From 06da3c570f21394003fc392d80f54862f7dec19f Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Mon, 20 Oct 2008 19:18:18 +0000
Subject: [PATCH] Rework subtransaction commit protocol for hot standby.
This patch eliminates the marking of subtransactions as SUBCOMMITTED in pg_clog
during their commit; instead they remain in-progress until main transaction
commit. At main transaction commit, the commit protocol is atomic-by-page
instead of one transaction at a time. To avoid a race condition with some
subtransactions appearing committed before others in the case where they span
more than one pg_clog page, we conserve the logic that marks them subcommitted
before marking the parent committed.
Simon Riggs with minor help from me
---
src/backend/access/transam/README | 21 ++-
src/backend/access/transam/clog.c | 229 ++++++++++++++++++++++++--
src/backend/access/transam/transam.c | 144 +++-------------
src/backend/access/transam/twophase.c | 9 +-
src/backend/access/transam/xact.c | 72 ++------
src/include/access/clog.h | 5 +-
src/include/access/transam.h | 11 +-
7 files changed, 279 insertions(+), 212 deletions(-)
diff --git a/src/backend/access/transam/README b/src/backend/access/transam/README
index 2288102d40c..2edac9d088f 100644
--- a/src/backend/access/transam/README
+++ b/src/backend/access/transam/README
@@ -1,4 +1,4 @@
-$PostgreSQL: pgsql/src/backend/access/transam/README,v 1.11 2008/03/21 13:23:28 momjian Exp $
+$PostgreSQL: pgsql/src/backend/access/transam/README,v 1.12 2008/10/20 19:18:18 alvherre Exp $
The Transaction System
======================
@@ -341,11 +341,20 @@ from disk. They also allow information to be permanent across server restarts.
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.
+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 transitory 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
diff --git a/src/backend/access/transam/clog.c b/src/backend/access/transam/clog.c
index f30ef3a2262..fcff3ea3cfd 100644
--- a/src/backend/access/transam/clog.c
+++ b/src/backend/access/transam/clog.c
@@ -26,7 +26,7 @@
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.47 2008/08/01 13:16:08 alvherre Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/clog.c,v 1.48 2008/10/20 19:18:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -80,32 +80,182 @@ static int ZeroCLOGPage(int pageno, bool writeXlog);
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);
+static void TransactionIdSetStatusBit(TransactionId xid, XidStatus status,
+ XLogRecPtr lsn, int slotno);
+static void set_status_by_pages(int nsubxids, TransactionId *subxids,
+ XidStatus status, XLogRecPtr lsn);
/*
- * Record the final state of a transaction in the commit log.
+ * 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.
+ *
+ * Example:
+ * TransactionId t commits and has subxids t1, t2, t3, t4
+ * t is on page p1, t1 is also on p1, t2 and t3 are on p2, t4 is on p3
+ * 1. update pages2-3:
+ * page2: set t2,t3 as sub-committed
+ * page3: set t4 as sub-committed
+ * 2. update page1:
+ * set t1 as sub-committed,
+ * then set t as committed,
+ then set t1 as committed
+ * 3. update pages2-3:
+ * page2: set t2,t3 as committed
+ * page3: set t4 as committed
+ *
* 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.
+ * 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
-TransactionIdSetStatus(TransactionId xid, XidStatus status, XLogRecPtr lsn)
+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);
+ }
+ else
+ {
+ int nsubxids_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
+ * for the subxids on that first page.
+ */
+ if (status == TRANSACTION_STATUS_COMMITTED)
+ set_status_by_pages(nsubxids - nsubxids_on_first_page,
+ subxids + nsubxids_on_first_page,
+ TRANSACTION_STATUS_SUB_COMMITTED, lsn);
+
+ /*
+ * Now set the parent and subtransactions on same page as the parent,
+ * if any
+ */
+ pageno = TransactionIdToPage(xid);
+ TransactionIdSetPageStatus(xid, nsubxids_on_first_page, subxids, status,
+ lsn, pageno);
+
+ /*
+ * 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_status_by_pages(nsubxids - nsubxids_on_first_page,
+ subxids + nsubxids_on_first_page,
+ status, lsn);
+ }
+}
+
+/*
+ * Helper for TransactionIdSetTreeStatus: set the status for a bunch of
+ * transactions, chunking in the separate CLOG pages involved. We never
+ * pass the whole transaction tree to this function, only subtransactions
+ * that are on different pages to the top level transaction id.
