
* Can be NULL if caller knows postponement is impossible.
*
* 'qualscope' identifies what level of JOIN the qual came from syntactically.
* 'ojscope' is needed if we decide to force the qual up to the outer-join
* level, which will be ojscope not necessarily qualscope.
*
* In normal use (when is_deduced is FALSE), at the time this is called,
* root->join_info_list must contain entries for all and only those special
* joins that are syntactically below this qual. But when is_deduced is TRUE,
* we are adding new deduced clauses after completion of deconstruct_jointree,
* so it cannot be assumed that root->join_info_list has anything to do with
* qual placement.
*/
static void
distribute_qual_to_rels(PlannerInfo *root, Node *clause,
bool is_deduced,
bool below_outer_join,
JoinType jointype,
Relids qualscope,
Relids ojscope,
Relids outerjoin_nonnullable,
Relids deduced_nullable_relids,
List **postponed_qual_list)
{
Relids relids;
bool is_pushed_down;
bool outerjoin_delayed;
bool pseudoconstant = false;
bool maybe_equivalence;
bool maybe_outer_join;
Relids nullable_relids;
RestrictInfo *restrictinfo;
/*
* Retrieve all relids mentioned within the clause.
*/
relids = pull_varnos(clause);
/*
* In ordinary SQL, a WHERE or JOIN/ON clause can't reference any rels
* that aren't within its syntactic scope; however, if we pulled up a
* LATERAL subquery then we might find such references in quals that have
* been pulled up. We need to treat such quals as belonging to the join
* level that includes every rel they reference. Although we could make
* pull_up_subqueries() place such quals correctly to begin with, it's
* easier to handle it here. When we find a clause that contains Vars
* outside its syntactic scope, we add it to the postponed-quals list, and
* process it once we've recursed back up to the appropriate join level.
*/
if (!bms_is_subset(relids, qualscope))
{
PostponedQual *pq = (PostponedQual *) palloc(sizeof(PostponedQual));
Assert(root->hasLateralRTEs); /* shouldn't happen otherwise */
Assert(jointype == JOIN_INNER); /* mustn't postpone past outer join */
Assert(!is_deduced); /* shouldn't be deduced, either */
pq->qual = clause;
pq->relids = relids;
*postponed_qual_list = lappend(*postponed_qual_list, pq);
return;
}
/*
* If it's an outer-join clause, also check that relids is a subset of
* ojscope. (This should not fail if the syntactic scope check passed.)
*/
if (ojscope && !bms_is_subset(relids, ojscope))
elog(ERROR, "JOIN qualification cannot refer to other relations");
/*
* If the clause is variable-free, our normal heuristic for pushing it
* down to just the mentioned rels doesn't work, because there are none.
*
* If the clause is an outer-join clause, we must force it to the OJ's
* semantic level to preserve semantics.
*
* Otherwise, when the clause contains volatile functions, we force it to
* be evaluated at its original syntactic level. This preserves the
* expected semantics.
*
* When the clause contains no volatile functions either, it is actually a
* pseudoconstant clause that will not change value during any one
* execution of the plan, and hence can be used as a one-time qual in a
* gating Result plan node. We put such a clause into the regular
* RestrictInfo lists for the moment, but eventually createplan.c will
* pull it out and make a gating Result node immediately above whatever
* plan node the pseudoconstant clause is assigned to. It's usually best
* to put a gating node as high in the plan tree as possible. If we are
* not below an outer join, we can actually push the pseudoconstant qual
* all the way to the top of the tree. If we are below an outer join, we
* leave the qual at its original syntactic level (we could push it up to
* just below the outer join, but that seems more complex than it's
* worth).
