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Load FK defs into relcache for use by planner

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Fastpath ignores this if no triggers defined.

Author: Tomas Vondra, with fastpath and comments added by me
Reviewers: David Rowley, Simon Riggs
This commit is contained in:
Simon Riggs
2016-04-07 12:08:33 +01:00
parent f2b1b3079c
commit 015e88942a
7 changed files with 199 additions and 1 deletions
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75
src/backend/utils/cache/relcache.c vendored
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@ -2031,6 +2031,7 @@ RelationDestroyRelation(Relation relation, bool remember_tupdesc)
FreeTupleDesc(relation->rd_att);
}
list_free(relation->rd_indexlist);
list_free(relation->rd_fkeylist);
bms_free(relation->rd_indexattr);
bms_free(relation->rd_keyattr);
bms_free(relation->rd_idattr);
@ -3956,6 +3957,79 @@ RelationGetIndexList(Relation relation)
return result;
}
/*
* RelationGetFKeyList -- get a list of foreign key oids
*
* Use an index scan on pg_constraint to load in FK definitions,
* intended for use within the planner, not for enforcing FKs.
*
* Data is ordered by Oid, though this is not critical at this point
* since we do not lock the referenced relations.
*/
List *
RelationGetFKeyList(Relation relation)
{
Relation conrel;
SysScanDesc conscan;
ScanKeyData skey;
HeapTuple htup;
List *result;
List *oldlist;
MemoryContext oldcxt;
/* Quick exit if we already computed the list. */
if (relation->rd_fkeylist)
return list_copy(relation->rd_fkeylist);
/* Fast path if no FKs... if it doesn't have a trigger, it can't have a FK */
if (!relation->rd_rel->relhastriggers)
return NIL;
/*
* We build the list we intend to return (in the caller's context) while
* doing the scan. After successfully completing the scan, we copy that
* list into the relcache entry. This avoids cache-context memory leakage
* if we get some sort of error partway through.
*/
result = NIL;
/* Prepare to scan pg_constraint for entries having conrelid = this rel. */
ScanKeyInit(&skey,
Anum_pg_constraint_conrelid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(RelationGetRelid(relation)));
conrel = heap_open(ConstraintRelationId, AccessShareLock);
conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
NULL, 1, &skey);
while (HeapTupleIsValid(htup = systable_getnext(conscan)))
{
Form_pg_constraint constraint = (Form_pg_constraint) GETSTRUCT(htup);
/* return only foreign keys */
if (constraint->contype != CONSTRAINT_FOREIGN)
continue;
/* Add FK's OID to result list in the proper order */
result = insert_ordered_oid(result, HeapTupleGetOid(htup));
}
systable_endscan(conscan);
heap_close(conrel, AccessShareLock);
/* Now save a copy of the completed list in the relcache entry. */
oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
oldlist = relation->rd_fkeylist;
relation->rd_fkeylist = list_copy(result);
MemoryContextSwitchTo(oldcxt);
/* Don't leak the old list, if there is one */
list_free(oldlist);
return result;
}
/*
* insert_ordered_oid
* Insert a new Oid into a sorted list of Oids, preserving ordering
@ -4920,6 +4994,7 @@ load_relcache_init_file(bool shared)
rel->rd_indexattr = NULL;
rel->rd_keyattr = NULL;
rel->rd_idattr = NULL;
rel->rd_fkeylist = NIL;
rel->rd_createSubid = InvalidSubTransactionId;
rel->rd_newRelfilenodeSubid = InvalidSubTransactionId;
rel->rd_amcache = NULL;