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Fix CREATE INDEX CONCURRENTLY for the newest prepared transactions.

Browse Source 
The purpose of commit 8a54e12a38 was to
fix this, and it sufficed when the PREPARE TRANSACTION completed before
the CIC looked for lock conflicts.  Otherwise, things still broke.  As
before, in a cluster having used CIC while having enabled prepared
transactions, queries that use the resulting index can silently fail to
find rows.  It may be necessary to reindex to recover from past
occurrences; REINDEX CONCURRENTLY suffices.  Fix this for future index
builds by making CIC wait for arbitrarily-recent prepared transactions
and for ordinary transactions that may yet PREPARE TRANSACTION.  As part
of that, have PREPARE TRANSACTION transfer locks to its dummy PGPROC
before it calls ProcArrayClearTransaction().  Back-patch to 9.6 (all
supported versions).

Andrey Borodin, reviewed (in earlier versions) by Andres Freund.

Discussion: https://postgr.es/m/01824242-AA92-4FE9-9BA7-AEBAFFEA3D0C@yandex-team.ru
This commit is contained in:
Noah Misch
2021-10-23 18:36:38 -07:00
parent fdd965d074
commit 3cd9c3b921
8 changed files with 362 additions and 36 deletions
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63
src/backend/access/transam/twophase.c
View File

@@ -459,14 +459,24 @@ MarkAsPreparingGuts(GlobalTransaction gxact, TransactionId xid, const char *gid,
proc->pgprocno = gxact->pgprocno;
SHMQueueElemInit(&(proc->links));
proc->waitStatus = PROC_WAIT_STATUS_OK;
/* We set up the gxact's VXID as InvalidBackendId/XID */
proc->lxid = (LocalTransactionId) xid;
if (LocalTransactionIdIsValid(MyProc->lxid))
{
/* clone VXID, for TwoPhaseGetXidByVirtualXID() to find */
proc->lxid = MyProc->lxid;
proc->backendId = MyBackendId;
}
else
{
Assert(AmStartupProcess() || !IsPostmasterEnvironment);
/* GetLockConflicts() uses this to specify a wait on the XID */
proc->lxid = xid;
proc->backendId = InvalidBackendId;
}
proc->xid = xid;
Assert(proc->xmin == InvalidTransactionId);
proc->delayChkpt = false;
proc->statusFlags = 0;
proc->pid = 0;
proc->backendId = InvalidBackendId;
proc->databaseId = databaseid;
proc->roleId = owner;
proc->tempNamespaceId = InvalidOid;
@@ -846,6 +856,53 @@ TwoPhaseGetGXact(TransactionId xid, bool lock_held)
return result;
}
/*
* TwoPhaseGetXidByVirtualXID
* Lookup VXID among xacts prepared since last startup.
*
* (This won't find recovered xacts.) If more than one matches, return any
* and set "have_more" to true. To witness multiple matches, a single
* BackendId must consume 2^32 LXIDs, with no intervening database restart.
*/
TransactionId
TwoPhaseGetXidByVirtualXID(VirtualTransactionId vxid,
bool *have_more)
{
int i;
TransactionId result = InvalidTransactionId;
Assert(VirtualTransactionIdIsValid(vxid));
LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
{
GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
PGPROC *proc;
VirtualTransactionId proc_vxid;
if (!gxact->valid)
continue;
proc = &ProcGlobal->allProcs[gxact->pgprocno];
GET_VXID_FROM_PGPROC(proc_vxid, *proc);
if (VirtualTransactionIdEquals(vxid, proc_vxid))
{
/* Startup process sets proc->backendId to InvalidBackendId. */
Assert(!gxact->inredo);
if (result != InvalidTransactionId)
{
*have_more = true;
break;
}
result = gxact->xid;
}
}
LWLockRelease(TwoPhaseStateLock);
return result;
}
/*
* TwoPhaseGetDummyBackendId
* Get the dummy backend ID for prepared transaction specified by XID