Simon Riggs wrote:
> OK, spent long time testing various batching scenarios for this using a
> custom test harness to simulate various spreads of xids in transaction
> trees. All looks fine now.
I had a look and was mostly rephrasing some comments and the README
(hopefully I didn't make any of them worse than they were), when I
noticed that the code to iterate thru pages could be refactored. I
think the change makes the algorithm in TransactionIdSetTreeStatus
easier to follow.
I also noticed that TransactionIdSetPageStatus has a "subcommit" arg
which is unexplained. I sort-of understand the point, but I think it's
better that you fill in the explanation in the header comment (marked
with XXX)
I hope I didn't break the code with the new function
set_tree_status_by_pages -- please recheck that part.
I didn't test this beyond regression tests.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
Index: src/backend/access/transam/README
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/access/transam/README,v
retrieving revision 1.11
diff -c -p -r1.11 README
*** src/backend/access/transam/README 21 Mar 2008 13:23:28 -0000 1.11
--- src/backend/access/transam/README 5 Oct 2008 18:33:40 -0000
*************** from disk. They also allow information
*** 341,351 ****
pg_clog records the commit status for each transaction that has been assigned
an XID. A transaction can be in progress, committed, aborted, or
"sub-committed". This last state means that it's a subtransaction that's no
! longer running, but its parent has not updated its state yet (either it is
! still running, or the backend crashed without updating its status). A
! sub-committed transaction's status will be updated again to the final value as
! soon as the parent commits or aborts, or when the parent is detected to be
! aborted.
Savepoints are implemented using subtransactions. A subtransaction is a
transaction inside a transaction; its commit or abort status is not only
--- 341,360 ----
pg_clog records the commit status for each transaction that has been assigned
an XID. A transaction can be in progress, committed, aborted, or
"sub-committed". This last state means that it's a subtransaction that's no
! longer running, but its parent has not updated its state yet. It is not
! necessary to update a subtransaction's transaction status to subcommit, so we
! can just defer it until main transaction commit. The main role of marking
! transactions as sub-committed is to provide an atomic commit protocol when
! transaction status is spread across multiple clog pages. As a result, whenever
! transaction status spreads across multiple pages we must use a two-phase commit
! protocol: the first phase is to mark the subtransactions as sub-committed, then
! we mark the top level transaction and all its subtransactions committed (in
! that order). Thus, subtransactions that have not aborted appear as in-progress
! even when they have already finished, and the subcommit status appears as a
! very short transitoty state during main transaction commit. Subtransaction
! abort is always marked in clog as soon as it occurs. When the transaction
! status all fit in a single CLOG page, we atomically mark them all as committed
! without bothering with the intermediate sub-commit state.
Savepoints are implemented using subtransactions. A subtransaction is a
transaction inside a transaction; its commit or abort status is not only
Index: src/backend/access/transam/clog.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/access/transam/clog.c,v
retrieving revision 1.47
diff -c -p -r1.47 clog.c
*** src/backend/access/transam/clog.c 1 Aug 2008 13:16:08 -0000 1.47
--- src/backend/access/transam/clog.c 5 Oct 2008 18:36:12 -0000
*************** static int ZeroCLOGPage(int pageno, bool
*** 80,107 ****
static bool CLOGPagePrecedes(int page1, int page2);
static void WriteZeroPageXlogRec(int pageno);
static void WriteTruncateXlogRec(int pageno);
/*
! * Record the final state of a transaction in the commit log.
*
* lsn must be the WAL location of the commit record when recording an async
* commit. For a synchronous commit it can be InvalidXLogRecPtr, since the
* caller guarantees the commit record is already flushed in that case. It
* should be InvalidXLogRecPtr for abort cases, too.
*
* NB: this is a low-level routine and is NOT the preferred entry point
! * for most uses; TransactionLogUpdate() in transam.c is the intended caller.