*/
if (bms_is_empty(relids))
{
if (ojscope)
{
/* clause is attached to outer join, eval it there */
relids = bms_copy(ojscope);
/* mustn't use as gating qual, so don't mark pseudoconstant */
}
else
{
/* eval at original syntactic level */
relids = bms_copy(qualscope);
if (!contain_volatile_functions(clause))
{
/* mark as gating qual */
pseudoconstant = true;
/* tell createplan.c to check for gating quals */
root->hasPseudoConstantQuals = true;
/* if not below outer join, push it to top of tree */
if (!below_outer_join)
{
relids =
get_relids_in_jointree((Node *) root->parse->jointree,
false);
qualscope = bms_copy(relids);
}
}
}
}
/*----------
* Check to see if clause application must be delayed by outer-join
* considerations.
*
* A word about is_pushed_down: we mark the qual as "pushed down" if
* it is (potentially) applicable at a level different from its original
* syntactic level. This flag is used to distinguish OUTER JOIN ON quals
* from other quals pushed down to the same joinrel. The rules are:
* WHERE quals and INNER JOIN quals: is_pushed_down = true.
* Non-degenerate OUTER JOIN quals: is_pushed_down = false.
* Degenerate OUTER JOIN quals: is_pushed_down = true.
* A "degenerate" OUTER JOIN qual is one that doesn't mention the
* non-nullable side, and hence can be pushed down into the nullable side
* without changing the join result. It is correct to treat it as a
* regular filter condition at the level where it is evaluated.
*
* Note: it is not immediately obvious that a simple boolean is enough
* for this: if for some reason we were to attach a degenerate qual to
* its original join level, it would need to be treated as an outer join
* qual there. However, this cannot happen, because all the rels the
* clause mentions must be in the outer join's min_righthand, therefore
* the join it needs must be formed before the outer join; and we always
* attach quals to the lowest level where they can be evaluated. But
* if we were ever to re-introduce a mechanism for delaying evaluation
* of "expensive" quals, this area would need work.
*----------
*/
if (is_deduced)
{
/*
* If the qual came from implied-equality deduction, it should not be
* outerjoin-delayed, else deducer blew it. But we can't check this
* because the join_info_list may now contain OJs above where the qual
* belongs. For the same reason, we must rely on caller to supply the
* correct nullable_relids set.
*/
Assert(!ojscope);
is_pushed_down = true;
outerjoin_delayed = false;
nullable_relids = deduced_nullable_relids;
/* Don't feed it back for more deductions */
maybe_equivalence = false;
maybe_outer_join = false;
}
else if (bms_overlap(relids, outerjoin_nonnullable))
{
/*
* The qual is attached to an outer join and mentions (some of the)
* rels on the nonnullable side, so it's not degenerate.
*
* We can't use such a clause to deduce equivalence (the left and
* right sides might be unequal above the join because one of them has
* gone to NULL) ... but we might be able to use it for more limited
* deductions, if it is mergejoinable. So consider adding it to the
* lists of set-aside outer-join clauses.
*/
is_pushed_down = false;
maybe_equivalence = false;
maybe_outer_join = true;
/* Check to see if must be delayed by lower outer join */
outerjoin_delayed = check_outerjoin_delay(root,
&relids,
&nullable_relids,
false);
/*
* Now force the qual to be evaluated exactly at the level of joining
* corresponding to the outer join. We cannot let it get pushed down
* into the nonnullable side, since then we'd produce no output rows,
* rather than the intended single null-extended row, for any
* nonnullable-side rows failing the qual.
*
* (Do this step after calling check_outerjoin_delay, because that
* trashes relids.)
*/
Assert(ojscope);
relids = ojscope;
Assert(!pseudoconstant);
}
else
{
/*
* Normal qual clause or degenerate outer-join clause. Either way, we
* can mark it as pushed-down.
*/
is_pushed_down = true;
/* Check to see if must be delayed by lower outer join */
outerjoin_delayed = check_outerjoin_delay(root,
&relids,
&nullable_relids,
true);
if (outerjoin_delayed)
{
/* Should still be a subset of current scope ... */
Assert(root->hasLateralRTEs || bms_is_subset(relids, qualscope));
Assert(ojscope == NULL || bms_is_subset(relids, ojscope));
/*
* Because application of the qual will be delayed by outer join,
* we mustn't assume its vars are equal everywhere.
