diff options
Diffstat (limited to 'src/backend/access/transam/varsup.c')
| -rw-r--r-- | src/backend/access/transam/varsup.c | 63 |
1 files changed, 13 insertions, 50 deletions
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c index 5c51e69253e..9edb028a1cc 100644 --- a/src/backend/access/transam/varsup.c +++ b/src/backend/access/transam/varsup.c @@ -6,7 +6,7 @@ * Copyright (c) 2000-2005, PostgreSQL Global Development Group * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/access/transam/varsup.c,v 1.64 2005/05/19 21:35:45 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/varsup.c,v 1.65 2005/08/12 01:35:55 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -247,13 +247,16 @@ SetTransactionIdLimit(TransactionId oldest_datfrozenxid, } -/* ---------------------------------------------------------------- - * object id generation support - * ---------------------------------------------------------------- +/* + * GetNewObjectId -- allocate a new OID + * + * OIDs are generated by a cluster-wide counter. Since they are only 32 bits + * wide, counter wraparound will occur eventually, and therefore it is unwise + * to assume they are unique unless precautions are taken to make them so. + * Hence, this routine should generally not be used directly. The only + * direct callers should be GetNewOid() and GetNewRelFileNode() in + * catalog/catalog.c. */ - -static Oid lastSeenOid = InvalidOid; - Oid GetNewObjectId(void) { @@ -265,8 +268,9 @@ GetNewObjectId(void) * Check for wraparound of the OID counter. We *must* not return 0 * (InvalidOid); and as long as we have to check that, it seems a good * idea to skip over everything below FirstNormalObjectId too. (This - * basically just reduces the odds of OID collision right after a wrap - * occurs.) Note we are relying on unsigned comparison here. + * basically just avoids lots of collisions with bootstrap-assigned OIDs + * right after a wrap occurs, so as to avoid a possibly large number of + * iterations in GetNewOid.) Note we are relying on unsigned comparison. * * During initdb, we start the OID generator at FirstBootstrapObjectId, * so we only enforce wrapping to that point when in bootstrap or @@ -310,46 +314,5 @@ GetNewObjectId(void) LWLockRelease(OidGenLock); - lastSeenOid = result; - return result; } - -void -CheckMaxObjectId(Oid assigned_oid) -{ - if (lastSeenOid != InvalidOid && assigned_oid < lastSeenOid) - return; - - LWLockAcquire(OidGenLock, LW_EXCLUSIVE); - - if (assigned_oid < ShmemVariableCache->nextOid) - { - lastSeenOid = ShmemVariableCache->nextOid - 1; - LWLockRelease(OidGenLock); - return; - } - - /* If we are in the logged oid range, just bump nextOid up */ - if (assigned_oid <= ShmemVariableCache->nextOid + - ShmemVariableCache->oidCount - 1) - { - ShmemVariableCache->oidCount -= - assigned_oid - ShmemVariableCache->nextOid + 1; - ShmemVariableCache->nextOid = assigned_oid + 1; - LWLockRelease(OidGenLock); - return; - } - - /* - * We have exceeded the logged oid range. We should lock the database - * and kill all other backends but we are loading oid's that we can - * not guarantee are unique anyway, so we must rely on the user. - */ - - XLogPutNextOid(assigned_oid + VAR_OID_PREFETCH); - ShmemVariableCache->nextOid = assigned_oid + 1; - ShmemVariableCache->oidCount = VAR_OID_PREFETCH - 1; - - LWLockRelease(OidGenLock); -} |