*/
void
! TransactionIdSetStatus(TransactionId xid, XidStatus status, XLogRecPtr lsn)
{
- int pageno = TransactionIdToPage(xid);
- int byteno = TransactionIdToByte(xid);
- int bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
int slotno;
! char *byteptr;
! char byteval;
Assert(status == TRANSACTION_STATUS_COMMITTED ||
status == TRANSACTION_STATUS_ABORTED ||
--- 80,249 ----
static bool CLOGPagePrecedes(int page1, int page2);
static void WriteZeroPageXlogRec(int pageno);
static void WriteTruncateXlogRec(int pageno);
+ static void TransactionIdSetPageStatus(TransactionId xid, int nsubxids,
+ TransactionId *subxids, XidStatus status,
+ XLogRecPtr lsn, int pageno, bool subcommit);
+ static void TransactionIdSetStatusBit(TransactionId xid, XidStatus status,
+ XLogRecPtr lsn, int slotno);
+ static void set_tree_status_by_pages(int nsubxids, TransactionId *subxids,
+ XidStatus status, XLogRecPtr lsn, bool subcommit);
/*
! * TransactionIdSetTreeStatus
! *
! * Record the final state of transaction entries in the commit log for
! * a transaction and its subtransaction tree. Take care to ensure this is
! * efficient, and as atomic as possible.
! *
! * xid is a single xid to set status for. This will typically be
! * the top level transactionid for a top level commit or abort. It can
! * also be a subtransaction when we record transaction aborts.
! *
! * subxids is an array of xids of length nsubxids, representing subtransactions
! * in the tree of xid. In various cases nsubxids may be zero.
*
* lsn must be the WAL location of the commit record when recording an async
* commit. For a synchronous commit it can be InvalidXLogRecPtr, since the
* caller guarantees the commit record is already flushed in that case. It
* should be InvalidXLogRecPtr for abort cases, too.
*
+ * In the commit case, atomicity is limited by whether all the subxids are in
+ * the same CLOG page as xid. If they all are, then the lock will be grabbed
+ * only once, and the status will be set to committed directly. Otherwise
+ * we must
+ * 1. set sub-committed all subxids that are not on the same page as the
+ * main xid
+ * 2. atomically set committed the main xid and the subxids on the same page
+ * 3. go over the first bunch again and set them committed
+ * Note that as far as concurrent checkers are concerned, main transaction
+ * commit as a whole is still atomic.
+ *
* NB: this is a low-level routine and is NOT the preferred entry point
! * for most uses; functions in transam.c are the intended callers.
! *
! * XXX Think about issuing FADVISE_WILLNEED on pages that we will need,
! * but aren't yet in cache, as well as hinting pages not to fall out of
! * cache yet.
*/
void
! TransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
! TransactionId *subxids, XidStatus status, XLogRecPtr lsn)
! {
! int pageno = TransactionIdToPage(xid); /* get page of parent */
! int i;
!
! Assert(status == TRANSACTION_STATUS_COMMITTED ||
! status == TRANSACTION_STATUS_ABORTED);
!
! /*
! * See how many subxids, if any, are on the same page as the parent, if any.
! */
! for (i = 0; i < nsubxids; i++)
! {
! if (TransactionIdToPage(subxids[i]) != pageno)
! break;
! }
!
! /*
! * Do all items fit on a single page?
! */
! if (i == nsubxids)
! {
! /*
! * Set the parent and all subtransactions in a single call
! */
! TransactionIdSetPageStatus(xid, nsubxids, subxids, status, lsn,
! pageno, true);
! }
! else
! {
! int num_on_first_page = i;
!
! /*
! * If this is a commit then we care about doing this correctly (i.e.
! * using the subcommitted intermediate status). By here, we know we're
! * updating more than one page of clog, so we must mark entries that
! * are *not* on the first page so that they show as subcommitted before
! * we then return to update the status to fully committed.
! *
! * To avoid touching the first page twice, skip marking subcommitted
! * those subxids in that first page.
! */
! if (status == TRANSACTION_STATUS_COMMITTED)
! set_tree_status_by_pages(nsubxids - num_on_first_page,
! subxids + num_on_first_page,
! TRANSACTION_STATUS_SUB_COMMITTED, lsn, true);
!