*/
maybe_equivalence = false;
/*
* It's possible that this is an IS NULL clause that's redundant
* with a lower antijoin; if so we can just discard it. We need
* not test in any of the other cases, because this will only be
* possible for pushed-down, delayed clauses.
*/
if (check_redundant_nullability_qual(root, clause))
return;
}
else
{
/*
* Qual is not delayed by any lower outer-join restriction, so we
* can consider feeding it to the equivalence machinery. However,
* if it's itself within an outer-join clause, treat it as though
* it appeared below that outer join (note that we can only get
* here when the clause references only nullable-side rels).
*/
maybe_equivalence = true;
if (outerjoin_nonnullable != NULL)
below_outer_join = true;
}
/*
* Since it doesn't mention the LHS, it's certainly not useful as a
* set-aside OJ clause, even if it's in an OJ.
*/
maybe_outer_join = false;
}
/*
* Build the RestrictInfo node itself.
*/
restrictinfo = make_restrictinfo((Expr *) clause,
is_pushed_down,
outerjoin_delayed,
pseudoconstant,
relids,
outerjoin_nonnullable,
nullable_relids);
/*
* If it's a join clause (either naturally, or because delayed by
* outer-join rules), add vars used in the clause to targetlists of their
* relations, so that they will be emitted by the plan nodes that scan
* those relations (else they won't be available at the join node!).
*
* Note: if the clause gets absorbed into an EquivalenceClass then this
* may be unnecessary, but for now we have to do it to cover the case
* where the EC becomes ec_broken and we end up reinserting the original
* clauses into the plan.
*/
if (bms_membership(relids) == BMS_MULTIPLE)
{
List *vars = pull_var_clause(clause,
PVC_RECURSE_AGGREGATES |
PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, relids, false);
list_free(vars);
}
/*
* We check "mergejoinability" of every clause, not only join clauses,
* because we want to know about equivalences between vars of the same
* relation, or between vars and consts.
*/
check_mergejoinable(restrictinfo);
/*
* If it is a true equivalence clause, send it to the EquivalenceClass
* machinery. We do *not* attach it directly to any restriction or join
* lists. The EC code will propagate it to the appropriate places later.
*
* If the clause has a mergejoinable operator and is not
* outerjoin-delayed, yet isn't an equivalence because it is an outer-join
* clause, the EC code may yet be able to do something with it. We add it
* to appropriate lists for further consideration later. Specifically:
*
* If it is a left or right outer-join qualification that relates the two
* sides of the outer join (no funny business like leftvar1 = leftvar2 +
* rightvar), we add it to root->left_join_clauses or
* root->right_join_clauses according to which side the nonnullable
* variable appears on.
*
* If it is a full outer-join qualification, we add it to
* root->full_join_clauses. (Ideally we'd discard cases that aren't
* leftvar = rightvar, as we do for left/right joins, but this routine
* doesn't have the info needed to do that; and the current usage of the
* full_join_clauses list doesn't require that, so it's not currently
* worth complicating this routine's API to make it possible.)
*
* If none of the above hold, pass it off to
* distribute_restrictinfo_to_rels().
*
* In all cases, it's important to initialize the left_ec and right_ec
* fields of a mergejoinable clause, so that all possibly mergejoinable
* expressions have representations in EquivalenceClasses. If
* process_equivalence is successful, it will take care of that;
* otherwise, we have to call initialize_mergeclause_eclasses to do it.
