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/*-------------------------------------------------------------------------
*
* joininfo.c
* joininfo list manipulation routines
*
* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/util/joininfo.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "optimizer/joininfo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
/*
* have_relevant_joinclause
* Detect whether there is a joinclause that involves
* the two given relations.
*
* Note: the joinclause does not have to be evaluable with only these two
* relations. This is intentional. For example consider
* SELECT * FROM a, b, c WHERE a.x = (b.y + c.z)
* If a is much larger than the other tables, it may be worthwhile to
* cross-join b and c and then use an inner indexscan on a.x. Therefore
* we should consider this joinclause as reason to join b to c, even though
* it can't be applied at that join step.
*/
bool
have_relevant_joinclause(PlannerInfo *root,
RelOptInfo *rel1, RelOptInfo *rel2)
{
bool result = false;
List *joininfo;
Relids other_relids;
ListCell *l;
/*
* We could scan either relation's joininfo list; may as well use the
* shorter one.
*/
if (list_length(rel1->joininfo) <= list_length(rel2->joininfo))
{
joininfo = rel1->joininfo;
other_relids = rel2->relids;
}
else
{
joininfo = rel2->joininfo;
other_relids = rel1->relids;
}
foreach(l, joininfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
if (bms_overlap(other_relids, rinfo->required_relids))
{
result = true;
break;
}
}
/*
* We also need to check the EquivalenceClass data structure, which might
* contain relationships not emitted into the joininfo lists.
*/
if (!result && rel1->has_eclass_joins && rel2->has_eclass_joins)
result = have_relevant_eclass_joinclause(root, rel1, rel2);
return result;
}
/*
* add_join_clause_to_rels
* Add 'restrictinfo' to the joininfo list of each relation it requires.
*
* Note that the same copy of the restrictinfo node is linked to by all the
* lists it is in. This allows us to exploit caching of information about
* the restriction clause (but we must be careful that the information does
* not depend on context).
*
* 'restrictinfo' describes the join clause
* 'join_relids' is the list of relations participating in the join clause
* (there must be more than one)
*/
void
add_join_clause_to_rels(PlannerInfo *root,
RestrictInfo *restrictinfo,
Relids join_relids)
{
int cur_relid;
cur_relid = -1;
while ((cur_relid = bms_next_member(join_relids, cur_relid)) >= 0)
{
RelOptInfo *rel = find_base_rel(root, cur_relid);
rel->joininfo = lappend(rel->joininfo, restrictinfo);
}
}
/*
* remove_join_clause_from_rels
* Delete 'restrictinfo' from all the joininfo lists it is in
*
* This reverses the effect of add_join_clause_to_rels. It's used when we
* discover that a relation need not be joined at all.
*
* 'restrictinfo' describes the join clause
* 'join_relids' is the list of relations participating in the join clause
* (there must be more than one)
*/
void
remove_join_clause_from_rels(PlannerInfo *root,
RestrictInfo *restrictinfo,
Relids join_relids)
{
int cur_relid;
cur_relid = -1;
while ((cur_relid = bms_next_member(join_relids, cur_relid)) >= 0)
{
RelOptInfo *rel = find_base_rel(root, cur_relid);
/*
* Remove the restrictinfo from the list. Pointer comparison is
* sufficient.
*/
Assert(list_member_ptr(rel->joininfo, restrictinfo));
rel->joininfo = list_delete_ptr(rel->joininfo, restrictinfo);
}
}
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