diff options
Diffstat (limited to 'src/backend/commands')
| -rw-r--r-- | src/backend/commands/indexcmds.c | 38 |
1 files changed, 36 insertions, 2 deletions
diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c index c3ec2076a52..f2898fee5fc 100644 --- a/src/backend/commands/indexcmds.c +++ b/src/backend/commands/indexcmds.c @@ -2592,7 +2592,9 @@ makeObjectName(const char *name1, const char *name2, const char *label) * constraint names.) * * Note: it is theoretically possible to get a collision anyway, if someone - * else chooses the same name concurrently. This is fairly unlikely to be + * else chooses the same name concurrently. We shorten the race condition + * window by checking for conflicting relations using SnapshotDirty, but + * that doesn't close the window entirely. This is fairly unlikely to be * a problem in practice, especially if one is holding an exclusive lock on * the relation identified by name1. However, if choosing multiple names * within a single command, you'd better create the new object and do @@ -2608,15 +2610,45 @@ ChooseRelationName(const char *name1, const char *name2, int pass = 0; char *relname = NULL; char modlabel[NAMEDATALEN]; + SnapshotData SnapshotDirty; + Relation pgclassrel; + + /* prepare to search pg_class with a dirty snapshot */ + InitDirtySnapshot(SnapshotDirty); + pgclassrel = table_open(RelationRelationId, AccessShareLock); /* try the unmodified label first */ strlcpy(modlabel, label, sizeof(modlabel)); for (;;) { + ScanKeyData key[2]; + SysScanDesc scan; + bool collides; + relname = makeObjectName(name1, name2, modlabel); - if (!OidIsValid(get_relname_relid(relname, namespaceid))) + /* is there any conflicting relation name? */ + ScanKeyInit(&key[0], + Anum_pg_class_relname, + BTEqualStrategyNumber, F_NAMEEQ, + CStringGetDatum(relname)); + ScanKeyInit(&key[1], + Anum_pg_class_relnamespace, + BTEqualStrategyNumber, F_OIDEQ, + ObjectIdGetDatum(namespaceid)); + + scan = systable_beginscan(pgclassrel, ClassNameNspIndexId, + true /* indexOK */ , + &SnapshotDirty, + 2, key); + + collides = HeapTupleIsValid(systable_getnext(scan)); + + systable_endscan(scan); + + /* break out of loop if no conflict */ + if (!collides) { if (!isconstraint || !ConstraintNameExists(relname, namespaceid)) @@ -2628,6 +2660,8 @@ ChooseRelationName(const char *name1, const char *name2, snprintf(modlabel, sizeof(modlabel), "%s%d", label, ++pass); } + table_close(pgclassrel, AccessShareLock); + return relname; } |