*/
if (restrictinfo->mergeopfamilies)
{
if (maybe_equivalence)
{
if (check_equivalence_delay(root, restrictinfo) &&
process_equivalence(root, restrictinfo, below_outer_join))
return;
/* EC rejected it, so set left_ec/right_ec the hard way ... */
initialize_mergeclause_eclasses(root, restrictinfo);
/* ... and fall through to distribute_restrictinfo_to_rels */
}
else if (maybe_outer_join && restrictinfo->can_join)
{
/* we need to set up left_ec/right_ec the hard way */
initialize_mergeclause_eclasses(root, restrictinfo);
/* now see if it should go to any outer-join lists */
if (bms_is_subset(restrictinfo->left_relids,
outerjoin_nonnullable) &&
!bms_overlap(restrictinfo->right_relids,
outerjoin_nonnullable))
{
/* we have outervar = innervar */
root->left_join_clauses = lappend(root->left_join_clauses,
restrictinfo);
return;
}
if (bms_is_subset(restrictinfo->right_relids,
outerjoin_nonnullable) &&
!bms_overlap(restrictinfo->left_relids,
outerjoin_nonnullable))
{
/* we have innervar = outervar */
root->right_join_clauses = lappend(root->right_join_clauses,
restrictinfo);
return;
}
if (jointype == JOIN_FULL)
{
/* FULL JOIN (above tests cannot match in this case) */
root->full_join_clauses = lappend(root->full_join_clauses,
restrictinfo);
return;
}
/* nope, so fall through to distribute_restrictinfo_to_rels */
}
else
{
/* we still need to set up left_ec/right_ec */
initialize_mergeclause_eclasses(root, restrictinfo);
}
}
/* No EC special case applies, so push it into the clause lists */
distribute_restrictinfo_to_rels(root, restrictinfo);
}
/*
* check_outerjoin_delay
* Detect whether a qual referencing the given relids must be delayed
* in application due to the presence of a lower outer join, and/or
* may force extra delay of higher-level outer joins.
*
* If the qual must be delayed, add relids to *relids_p to reflect the lowest
* safe level for evaluating the qual, and return TRUE. Any extra delay for
* higher-level joins is reflected by setting delay_upper_joins to TRUE in
* SpecialJoinInfo structs. We also compute nullable_relids, the set of
* referenced relids that are nullable by lower outer joins (note that this
* can be nonempty even for a non-delayed qual).
*
* For an is_pushed_down qual, we can evaluate the qual as soon as (1) we have
* all the rels it mentions, and (2) we are at or above any outer joins that
* can null any of these rels and are below the syntactic location of the
* given qual. We must enforce (2) because pushing down such a clause below
* the OJ might cause the OJ to emit null-extended rows that should not have
* been formed, or that should have been rejected by the clause. (This is
* only an issue for non-strict quals, since if we can prove a qual mentioning
* only nullable rels is strict, we'd have reduced the outer join to an inner
* join in reduce_outer_joins().)
*
* To enforce (2), scan the join_info_list and merge the required-relid sets of
* any such OJs into the clause's own reference list. At the time we are
* called, the join_info_list contains only outer joins below this qual. We
* have to repeat the scan until no new relids get added; this ensures that
* the qual is suitably delayed regardless of the order in which OJs get
* executed. As an example, if we have one OJ with LHS=A, RHS=B, and one with
* LHS=B, RHS=C, it is implied that these can be done in either order; if the
* B/C join is done first then the join to A can null C, so a qual actually
* mentioning only C cannot be applied below the join to A.
*
* For a non-pushed-down qual, this isn't going to determine where we place the
* qual, but we need to determine outerjoin_delayed and nullable_relids anyway
* for use later in the planning process.
*
* Lastly, a pushed-down qual that references the nullable side of any current
* join_info_list member and has to be evaluated above that OJ (because its
* required relids overlap the LHS too) causes that OJ's delay_upper_joins
* flag to be set TRUE. This will prevent any higher-level OJs from
* being interchanged with that OJ, which would result in not having any
* correct place to evaluate the qual. (The case we care about here is a
* sub-select WHERE clause within the RHS of some outer join. The WHERE
* clause must effectively be treated as a degenerate clause of that outer
* join's condition. Rather than trying to match such clauses with joins
* directly, we set delay_upper_joins here, and when the upper outer join
* is processed by make_outerjoininfo, it will refrain from allowing the
* two OJs to commute.)
