database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-30 11:03:19 +03:00
Code Activity

Solve the problem of OID collisions by probing for duplicate OIDs

Browse Source 
whenever we generate a new OID.  This prevents occasional duplicate-OID
errors that can otherwise occur once the OID counter has wrapped around.
Duplicate relfilenode values are also checked for when creating new
physical files.  Per my recent proposal.
This commit is contained in:
Tom Lane
2005-08-12 01:36:05 +00:00
parent 9e4a2de844
commit 721e53785d
20 changed files with 416 additions and 268 deletions
Download Patch File Download Diff File Expand all files Collapse all files

63
src/backend/access/transam/varsup.c
View File

@ -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);
}