+ */
+static void
+set_status_by_pages(int nsubxids, TransactionId *subxids,
+ XidStatus status, XLogRecPtr lsn)
+{
+ 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);
+ 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()
+ */
+static void
+TransactionIdSetPageStatus(TransactionId xid, int nsubxids,
+ TransactionId *subxids, XidStatus status,
+ XLogRecPtr lsn, int pageno)
{
- int pageno = TransactionIdToPage(xid);
- int byteno = TransactionIdToByte(xid);
- int bshift = TransactionIdToBIndex(xid) * CLOG_BITS_PER_XACT;
int slotno;
- char *byteptr;
- char byteval;
+ int i;
Assert(status == TRANSACTION_STATUS_COMMITTED ||
status == TRANSACTION_STATUS_ABORTED ||
- status == TRANSACTION_STATUS_SUB_COMMITTED);
+ (status == TRANSACTION_STATUS_SUB_COMMITTED && !TransactionIdIsValid(xid)));
LWLockAcquire(CLogControlLock, LW_EXCLUSIVE);
@@ -116,9 +266,62 @@ TransactionIdSetStatus(TransactionId xid, XidStatus status, XLogRecPtr lsn)
* 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).
+ * we think.
*/
slotno = SimpleLruReadPage(ClogCtl, pageno, XLogRecPtrIsInvalid(lsn), xid);
+
+ /*
+ * Set the main transaction id, if any.
+ *
+ * If we update 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.
+ * If we are updating commits on the page with the top-level xid that could
+ * break atomicity, so we subcommit the subxids first before we mark the
+ * top-level commit.
+ */
+ if (TransactionIdIsValid(xid))
+ {
+ /* Subtransactions first, if needed ... */
+ if (status == TRANSACTION_STATUS_COMMITTED)
+ {
+ for (i = 0; i < nsubxids; i++)
+ {
+ Assert(ClogCtl->shared->page_number[slotno] == TransactionIdToPage(subxids[i]));
+ TransactionIdSetStatusBit(subxids[i],
+ TRANSACTION_STATUS_SUB_COMMITTED,
+ lsn, slotno);
+ }
+ }
+
+ /* ... then the main transaction */
+ 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 */
@@ -132,8 +335,6 @@ TransactionIdSetStatus(TransactionId xid, XidStatus status, XLogRecPtr lsn)
byteval |= (status << bshift);
*byteptr = byteval;
- ClogCtl->shared->page_dirty[slotno] = true;
-
/*
* Update the group LSN if the transaction completion LSN is higher.
*
@@ -149,8 +350,6 @@ TransactionIdSetStatus(TransactionId xid, XidStatus status, XLogRecPtr lsn)
if (XLByteLT(ClogCtl->shared->group_lsn[lsnindex], lsn))
ClogCtl->shared->group_lsn[lsnindex] = lsn;
}
-
- LWLockRelease(CLogControlLock);
}
/*
diff --git a/src/backend/access/transam/transam.c b/src/backend/access/transam/transam.c
index 6fbaf7158c2..0e74dd446e7 100644
--- a/src/backend/access/transam/transam.c
+++ b/src/backend/access/transam/transam.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/transam/transam.c,v 1.76 2008/03/26 18:48:59 alvherre Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/transam.c,v 1.77 2008/10/20 19:18:18 alvherre Exp $
*
* NOTES
* This file contains the high level access-method interface to the
@@ -40,15 +40,12 @@ static const XLogRecPtr InvalidXLogRecPtr = {0, 0};
/* Local functions */
static XidStatus TransactionLogFetch(TransactionId transactionId);
-static void TransactionLogUpdate(TransactionId transactionId,
- XidStatus status, XLogRecPtr lsn);
/* ----------------------------------------------------------------
* Postgres log access method interface
*
* TransactionLogFetch
- * TransactionLogUpdate
* ----------------------------------------------------------------
*/
@@ -100,41 +97,6 @@ TransactionLogFetch(TransactionId transactionId)
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
*
@@ -144,11 +106,12 @@ TransactionLogMultiUpdate(int nxids, TransactionId *xids,
* these functions test the transaction status of
* a specified transaction id.