*/
static bool
check_outerjoin_delay(PlannerInfo *root,
Relids *relids_p, /* in/out parameter */
Relids *nullable_relids_p, /* output parameter */
bool is_pushed_down)
{
Relids relids;
Relids nullable_relids;
bool outerjoin_delayed;
bool found_some;
/* fast path if no special joins */
if (root->join_info_list == NIL)
{
*nullable_relids_p = NULL;
return false;
}
/* must copy relids because we need the original value at the end */
relids = bms_copy(*relids_p);
nullable_relids = NULL;
outerjoin_delayed = false;
do
{
ListCell *l;
found_some = false;
foreach(l, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
/* do we reference any nullable rels of this OJ? */
if (bms_overlap(relids, sjinfo->min_righthand) ||
(sjinfo->jointype == JOIN_FULL &&
bms_overlap(relids, sjinfo->min_lefthand)))
{
/* yes; have we included all its rels in relids? */
if (!bms_is_subset(sjinfo->min_lefthand, relids) ||
!bms_is_subset(sjinfo->min_righthand, relids))
{
/* no, so add them in */
relids = bms_add_members(relids, sjinfo->min_lefthand);
relids = bms_add_members(relids, sjinfo->min_righthand);
outerjoin_delayed = true;
/* we'll need another iteration */
found_some = true;
}
/* track all the nullable rels of relevant OJs */
nullable_relids = bms_add_members(nullable_relids,
sjinfo->min_righthand);
if (sjinfo->jointype == JOIN_FULL)
nullable_relids = bms_add_members(nullable_relids,
sjinfo->min_lefthand);
/* set delay_upper_joins if needed */
if (is_pushed_down && sjinfo->jointype != JOIN_FULL &&
bms_overlap(relids, sjinfo->min_lefthand))
sjinfo->delay_upper_joins = true;
}
}
} while (found_some);
/* identify just the actually-referenced nullable rels */
nullable_relids = bms_int_members(nullable_relids, *relids_p);
/* replace *relids_p, and return nullable_relids */
bms_free(*relids_p);
*relids_p = relids;
*nullable_relids_p = nullable_relids;
return outerjoin_delayed;
}
/*
* check_equivalence_delay
* Detect whether a potential equivalence clause is rendered unsafe
* by outer-join-delay considerations. Return TRUE if it's safe.
*
* The initial tests in distribute_qual_to_rels will consider a mergejoinable
* clause to be a potential equivalence clause if it is not outerjoin_delayed.
* But since the point of equivalence processing is that we will recombine the
* two sides of the clause with others, we have to check that each side
* satisfies the not-outerjoin_delayed condition on its own; otherwise it might
* not be safe to evaluate everywhere we could place a derived equivalence
* condition.
*/
static bool
check_equivalence_delay(PlannerInfo *root,
RestrictInfo *restrictinfo)
{
Relids relids;
Relids nullable_relids;
/* fast path if no special joins */
if (root->join_info_list == NIL)
return true;
/* must copy restrictinfo's relids to avoid changing it */
relids = bms_copy(restrictinfo->left_relids);
/* check left side does not need delay */
if (check_outerjoin_delay(root, &relids, &nullable_relids, true))
return false;
/* and similarly for the right side */
relids = bms_copy(restrictinfo->right_relids);
if (check_outerjoin_delay(root, &relids, &nullable_relids, true))
return false;
return true;
}
/*
* check_redundant_nullability_qual
* Check to see if the qual is an IS NULL qual that is redundant with
* a lower JOIN_ANTI join.
*
* We want to suppress redundant IS NULL quals, not so much to save cycles
* as to avoid generating bogus selectivity estimates for them. So if
* redundancy is detected here, distribute_qual_to_rels() just throws away
* the qual.
*/
static bool
check_redundant_nullability_qual(PlannerInfo *root, Node *clause)
{
Var *forced_null_var;
Index forced_null_rel;
ListCell *lc;
/* Check for IS NULL, and identify the Var forced to NULL */
forced_null_var = find_forced_null_var(clause);
if (forced_null_var == NULL)
return false;
forced_null_rel = forced_null_var->varno;
/*
* If the Var comes from the nullable side of a lower antijoin, the IS
* NULL condition is necessarily true.
