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Add code to prevent transaction ID wraparound by enforcing a safe limit

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in GetNewTransactionId().  Since the limit value has to be computed
before we run any real transactions, this requires adding code to database
startup to scan pg_database and determine the oldest datfrozenxid.
This can conveniently be combined with the first stage of an attack on
the problem that the 'flat file' copies of pg_shadow and pg_group are
not properly updated during WAL recovery.  The code I've added to
startup resides in a new file src/backend/utils/init/flatfiles.c, and
it is responsible for rewriting the flat files as well as initializing
the XID wraparound limit value.  This will eventually allow us to get
rid of GetRawDatabaseInfo too, but we'll need an initdb so we can add
a trigger to pg_database.
This commit is contained in:
Tom Lane
2005-02-20 02:22:07 +00:00
parent 617d16f4ff
commit 60b2444cc3
15 changed files with 1191 additions and 571 deletions
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48
src/backend/access/transam/xact.c
View File

@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.195 2004/12/31 21:59:29 pgsql Exp $
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.196 2005/02/20 02:21:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -28,7 +28,6 @@
#include "commands/async.h"
#include "commands/tablecmds.h"
#include "commands/trigger.h"
#include "commands/user.h"
#include "executor/spi.h"
#include "libpq/be-fsstubs.h"
#include "miscadmin.h"
@ -36,6 +35,7 @@
#include "storage/proc.h"
#include "storage/sinval.h"
#include "storage/smgr.h"
#include "utils/flatfiles.h"
#include "utils/guc.h"
#include "utils/inval.h"
#include "utils/memutils.h"
@ -1354,6 +1354,7 @@ StartTransaction(void)
* start processing
*/
s->state = TRANS_START;
s->transactionId = InvalidTransactionId; /* until assigned */
/*
* Make sure we've freed any old snapshot, and reset xact state
@ -1464,9 +1465,9 @@ CommitTransaction(void)
/* NOTIFY commit must come before lower-level cleanup */
AtCommit_Notify();
/* Update the flat password file if we changed pg_shadow or pg_group */
/* Update flat files if we changed pg_database, pg_shadow or pg_group */
/* This should be the last step before commit */
AtEOXact_UpdatePasswordFile(true);
AtEOXact_UpdateFlatFiles(true);
/* Prevent cancel/die interrupt while cleaning up */
HOLD_INTERRUPTS();
@ -1654,10 +1655,14 @@ AbortTransaction(void)
AtAbort_Portals();
AtEOXact_LargeObject(false); /* 'false' means it's abort */
AtAbort_Notify();
AtEOXact_UpdatePasswordFile(false);
AtEOXact_UpdateFlatFiles(false);
/* Advertise the fact that we aborted in pg_clog. */
RecordTransactionAbort();
/*
* Advertise the fact that we aborted in pg_clog (assuming that we
* got as far as assigning an XID to advertise).
*/
if (TransactionIdIsValid(s->transactionId))
RecordTransactionAbort();
/*
* Let others know about no transaction in progress by me. Note that
@ -2034,10 +2039,25 @@ AbortCurrentTransaction(void)
switch (s->blockState)
{
/*
* we aren't in a transaction, so we do nothing.
*/
case TBLOCK_DEFAULT:
if (s->state == TRANS_DEFAULT)
{
/* we are idle, so nothing to do */
}
else
{
/*
* We can get here after an error during transaction start
* (state will be TRANS_START). Need to clean up the
* incompletely started transaction. First, adjust the
* low-level state to suppress warning message from
* AbortTransaction.
*/
if (s->state == TRANS_START)
s->state = TRANS_INPROGRESS;
AbortTransaction();
CleanupTransaction();
}
break;
/*
@ -3277,8 +3297,8 @@ CommitSubTransaction(void)
AtEOSubXact_LargeObject(true, s->subTransactionId,
s->parent->subTransactionId);
AtSubCommit_Notify();
AtEOSubXact_UpdatePasswordFile(true, s->subTransactionId,
s->parent->subTransactionId);
AtEOSubXact_UpdateFlatFiles(true, s->subTransactionId,
s->parent->subTransactionId);
CallSubXactCallbacks(SUBXACT_EVENT_COMMIT_SUB, s->subTransactionId,
s->parent->subTransactionId);
@ -3387,8 +3407,8 @@ AbortSubTransaction(void)
AtEOSubXact_LargeObject(false, s->subTransactionId,
s->parent->subTransactionId);
AtSubAbort_Notify();
AtEOSubXact_UpdatePasswordFile(false, s->subTransactionId,
s->parent->subTransactionId);
AtEOSubXact_UpdateFlatFiles(false, s->subTransactionId,
s->parent->subTransactionId);
/* Advertise the fact that we aborted in pg_clog. */
if (TransactionIdIsValid(s->transactionId))