*
- * TransactionIdCommit
- * TransactionIdAbort
+ * TransactionIdCommitTree
+ * TransactionIdAsyncCommitTree
+ * TransactionIdAbortTree
* ========
- * these functions set the transaction status
- * of the specified xid.
+ * 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.
@@ -287,76 +250,22 @@ TransactionIdIsKnownCompleted(TransactionId transactionId)
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.
+ * Marks the given transaction and children 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.
+ * "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(int nxids, TransactionId *xids)
+TransactionIdCommitTree(TransactionId xid, int nxids, TransactionId *xids)
{
- if (nxids > 0)
- TransactionLogMultiUpdate(nxids, xids, TRANSACTION_STATUS_COMMITTED,
- InvalidXLogRecPtr);
+ return TransactionIdSetTreeStatus(xid, nxids, xids,
+ TRANSACTION_STATUS_COMMITTED,
+ InvalidXLogRecPtr);
}
/*
@@ -364,29 +273,30 @@ TransactionIdCommitTree(int nxids, TransactionId *xids)
* Same as above, but for async commits. The commit record LSN is needed.
*/
void
-TransactionIdAsyncCommitTree(int nxids, TransactionId *xids, XLogRecPtr lsn)
+TransactionIdAsyncCommitTree(TransactionId xid, int nxids, TransactionId *xids,
+ XLogRecPtr lsn)
{
- if (nxids > 0)
- TransactionLogMultiUpdate(nxids, xids, TRANSACTION_STATUS_COMMITTED,
- lsn);
+ return TransactionIdSetTreeStatus(xid, nxids, xids,
+ TRANSACTION_STATUS_COMMITTED, lsn);
}
/*
* TransactionIdAbortTree
- * Marks all the given transaction ids as aborted.
+ * 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(int nxids, TransactionId *xids)
+TransactionIdAbortTree(TransactionId xid, int nxids, TransactionId *xids)
{
- if (nxids > 0)
- TransactionLogMultiUpdate(nxids, xids, TRANSACTION_STATUS_ABORTED,
- InvalidXLogRecPtr);
+ TransactionIdSetTreeStatus(xid, nxids, xids,
+ TRANSACTION_STATUS_ABORTED, InvalidXLogRecPtr);
}
-
/*
* TransactionIdPrecedes --- is id1 logically < id2?