*/
foreach(lc, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
if (sjinfo->jointype == JOIN_ANTI &&
bms_is_member(forced_null_rel, sjinfo->syn_righthand))
return true;
}
return false;
}
/*
* distribute_restrictinfo_to_rels
* Push a completed RestrictInfo into the proper restriction or join
* clause list(s).
*
* This is the last step of distribute_qual_to_rels() for ordinary qual
* clauses. Clauses that are interesting for equivalence-class processing
* are diverted to the EC machinery, but may ultimately get fed back here.
*/
void
distribute_restrictinfo_to_rels(PlannerInfo *root,
RestrictInfo *restrictinfo)
{
Relids relids = restrictinfo->required_relids;
RelOptInfo *rel;
switch (bms_membership(relids))
{
case BMS_SINGLETON:
/*
* There is only one relation participating in the clause, so it
* is a restriction clause for that relation.
*/
rel = find_base_rel(root, bms_singleton_member(relids));
/* Add clause to rel's restriction list */
rel->baserestrictinfo = lappend(rel->baserestrictinfo,
restrictinfo);
break;
case BMS_MULTIPLE:
/*
* The clause is a join clause, since there is more than one rel
* in its relid set.
*/
/*
* Check for hashjoinable operators. (We don't bother setting the
* hashjoin info except in true join clauses.)
*/
check_hashjoinable(restrictinfo);
/*
* Add clause to the join lists of all the relevant relations.
*/
add_join_clause_to_rels(root, restrictinfo, relids);
break;
default:
/*
* clause references no rels, and therefore we have no place to
* attach it. Shouldn't get here if callers are working properly.
*/
elog(ERROR, "cannot cope with variable-free clause");
break;
}
}
/*
* process_implied_equality
* Create a restrictinfo item that says "item1 op item2", and push it
* into the appropriate lists. (In practice opno is always a btree
* equality operator.)
*
* "qualscope" is the nominal syntactic level to impute to the restrictinfo.
* This must contain at least all the rels used in the expressions, but it
* is used only to set the qual application level when both exprs are
* variable-free. Otherwise the qual is applied at the lowest join level
* that provides all its variables.
*
* "nullable_relids" is the set of relids used in the expressions that are
* potentially nullable below the expressions. (This has to be supplied by
* caller because this function is used after deconstruct_jointree, so we
* don't have knowledge of where the clause items came from.)
*
* "both_const" indicates whether both items are known pseudo-constant;
* in this case it is worth applying eval_const_expressions() in case we
* can produce constant TRUE or constant FALSE. (Otherwise it's not,
* because the expressions went through eval_const_expressions already.)
*
* Note: this function will copy item1 and item2, but it is caller's
* responsibility to make sure that the Relids parameters are fresh copies
* not shared with other uses.
*
* This is currently used only when an EquivalenceClass is found to
* contain pseudoconstants. See path/pathkeys.c for more details.
*/
void
process_implied_equality(PlannerInfo *root,
Oid opno,
Oid collation,
Expr *item1,
Expr *item2,
Relids qualscope,
Relids nullable_relids,
bool below_outer_join,
bool both_const)
{
Expr *clause;
/*
* Build the new clause. Copy to ensure it shares no substructure with
* original (this is necessary in case there are subselects in there...)
*/
clause = make_opclause(opno,
BOOLOID, /* opresulttype */
false, /* opretset */
(Expr *) copyObject(item1),
(Expr *) copyObject(item2),
InvalidOid,
collation);
/* If both constant, try to reduce to a boolean constant. */
if (both_const)
{
clause = (Expr *) eval_const_expressions(root, (Node *) clause);
/* If we produced const TRUE, just drop the clause */
if (clause && IsA(clause, Const))
{
Const *cclause = (Const *) clause;
Assert(cclause->consttype == BOOLOID);
if (!cclause->constisnull && DatumGetBool(cclause->constvalue))
return;
}
}
/*
* Push the new clause into all the appropriate restrictinfo lists.