! /*
! * Now set the parent and subtransactions on same page as the parent,
! * if any
! */
! pageno = TransactionIdToPage(xid);
! TransactionIdSetPageStatus(xid, num_on_first_page, subxids, status,
! lsn, pageno, true);
!
! /*
! * By now, all subtransactions have been subcommitted, so all calls
! * to TransactionIdSetPageStatus() will use subcommit=false after
! * this point for this transaction tree.
! */
!
! /*
! * Now work through the rest of the subxids one clog page at a time,
! * starting from the second page onwards, like we did above.
! */
! set_tree_status_by_pages(nsubxids - num_on_first_page,
! subxids + num_on_first_page,
! status, lsn, false);
! }
! }
!
! /*
! * Helper for TransactionIdSetTreeStatus: set the status for a bunch of
! * transactions, chunking in the separate CLOG pages involved.
! */
! static void
! set_tree_status_by_pages(int nsubxids, TransactionId *subxids,
! XidStatus status, XLogRecPtr lsn, bool subcommit)
! {
! int pageno = TransactionIdToPage(subxids[0]);
! int offset = 0;
! int i = 0;
!
! while (i < nsubxids)
! {
! int num_on_page = 0;
!
! while (TransactionIdToPage(subxids[i]) == pageno && i < nsubxids)
! {
! num_on_page++;
! i++;
! }
!
! TransactionIdSetPageStatus(InvalidTransactionId,
! num_on_page, subxids + offset,
! status, lsn, pageno, subcommit);
! offset = i;
! pageno = TransactionIdToPage(subxids[offset]);
! }
! }
!
! /*
! * Record the final state of transaction entries in the commit log for
! * all entries on a single page. Atomic only on this page.
! *
! * Otherwise API is same as TransactionIdSetTreeStatus()
! *
! * XXX describe what "subcommit" is for.
! */
! static void
! TransactionIdSetPageStatus(TransactionId xid, int nsubxids,
! TransactionId *subxids, XidStatus status,
! XLogRecPtr lsn, int pageno, bool subcommit)
{
int slotno;
! int i;
Assert(status == TRANSACTION_STATUS_COMMITTED ||
status == TRANSACTION_STATUS_ABORTED ||
*************** TransactionIdSetStatus(TransactionId xid
*** 116,124 ****
* mustn't let it reach disk until we've done the appropriate WAL flush.
* But when lsn is invalid, it's OK to scribble on a page while it is
* write-busy, since we don't care if the update reaches disk sooner than
! * we think. Hence, pass write_ok = XLogRecPtrIsInvalid(lsn).
*/
slotno = SimpleLruReadPage(ClogCtl, pageno, XLogRecPtrIsInvalid(lsn), xid);
byteptr = ClogCtl->shared->page_buffer[slotno] + byteno;
/* Current state should be 0, subcommitted or target state */
--- 258,317 ----
* mustn't let it reach disk until we've done the appropriate WAL flush.
* But when lsn is invalid, it's OK to scribble on a page while it is
* write-busy, since we don't care if the update reaches disk sooner than
! * we think.
*/
slotno = SimpleLruReadPage(ClogCtl, pageno, XLogRecPtrIsInvalid(lsn), xid);
+
+ /*
+ * If we sync-commit more than one xid on this page while it is being
+ * written out, we might find that some of the bits go to disk and others
+ * don't. That would break atomicity, so if we haven't already
+ * subcommitted the xids for this commit, we do that first and then come
+ * back to start marking commits.
+ *
+ * If using async commit then we already waited for the write I/O to
+ * complete by this point, so nothing to do.