*/
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index b86bdc36677..d24ea6b2a10 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.45 2008/08/11 11:05:10 heikki Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.46 2008/10/20 19:18:18 alvherre Exp $
*
* NOTES
* Each global transaction is associated with a global transaction
@@ -1745,9 +1745,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
XLogFlush(recptr);
/* Mark the transaction committed in pg_clog */
- TransactionIdCommit(xid);
- /* to avoid race conditions, the parent must commit first */
- TransactionIdCommitTree(nchildren, children);
+ TransactionIdCommitTree(xid, nchildren, children);
/* Checkpoint can proceed now */
MyProc->inCommit = false;
@@ -1822,8 +1820,7 @@ RecordTransactionAbortPrepared(TransactionId xid,
* 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);
+ TransactionIdAbortTree(xid, nchildren, children);
END_CRIT_SECTION();
}
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5f6c9df677a..49737dfb8b4 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.265 2008/08/11 11:05:10 heikki Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.266 2008/10/20 19:18:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -254,7 +254,6 @@ static void CommitTransaction(void);
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);
@@ -952,11 +951,7 @@ RecordTransactionCommit(void)
* 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);
- }
+ TransactionIdCommitTree(xid, nchildren, children);
}
else
{
@@ -974,11 +969,7 @@ RecordTransactionCommit(void)
* 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);
- }
+ TransactionIdAsyncCommitTree(xid, nchildren, children, XactLastRecEnd);
}
/*
@@ -1156,36 +1147,6 @@ AtSubCommit_childXids(void)
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
* ----------------------------------------------------------------
@@ -1288,14 +1249,8 @@ RecordTransactionAbort(bool isSubXact)
* 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);
+ TransactionIdAbortTree(xid, nchildren, children);
END_CRIT_SECTION();
@@ -3791,8 +3746,11 @@ CommitSubTransaction(void)
/* Must CCI to ensure commands of subtransaction are seen as done */
CommandCounterIncrement();
- /* Mark subtransaction as subcommitted */
- RecordSubTransactionCommit();
+ /*
+ * 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))
@@ -4259,11 +4217,9 @@ xact_redo_commit(xl_xact_commit *xlrec, TransactionId xid)
TransactionId max_xid;
int i;
- TransactionIdCommit(xid);
-
- /* Mark committed subtransactions as committed */
+ /* Mark the transaction committed in pg_clog */
sub_xids = (TransactionId *) &(xlrec->xnodes[xlrec->nrels]);
- TransactionIdCommitTree(xlrec->nsubxacts, sub_xids);
+ TransactionIdCommitTree(xid, xlrec->nsubxacts, sub_xids);
/* Make sure nextXid is beyond any XID mentioned in the record */
max_xid = xid;
@@ -4299,11 +4255,9 @@ xact_redo_abort(xl_xact_abort *xlrec, TransactionId xid)
TransactionId max_xid;
int i;
- TransactionIdAbort(xid);
-
- /* Mark subtransactions as aborted */
+ /* Mark the transaction aborted in pg_clog */
sub_xids = (TransactionId *) &(xlrec->xnodes[xlrec->nrels]);
- TransactionIdAbortTree(xlrec->nsubxacts, sub_xids);
+ TransactionIdAbortTree(xid, xlrec->nsubxacts, sub_xids);
/* Make sure nextXid is beyond any XID mentioned in the record */
max_xid = xid;
diff --git a/src/include/access/clog.h b/src/include/access/clog.h
index 8b640a39d6d..ac74c471320 100644
--- a/src/include/access/clog.h
+++ b/src/include/access/clog.h
@@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/access/clog.h,v 1.21 2008/01/01 19:45:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/access/clog.h,v 1.22 2008/10/20 19:18:18 alvherre Exp $
*/
#ifndef CLOG_H
#define CLOG_H
@@ -32,7 +32,8 @@ typedef int XidStatus;
#define NUM_CLOG_BUFFERS 8
-extern void TransactionIdSetStatus(TransactionId xid, XidStatus status, XLogRecPtr lsn);
+extern void TransactionIdSetTreeStatus(TransactionId xid, int nsubxids,
+ TransactionId *subxids, XidStatus status, XLogRecPtr lsn);
extern XidStatus TransactionIdGetStatus(TransactionId xid, XLogRecPtr *lsn);
extern Size CLOGShmemSize(void);
diff --git a/src/include/access/transam.h b/src/include/access/transam.h
index 232c59cad3c..6b37723cb9b 100644
--- a/src/include/access/transam.h
+++ b/src/include/access/transam.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/access/transam.h,v 1.65 2008/03/11 20:20:35 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/transam.h,v 1.66 2008/10/20 19:18:18 alvherre Exp $
*
*-------------------------------------------------------------------------
*/
@@ -139,13 +139,10 @@ extern VariableCache ShmemVariableCache;
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 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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