*/
distribute_qual_to_rels(root, (Node *) clause,
true, below_outer_join, JOIN_INNER,
qualscope, NULL, NULL, nullable_relids,
NULL);
}
/*
* build_implied_join_equality --- build a RestrictInfo for a derived equality
*
* This overlaps the functionality of process_implied_equality(), but we
* must return the RestrictInfo, not push it into the joininfo tree.
*
* Note: this function will copy item1 and item2, but it is caller's
* responsibility to make sure that the Relids parameters are fresh copies
* not shared with other uses.
*
* Note: we do not do initialize_mergeclause_eclasses() here. It is
* caller's responsibility that left_ec/right_ec be set as necessary.
*/
RestrictInfo *
build_implied_join_equality(Oid opno,
Oid collation,
Expr *item1,
Expr *item2,
Relids qualscope,
Relids nullable_relids)
{
RestrictInfo *restrictinfo;
Expr *clause;
/*
* Build the new clause. Copy to ensure it shares no substructure with
* original (this is necessary in case there are subselects in there...)
*/
clause = make_opclause(opno,
BOOLOID, /* opresulttype */
false, /* opretset */
(Expr *) copyObject(item1),
(Expr *) copyObject(item2),
InvalidOid,
collation);
/*
* Build the RestrictInfo node itself.
*/
restrictinfo = make_restrictinfo(clause,
true, /* is_pushed_down */
false, /* outerjoin_delayed */
false, /* pseudoconstant */
qualscope, /* required_relids */
NULL, /* outer_relids */
nullable_relids); /* nullable_relids */
/* Set mergejoinability/hashjoinability flags */
check_mergejoinable(restrictinfo);
check_hashjoinable(restrictinfo);
return restrictinfo;
}
/*****************************************************************************
*
* CHECKS FOR MERGEJOINABLE AND HASHJOINABLE CLAUSES
*
*****************************************************************************/
/*
* check_mergejoinable
* If the restrictinfo's clause is mergejoinable, set the mergejoin
* info fields in the restrictinfo.
*
* Currently, we support mergejoin for binary opclauses where
* the operator is a mergejoinable operator. The arguments can be
* anything --- as long as there are no volatile functions in them.
*/
static void
check_mergejoinable(RestrictInfo *restrictinfo)
{
Expr *clause = restrictinfo->clause;
Oid opno;
Node *leftarg;
if (restrictinfo->pseudoconstant)
return;
if (!is_opclause(clause))
return;
if (list_length(((OpExpr *) clause)->args) != 2)
return;
opno = ((OpExpr *) clause)->opno;
leftarg = linitial(((OpExpr *) clause)->args);
if (op_mergejoinable(opno, exprType(leftarg)) &&
!contain_volatile_functions((Node *) clause))
restrictinfo->mergeopfamilies = get_mergejoin_opfamilies(opno);
/*
* Note: op_mergejoinable is just a hint; if we fail to find the operator
* in any btree opfamilies, mergeopfamilies remains NIL and so the clause
* is not treated as mergejoinable.
*/
}
/*
* check_hashjoinable
* If the restrictinfo's clause is hashjoinable, set the hashjoin
* info fields in the restrictinfo.
*
* Currently, we support hashjoin for binary opclauses where
* the operator is a hashjoinable operator. The arguments can be
* anything --- as long as there are no volatile functions in them.
*/
static void
check_hashjoinable(RestrictInfo *restrictinfo)
{
Expr *clause = restrictinfo->clause;
Oid opno;
Node *leftarg;
if (restrictinfo->pseudoconstant)
return;
if (!is_opclause(clause))
return;
if (list_length(((OpExpr *) clause)->args) != 2)
return;
opno = ((OpExpr *) clause)->opno;
leftarg = linitial(((OpExpr *) clause)->args);
if (op_hashjoinable(opno, exprType(leftarg)) &&
!contain_volatile_functions((Node *) clause))
restrictinfo->hashjoinoperator = opno;
}
View Git Blame Copy Permalink