+ */
+ if (subcommit && status == TRANSACTION_STATUS_COMMITTED &&
+ XLogRecPtrIsInvalid(lsn))
+ {
+ for (i = 0; i < nsubxids; i++)
+ {
+ Assert(ClogCtl->shared->page_number[slotno] == TransactionIdToPage(subxids[i]));
+ TransactionIdSetStatusBit(subxids[i],
+ TRANSACTION_STATUS_SUB_COMMITTED, lsn, slotno);
+ }
+ }
+
+ /* Set the main transaction id, if any */
+ if (TransactionIdIsValid(xid))
+ TransactionIdSetStatusBit(xid, status, lsn, slotno);
+
+ /* Set the subtransactions */
+ for (i = 0; i < nsubxids; i++)
+ {
+ Assert(ClogCtl->shared->page_number[slotno] == TransactionIdToPage(subxids[i]));
+ TransactionIdSetStatusBit(subxids[i], status, lsn, slotno);
+ }
+
+ ClogCtl->shared->page_dirty[slotno] = true;
+
+ LWLockRelease(CLogControlLock);
+ }
+
+ /*
+ * Sets the commit status of a single transaction.
+ *
+ * Must be called with CLogControlLock held
+ */
+ static void
+ TransactionIdSetStatusBit(TransactionId xid, XidStatus status, XLogRecPtr lsn, int slotno)
+ {
+ int byteno = TransactionIdToByte(xid);
+ int bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
+ char *byteptr;
+ char byteval;
+
byteptr = ClogCtl->shared->page_buffer[slotno] + byteno;
/* Current state should be 0, subcommitted or target state */
*************** TransactionIdSetStatus(TransactionId xid
*** 132,139 ****
byteval |= (status << bshift);
*byteptr = byteval;
- ClogCtl->shared->page_dirty[slotno] = true;
-
/*
* Update the group LSN if the transaction completion LSN is higher.
*
--- 325,330 ----
*************** TransactionIdSetStatus(TransactionId xid
*** 150,156 ****
ClogCtl->shared->group_lsn[lsnindex] = lsn;
}
- LWLockRelease(CLogControlLock);
}
/*
--- 341,346 ----
Index: src/backend/access/transam/transam.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/access/transam/transam.c,v
retrieving revision 1.76
diff -c -p -r1.76 transam.c
*** src/backend/access/transam/transam.c 26 Mar 2008 18:48:59 -0000 1.76
--- src/backend/access/transam/transam.c 5 Oct 2008 18:46:01 -0000
*************** static const XLogRecPtr InvalidXLogRecPt
*** 40,54 ****
/* Local functions */
static XidStatus TransactionLogFetch(TransactionId transactionId);
- static void TransactionLogUpdate(TransactionId transactionId,
- XidStatus status, XLogRecPtr lsn);
/* ----------------------------------------------------------------
* Postgres log access method interface
*
* TransactionLogFetch
- * TransactionLogUpdate
* ----------------------------------------------------------------
*/
--- 40,51 ----
*************** TransactionLogFetch(TransactionId transa
*** 100,140 ****
return xidstatus;
}
- /*
- * TransactionLogUpdate
- *
- * Store the new status of a transaction. The commit record LSN must be
- * passed when recording an async commit; else it should be InvalidXLogRecPtr.
- */
- static inline void
- TransactionLogUpdate(TransactionId transactionId,
- XidStatus status, XLogRecPtr lsn)
- {
- /*
- * update the commit log
- */
- TransactionIdSetStatus(transactionId, status, lsn);
- }
-
- /*
- * TransactionLogMultiUpdate
- *
- * Update multiple transaction identifiers to a given status.
- * Don't depend on this being atomic; it's not.
- */
- static inline void
- TransactionLogMultiUpdate(int nxids, TransactionId *xids,
- XidStatus status, XLogRecPtr lsn)
- {
- int i;
-
- Assert(nxids != 0);
-
- for (i = 0; i < nxids; i++)
- TransactionIdSetStatus(xids[i], status, lsn);
- }
-
-
/* ----------------------------------------------------------------
* Interface functions
*
--- 97,102 ----
*************** TransactionLogMultiUpdate(int nxids, Tra
*** 144,154 ****
* these functions test the transaction status of
* a specified transaction id.
*
! * TransactionIdCommit
! * TransactionIdAbort
* ========
! * these functions set the transaction status
! * of the specified xid.
*
* See also TransactionIdIsInProgress, which once was in this module
* but now lives in procarray.c.
--- 106,117 ----
* these functions test the transaction status of
* a specified transaction id.
