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Fix another ancient memory-leak bug in relcache.c.

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CheckConstraintFetch() leaked a cstring in the caller's context for each
CHECK constraint expression it copied into the relcache.  Ordinarily that
isn't problematic, but it can be during CLOBBER_CACHE testing because so
many reloads can happen during a single query; so complicate the code
slightly to allow freeing the cstring after use.  Per testing on buildfarm
member barnacle.

This is exactly like the leak fixed in AttrDefaultFetch() by commit
078b2ed291.  (Yes, this time I did look for
other instances of the same coding pattern :-(.)  Like that patch, no
back-patch, since it seems unlikely that there's any problem except under
very artificial test conditions.

BTW, it strikes me that both of these places would require further work
comparable to commit ab8c84db2f, if we ever
supported defaults or check constraints on system catalogs: they both
assume they are copying into an empty relcache data structure, and that
conceivably wouldn't be the case during recursive reloading of a system
catalog.  This does not seem worth worrying about for the moment, since
there is no near-term prospect of supporting any such thing.  So I'll
just note the possibility for the archives' sake.
This commit is contained in:
Tom Lane
2014-08-24 11:56:52 -04:00
parent 256bfb2c9a
commit 73eba19aeb
1 changed files with 8 additions and 4 deletions
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12
src/backend/utils/cache/relcache.c vendored
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@@ -3552,8 +3552,6 @@ CheckConstraintFetch(Relation relation)
SysScanDesc conscan;
ScanKeyData skey[1];
HeapTuple htup;
Datum val;
bool isnull;
int found = 0;
ScanKeyInit(&skey[0],
@@ -3568,6 +3566,9 @@ CheckConstraintFetch(Relation relation)
while (HeapTupleIsValid(htup = systable_getnext(conscan)))
{
Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(htup);
Datum val;
bool isnull;
char *s;
/* We want check constraints only */
if (conform->contype != CONSTRAINT_CHECK)
@@ -3590,8 +3591,11 @@ CheckConstraintFetch(Relation relation)
elog(ERROR, "null conbin for rel %s",
RelationGetRelationName(relation));
check[found].ccbin = MemoryContextStrdup(CacheMemoryContext,
TextDatumGetCString(val));
/* detoast and convert to cstring in caller's context */
s = TextDatumGetCString(val);
check[found].ccbin = MemoryContextStrdup(CacheMemoryContext, s);
pfree(s);
found++;
}