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Apply table and domain CHECK constraints in name order.

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Previously, CHECK constraints of the same scope were checked in whatever
order they happened to be read from pg_constraint.  (Usually, but not
reliably, this would be creation order for domain constraints and reverse
creation order for table constraints, because of differing implementation
details.)  Nondeterministic results of this sort are problematic at least
for testing purposes, and in discussion it was agreed to be a violation of
the principle of least astonishment.  Therefore, borrow the principle
already established for triggers, and apply such checks in name order
(using strcmp() sort rules).  This lets users control the check order
if they have a mind to.

Domain CHECK constraints still follow the rule of checking lower nested
domains' constraints first; the name sort only applies to multiple
constraints attached to the same domain.

In passing, I failed to resist the temptation to wordsmith a bit in
create_domain.sgml.

Apply to HEAD only, since this could result in a behavioral change in
existing applications, and the potential regression test failures have
not actually been observed in our buildfarm.
This commit is contained in:
Tom Lane
2015-03-23 16:59:29 -04:00
parent 871293fb7f
commit e5f455f59f
6 changed files with 129 additions and 24 deletions
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17
src/backend/utils/cache/relcache.c vendored
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@ -271,6 +271,7 @@ static TupleDesc GetPgClassDescriptor(void);
static TupleDesc GetPgIndexDescriptor(void);
static void AttrDefaultFetch(Relation relation);
static void CheckConstraintFetch(Relation relation);
static int CheckConstraintCmp(const void *a, const void *b);
static List *insert_ordered_oid(List *list, Oid datum);
static void IndexSupportInitialize(oidvector *indclass,
RegProcedure *indexSupport,
@ -3734,6 +3735,22 @@ CheckConstraintFetch(Relation relation)
if (found != ncheck)
elog(ERROR, "%d constraint record(s) missing for rel %s",
ncheck - found, RelationGetRelationName(relation));
/* Sort the records so that CHECKs are applied in a deterministic order */
if (ncheck > 1)
qsort(check, ncheck, sizeof(ConstrCheck), CheckConstraintCmp);
}
/*
* qsort comparator to sort ConstrCheck entries by name
*/
static int
CheckConstraintCmp(const void *a, const void *b)
{
const ConstrCheck *ca = (const ConstrCheck *) a;
const ConstrCheck *cb = (const ConstrCheck *) b;
return strcmp(ca->ccname, cb->ccname);
}
/*