*
! * TransactionIdCommitTree
! * TransactionIdAsyncCommitTree
! * TransactionIdAbortTree
* ========
! * these functions set the transaction status of the specified
! * transaction tree.
*
* See also TransactionIdIsInProgress, which once was in this module
* but now lives in procarray.c.
*************** TransactionIdIsKnownCompleted(Transactio
*** 287,362 ****
return false;
}
-
- /*
- * TransactionIdCommit
- * Commits the transaction associated with the identifier.
- *
- * Note:
- * Assumes transaction identifier is valid.
- */
- void
- TransactionIdCommit(TransactionId transactionId)
- {
- TransactionLogUpdate(transactionId, TRANSACTION_STATUS_COMMITTED,
- InvalidXLogRecPtr);
- }
-
- /*
- * TransactionIdAsyncCommit
- * Same as above, but for async commits. The commit record LSN is needed.
- */
- void
- TransactionIdAsyncCommit(TransactionId transactionId, XLogRecPtr lsn)
- {
- TransactionLogUpdate(transactionId, TRANSACTION_STATUS_COMMITTED, lsn);
- }
-
- /*
- * TransactionIdAbort
- * Aborts the transaction associated with the identifier.
- *
- * Note:
- * Assumes transaction identifier is valid.
- * No async version of this is needed.
- */
- void
- TransactionIdAbort(TransactionId transactionId)
- {
- TransactionLogUpdate(transactionId, TRANSACTION_STATUS_ABORTED,
- InvalidXLogRecPtr);
- }
-
- /*
- * TransactionIdSubCommit
- * Marks the subtransaction associated with the identifier as
- * sub-committed.
- *
- * Note:
- * No async version of this is needed.
- */
- void
- TransactionIdSubCommit(TransactionId transactionId)
- {
- TransactionLogUpdate(transactionId, TRANSACTION_STATUS_SUB_COMMITTED,
- InvalidXLogRecPtr);
- }
-
/*
* TransactionIdCommitTree
! * Marks all the given transaction ids as committed.
*
! * The caller has to be sure that this is used only to mark subcommitted
! * subtransactions as committed, and only *after* marking the toplevel
! * parent as committed. Otherwise there is a race condition against
! * TransactionIdDidCommit.
*/
void
! TransactionIdCommitTree(int nxids, TransactionId *xids)
{
! if (nxids > 0)
! TransactionLogMultiUpdate(nxids, xids, TRANSACTION_STATUS_COMMITTED,
! InvalidXLogRecPtr);
}
/*
--- 250,271 ----
return false;
}
/*
* TransactionIdCommitTree
! * Marks the given transaction and children as committed
*
! * "xid" is a toplevel transaction commit, and the xids array contains its
! * committed subtransactions.
! *
! * This commit operation is not guaranteed to be atomic, but if not, subxids
! * are correctly marked subcommit first.
*/
void
! TransactionIdCommitTree(TransactionId xid, int nxids, TransactionId *xids)
{
! return TransactionIdSetTreeStatus(xid, nxids, xids,
! TRANSACTION_STATUS_COMMITTED,
! InvalidXLogRecPtr);
}
/*
*************** TransactionIdCommitTree(int nxids, Trans
*** 364,392 ****
* Same as above, but for async commits. The commit record LSN is needed.
*/
void
! TransactionIdAsyncCommitTree(int nxids, TransactionId *xids, XLogRecPtr lsn)
{
! if (nxids > 0)
! TransactionLogMultiUpdate(nxids, xids, TRANSACTION_STATUS_COMMITTED,
! lsn);
}
/*
* TransactionIdAbortTree
! * Marks all the given transaction ids as aborted.
*
* We don't need to worry about the non-atomic behavior, since any onlookers
* will consider all the xacts as not-yet-committed anyway.
*/
void
! TransactionIdAbortTree(int nxids, TransactionId *xids)
{
! if (nxids > 0)
! TransactionLogMultiUpdate(nxids, xids, TRANSACTION_STATUS_ABORTED,
! InvalidXLogRecPtr);
}
-
/*
* TransactionIdPrecedes --- is id1 logically < id2?
