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Don't try to fetch database name when SetTransactionIdLimit() is executed

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outside a transaction.

This repairs brain fade in my patch of 2009-08-30: the reason we had been
storing oldest-database name, not OID, in ShmemVariableCache was of course
to avoid having to do a catalog lookup at times when it might be unsafe.

This error explains why Aleksandr Dushein is having trouble getting out of
an XID wraparound state in bug #5718, though not how he got into that state
in the first place.  I suspect pg_upgrade is at fault there.
This commit is contained in:
Tom Lane 2010-10-20 12:48:51 -04:00
parent 17a16663d0
commit def30e84c4
1 changed files with 14 additions and 4 deletions
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18
src/backend/access/transam/varsup.c
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@ -16,6 +16,7 @@
#include "access/clog.h"
#include "access/subtrans.h"
#include "access/transam.h"
#include "access/xact.h"
#include "commands/dbcommands.h"
#include "miscadmin.h"
#include "postmaster/autovacuum.h"
@ -346,13 +347,22 @@ SetTransactionIdLimit(TransactionId oldest_datfrozenxid, Oid oldest_datoid)
/* Give an immediate warning if past the wrap warn point */
if (TransactionIdFollowsOrEquals(curXid, xidWarnLimit) && !InRecovery)
{
char *oldest_datname = get_database_name(oldest_datoid);
char *oldest_datname;
/*
* Note: it's possible that get_database_name fails and returns NULL,
* for example because the database just got dropped. We'll still
* warn, even though the warning might now be unnecessary.
* We can be called when not inside a transaction, for example
* during StartupXLOG(). In such a case we cannot do database
* access, so we must just report the oldest DB's OID.
*
* Note: it's also possible that get_database_name fails and returns
* NULL, for example because the database just got dropped. We'll
* still warn, even though the warning might now be unnecessary.
*/
if (IsTransactionState())
oldest_datname = get_database_name(oldest_datoid);
else
oldest_datname = NULL;
if (oldest_datname)
ereport(WARNING,
(errmsg("database \"%s\" must be vacuumed within %u transactions",