database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-08-31 17:02:12 +03:00
Code Activity

RecentXmin is too recent to use as the cutoff point for accessing

Browse Source 
pg_subtrans --- what we need is the oldest xmin of any snapshot in use
in the current top transaction.  Introduce a new variable TransactionXmin
to play this role.  Fixes intermittent regression failure reported by
Neil Conway.
This commit is contained in:
Tom Lane
2004-09-16 18:35:23 +00:00
parent 8f9f198603
commit 86fff990b2
5 changed files with 41 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

34
src/backend/storage/ipc/sinval.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.73 2004/09/06 23:33:35 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.74 2004/09/16 18:35:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -521,7 +521,8 @@ TransactionIdIsInProgress(TransactionId xid)
bool locked;
/*
* Don't bother checking a very old transaction.
* Don't bother checking a transaction older than RecentXmin; it
* could not possibly still be running.
*/
if (TransactionIdPrecedes(xid, RecentXmin))
{
@@ -732,10 +733,19 @@ GetOldestXmin(bool allDbs)
* This ensures that the set of transactions seen as "running" by the
* current xact will not change after it takes the snapshot.
*
* We also compute the current global xmin (oldest xmin across all running
* transactions) and save it in RecentGlobalXmin. This is the same
* computation done by GetOldestXmin(TRUE). The xmin value is also stored
* into RecentXmin.
* Note that only top-level XIDs are included in the snapshot. We can
* still apply the xmin and xmax limits to subtransaction XIDs, but we
* need to work a bit harder to see if XIDs in [xmin..xmax) are running.
*
* We also update the following backend-global variables:
* TransactionXmin: the oldest xmin of any snapshot in use in the
* current transaction (this is the same as MyProc->xmin). This
* is just the xmin computed for the first, serializable snapshot.
* RecentXmin: the xmin computed for the most recent snapshot. XIDs
* older than this are known not running any more.
* RecentGlobalXmin: the global xmin (oldest TransactionXmin across all
* running transactions). This is the same computation done by
* GetOldestXmin(TRUE).
*----------
*/
Snapshot
@@ -751,6 +761,11 @@ GetSnapshotData(Snapshot snapshot, bool serializable)
Assert(snapshot != NULL);
/* Serializable snapshot must be computed before any other... */
Assert(serializable ?
!TransactionIdIsValid(MyProc->xmin) :
TransactionIdIsValid(MyProc->xmin));
/*
* Allocating space for MaxBackends xids is usually overkill;
* lastBackend would be sufficient. But it seems better to do the
@@ -850,13 +865,10 @@ GetSnapshotData(Snapshot snapshot, bool serializable)
}
if (serializable)
MyProc->xmin = xmin;
MyProc->xmin = TransactionXmin = xmin;
LWLockRelease(SInvalLock);
/* Serializable snapshot must be computed before any other... */
Assert(TransactionIdIsValid(MyProc->xmin));
/*
* Update globalxmin to include actual process xids. This is a
* slightly different way of computing it than GetOldestXmin uses, but
@@ -865,7 +877,7 @@ GetSnapshotData(Snapshot snapshot, bool serializable)
if (TransactionIdPrecedes(xmin, globalxmin))
globalxmin = xmin;
/* Update globals for use by VACUUM */
/* Update global variables too */
RecentGlobalXmin = globalxmin;
RecentXmin = xmin;