*/
--- 273,302 ----
* Same as above, but for async commits. The commit record LSN is needed.
*/
void
! TransactionIdAsyncCommitTree(TransactionId xid, int nxids, TransactionId *xids,
! XLogRecPtr lsn)
{
! return TransactionIdSetTreeStatus(xid, nxids, xids,
! TRANSACTION_STATUS_COMMITTED, lsn);
}
/*
* TransactionIdAbortTree
! * Marks the given transaction and children as aborted.
! *
! * "xid" is a toplevel transaction commit, and the xids array contains its
! * committed subtransactions.
*
* We don't need to worry about the non-atomic behavior, since any onlookers
* will consider all the xacts as not-yet-committed anyway.
*/
void
! TransactionIdAbortTree(TransactionId xid, int nxids, TransactionId *xids)
{
! TransactionIdSetTreeStatus(xid, nxids, xids,
! TRANSACTION_STATUS_ABORTED, InvalidXLogRecPtr);
}
/*
* TransactionIdPrecedes --- is id1 logically < id2?
*/
Index: src/backend/access/transam/twophase.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/access/transam/twophase.c,v
retrieving revision 1.45
diff -c -p -r1.45 twophase.c
*** src/backend/access/transam/twophase.c 11 Aug 2008 11:05:10 -0000 1.45
--- src/backend/access/transam/twophase.c 5 Oct 2008 18:33:40 -0000
*************** RecordTransactionCommitPrepared(Transact
*** 1745,1753 ****
XLogFlush(recptr);
/* Mark the transaction committed in pg_clog */
! TransactionIdCommit(xid);
! /* to avoid race conditions, the parent must commit first */
! TransactionIdCommitTree(nchildren, children);
/* Checkpoint can proceed now */
MyProc->inCommit = false;
--- 1745,1751 ----
XLogFlush(recptr);
/* Mark the transaction committed in pg_clog */
! TransactionIdCommitTree(xid, nchildren, children);
/* Checkpoint can proceed now */
MyProc->inCommit = false;
*************** RecordTransactionAbortPrepared(Transacti
*** 1822,1829 ****
* Mark the transaction aborted in clog. This is not absolutely necessary
* but we may as well do it while we are here.
*/
! TransactionIdAbort(xid);
! TransactionIdAbortTree(nchildren, children);
END_CRIT_SECTION();
}
--- 1820,1826 ----
* Mark the transaction aborted in clog. This is not absolutely necessary
* but we may as well do it while we are here.
*/
! TransactionIdAbortTree(xid, nchildren, children);
END_CRIT_SECTION();
}
Index: src/backend/access/transam/xact.c
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/backend/access/transam/xact.c,v
retrieving revision 1.265
diff -c -p -r1.265 xact.c
*** src/backend/access/transam/xact.c 11 Aug 2008 11:05:10 -0000 1.265
--- src/backend/access/transam/xact.c 5 Oct 2008 18:49:21 -0000
*************** static void CommitTransaction(void);
*** 254,260 ****
static TransactionId RecordTransactionAbort(bool isSubXact);
static void StartTransaction(void);
- static void RecordSubTransactionCommit(void);
static void StartSubTransaction(void);
static void CommitSubTransaction(void);
static void AbortSubTransaction(void);
--- 254,259 ----
*************** RecordTransactionCommit(void)
*** 952,962 ****
* Now we may update the CLOG, if we wrote a COMMIT record above
*/
if (markXidCommitted)
! {
! TransactionIdCommit(xid);
! /* to avoid race conditions, the parent must commit first */
! TransactionIdCommitTree(nchildren, children);
! }
}
else
{
--- 951,957 ----
* Now we may update the CLOG, if we wrote a COMMIT record above
*/
if (markXidCommitted)
! TransactionIdCommitTree(xid, nchildren, children);
}
else
{
*************** RecordTransactionCommit(void)
*** 974,984 ****
* flushed before the CLOG may be updated.
*/
if (markXidCommitted)
! {
! TransactionIdAsyncCommit(xid, XactLastRecEnd);
! /* to avoid race conditions, the parent must commit first */
! TransactionIdAsyncCommitTree(nchildren, children, XactLastRecEnd);
! }
}
/*
--- 969,975 ----
* flushed before the CLOG may be updated.
