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Nested transactions. There is still much left to do, especially on the

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performance front, but with feature freeze upon us I think it's time to
drive a stake in the ground and say that this will be in 7.5.

Alvaro Herrera, with some help from Tom Lane.
This commit is contained in:
Tom Lane
2004-07-01 00:52:04 +00:00
parent 4c9aa572fa
commit 573a71a5da
74 changed files with 4516 additions and 1144 deletions
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93
src/backend/storage/ipc/sinval.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.64 2004/06/02 21:29:28 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/ipc/sinval.c,v 1.65 2004/07/01 00:50:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -16,6 +16,8 @@
#include <signal.h>
#include "access/subtrans.h"
#include "access/transam.h"
#include "commands/async.h"
#include "storage/ipc.h"
#include "storage/proc.h"
@@ -428,20 +430,40 @@ DatabaseHasActiveBackends(Oid databaseId, bool ignoreMyself)
/*
* TransactionIdIsInProgress -- is given transaction running by some backend
*
* There are three possibilities for finding a running transaction:
*
* 1. the given Xid is a main transaction Id. We will find this out cheaply
* by looking at the PGPROC struct for each backend.
*
* 2. the given Xid is one of the cached subxact Xids in the PGPROC array.
* We can find this out cheaply too.
*
* 3. Search the SubTrans tree. This is the slowest, but sadly it has to be
* done always if the other two failed.
*
* SInvalLock has to be held while we do 1 and 2. If we save all the Xids
* while doing 1, we can release the SInvalLock while we do 3. This buys back
* some concurrency (we can't retrieve the main Xids from PGPROC again anyway,
* see GetNewTransactionId)
*/
bool
TransactionIdIsInProgress(TransactionId xid)
{
bool result = false;
SISeg *segP = shmInvalBuffer;
ProcState *stateP = segP->procState;
int index;
bool result = false;
SISeg *segP = shmInvalBuffer;
ProcState *stateP = segP->procState;
int i;
int nxids = 0;
TransactionId *xids;
xids = (TransactionId *)palloc(sizeof(TransactionId) * segP->maxBackends);
LWLockAcquire(SInvalLock, LW_SHARED);
for (index = 0; index < segP->lastBackend; index++)
for (i = 0; i < segP->lastBackend; i++)
{
SHMEM_OFFSET pOffset = stateP[index].procStruct;
SHMEM_OFFSET pOffset = stateP[i].procStruct;
if (pOffset != INVALID_OFFSET)
{
@@ -450,16 +472,71 @@ TransactionIdIsInProgress(TransactionId xid)
/* Fetch xid just once - see GetNewTransactionId */
TransactionId pxid = proc->xid;
/*
* check the main Xid (step 1 above)
*/
if (TransactionIdEquals(pxid, xid))
{
result = true;
break;
}
/*
* save the main Xid for step 3.
*/
xids[nxids++] = pxid;
#ifdef NOT_USED
FIXME -- waiting to save the Xids in PGPROC ...
/*
* check the saved Xids array (step 2)
*/
for (j = 0; j < PGPROC_MAX_SAVED_XIDS; j++)
{
pxid = proc->savedxids[j];
if (!TransactionIdIsValid(pxids))
break;
if (TransactionIdEquals(pxid, xid))
{
result = true;
break;
}
}
#endif
if (result)
break;
}
}
LWLockRelease(SInvalLock);
/*
* Step 3: have to check pg_subtrans. Use the saved Xids.
*
* XXX Could save the cached Xids too for further improvement.
*/
if (!result)
{
/* this is a potentially expensive call. */
xid = SubTransGetTopmostTransaction(xid);
Assert(TransactionIdIsValid(xid));
/*
* We don't care if it aborted, because if it did, we won't find
* it in the array.
*/
for (i = 0; i < nxids; i++)
if (TransactionIdEquals(xids[i], xid))
return true;
}
return result;
}
@@ -596,7 +673,7 @@ GetSnapshotData(Snapshot snapshot, bool serializable)
* This does open a possibility for avoiding repeated malloc/free:
* since MaxBackends does not change at runtime, we can simply reuse
* the previous xip array if any. (This relies on the fact that all
* calls pass static SnapshotData structs.)
* callers pass static SnapshotData structs.)
*/
if (snapshot->xip == NULL)
{