*/
if (markXidCommitted)
! TransactionIdAsyncCommitTree(xid, nchildren, children, XactLastRecEnd);
}
/*
*************** AtSubCommit_childXids(void)
*** 1156,1191 ****
s->maxChildXids = 0;
}
- /*
- * RecordSubTransactionCommit
- */
- static void
- RecordSubTransactionCommit(void)
- {
- TransactionId xid = GetCurrentTransactionIdIfAny();
-
- /*
- * We do not log the subcommit in XLOG; it doesn't matter until the
- * top-level transaction commits.
- *
- * We must mark the subtransaction subcommitted in the CLOG if it had a
- * valid XID assigned. If it did not, nobody else will ever know about
- * the existence of this subxact. We don't have to deal with deletions
- * scheduled for on-commit here, since they'll be reassigned to our parent
- * (who might still abort).
- */
- if (TransactionIdIsValid(xid))
- {
- /* XXX does this really need to be a critical section? */
- START_CRIT_SECTION();
-
- /* Record subtransaction subcommit */
- TransactionIdSubCommit(xid);
-
- END_CRIT_SECTION();
- }
- }
-
/* ----------------------------------------------------------------
* AbortTransaction stuff
* ----------------------------------------------------------------
--- 1147,1152 ----
*************** RecordTransactionAbort(bool isSubXact)
*** 1288,1301 ****
* waiting for already-aborted subtransactions. It is OK to do it without
* having flushed the ABORT record to disk, because in event of a crash
* we'd be assumed to have aborted anyway.
- *
- * The ordering here isn't critical but it seems best to mark the parent
- * first. This assures an atomic transition of all the subtransactions to
- * aborted state from the point of view of concurrent
- * TransactionIdDidAbort calls.
*/
! TransactionIdAbort(xid);
! TransactionIdAbortTree(nchildren, children);
END_CRIT_SECTION();
--- 1249,1256 ----
* waiting for already-aborted subtransactions. It is OK to do it without
* having flushed the ABORT record to disk, because in event of a crash
* we'd be assumed to have aborted anyway.
*/
! TransactionIdAbortTree(xid, nchildren, children);
END_CRIT_SECTION();
*************** CommitSubTransaction(void)
*** 3791,3798 ****
/* Must CCI to ensure commands of subtransaction are seen as done */
CommandCounterIncrement();
! /* Mark subtransaction as subcommitted */
! RecordSubTransactionCommit();
/* Post-commit cleanup */
if (TransactionIdIsValid(s->transactionId))
--- 3746,3757 ----
/* Must CCI to ensure commands of subtransaction are seen as done */
CommandCounterIncrement();
! /*
! * Prior to 8.4 we marked subcommit in clog at this point.
! * We now only perform that step, if required, as part of the
! * atomic update of the whole transaction tree at top level
! * commit or abort.
! */
/* Post-commit cleanup */
if (TransactionIdIsValid(s->transactionId))
*************** xact_redo_commit(xl_xact_commit *xlrec,
*** 4259,4269 ****
TransactionId max_xid;
int i;
! TransactionIdCommit(xid);
!
! /* Mark committed subtransactions as committed */
sub_xids = (TransactionId *) &(xlrec->xnodes[xlrec->nrels]);
! TransactionIdCommitTree(xlrec->nsubxacts, sub_xids);
/* Make sure nextXid is beyond any XID mentioned in the record */
max_xid = xid;
--- 4218,4226 ----
TransactionId max_xid;
int i;
! /* Mark the transaction committed in pg_clog */
sub_xids = (TransactionId *) &(xlrec->xnodes[xlrec->nrels]);
! TransactionIdCommitTree(xid, xlrec->nsubxacts, sub_xids);
/* Make sure nextXid is beyond any XID mentioned in the record */
max_xid = xid;
*************** xact_redo_abort(xl_xact_abort *xlrec, Tr
*** 4299,4309 ****
TransactionId max_xid;
int i;
! TransactionIdAbort(xid);
!
! /* Mark subtransactions as aborted */
sub_xids = (TransactionId *) &(xlrec->xnodes[xlrec->nrels]);
! TransactionIdAbortTree(xlrec->nsubxacts, sub_xids);
/* Make sure nextXid is beyond any XID mentioned in the record */
max_xid = xid;
--- 4256,4264 ----
TransactionId max_xid;
int i;
! /* Mark the transaction aborted in pg_clog */
sub_xids = (TransactionId *) &(xlrec->xnodes[xlrec->nrels]);
! TransactionIdAbortTree(xid, xlrec->nsubxacts, sub_xids);
/* Make sure nextXid is beyond any XID mentioned in the record */
max_xid = xid;
Index: src/include/access/clog.h
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/include/access/clog.h,v
retrieving revision 1.21
diff -c -p -r1.21 clog.h
*** src/include/access/clog.h 1 Jan 2008 19:45:56 -0000 1.21
--- src/include/access/clog.h 5 Oct 2008 18:33:40 -0000
*************** typedef int XidStatus;
*** 32,38 ****
#define NUM_CLOG_BUFFERS 8
! extern void TransactionIdSetStatus(TransactionId xid, XidStatus status, XLogRecPtr lsn);
extern XidStatus TransactionIdGetStatus(TransactionId xid, XLogRecPtr *lsn);
extern Size CLOGShmemSize(void);
--- 32,39 ----
#define NUM_CLOG_BUFFERS 8
! extern void TransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
! TransactionId *subxids, XidStatus status, XLogRecPtr lsn);
extern XidStatus TransactionIdGetStatus(TransactionId xid, XLogRecPtr *lsn);
extern Size CLOGShmemSize(void);
Index: src/include/access/transam.h
===================================================================
RCS file: /home/alvherre/Code/cvs/pgsql/src/include/access/transam.h,v
retrieving revision 1.65
diff -c -p -r1.65 transam.h
*** src/include/access/transam.h 11 Mar 2008 20:20:35 -0000 1.65
--- src/include/access/transam.h 5 Oct 2008 18:33:40 -0000
*************** extern VariableCache ShmemVariableCache;
*** 139,151 ****
extern bool TransactionIdDidCommit(TransactionId transactionId);
extern bool TransactionIdDidAbort(TransactionId transactionId);
extern bool TransactionIdIsKnownCompleted(TransactionId transactionId);
- extern void TransactionIdCommit(TransactionId transactionId);
- extern void TransactionIdAsyncCommit(TransactionId transactionId, XLogRecPtr lsn);
extern void TransactionIdAbort(TransactionId transactionId);
! extern void TransactionIdSubCommit(TransactionId transactionId);
! extern void TransactionIdCommitTree(int nxids, TransactionId *xids);
! extern void TransactionIdAsyncCommitTree(int nxids, TransactionId *xids, XLogRecPtr lsn);
! extern void TransactionIdAbortTree(int nxids, TransactionId *xids);
extern bool TransactionIdPrecedes(TransactionId id1, TransactionId id2);
extern bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2);
extern bool TransactionIdFollows(TransactionId id1, TransactionId id2);
--- 139,148 ----
extern bool TransactionIdDidCommit(TransactionId transactionId);
extern bool TransactionIdDidAbort(TransactionId transactionId);
extern bool TransactionIdIsKnownCompleted(TransactionId transactionId);
extern void TransactionIdAbort(TransactionId transactionId);
! extern void TransactionIdCommitTree(TransactionId xid, int nxids, TransactionId *xids);
! extern void TransactionIdAsyncCommitTree(TransactionId xid, int nxids, TransactionId *xids, XLogRecPtr lsn);
! extern void TransactionIdAbortTree(TransactionId xid, int nxids, TransactionId *xids);
extern bool TransactionIdPrecedes(TransactionId id1, TransactionId id2);
extern bool TransactionIdPrecedesOrEquals(TransactionId id1, TransactionId id2);
extern bool TransactionIdFollows(TransactionId id1, TransactionId id2);
--
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