From aae52b88ce67adc0261ebfeafb8496ed9e88d240 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Tue, 13 Aug 2024 16:40:57 +0300 Subject: [PATCH 4/5] Remove the now-unused xids array from xl_running_xacts We still generate running-xacts records, because they are still needed to initialize the snapshot in logical decoding. --- src/backend/access/rmgrdesc/standbydesc.c | 18 ------------ src/backend/replication/logical/snapbuild.c | 8 +++--- src/backend/storage/ipc/standby.c | 32 +++++---------------- src/include/storage/standby.h | 2 -- src/include/storage/standbydefs.h | 16 +++++++---- 5 files changed, 21 insertions(+), 55 deletions(-) diff --git a/src/backend/access/rmgrdesc/standbydesc.c b/src/backend/access/rmgrdesc/standbydesc.c index 32e509a4006..99f08beb4a8 100644 --- a/src/backend/access/rmgrdesc/standbydesc.c +++ b/src/backend/access/rmgrdesc/standbydesc.c @@ -19,28 +19,10 @@ static void standby_desc_running_xacts(StringInfo buf, xl_running_xacts *xlrec) { - int i; - appendStringInfo(buf, "nextXid %u latestCompletedXid %u oldestRunningXid %u", xlrec->nextXid, xlrec->latestCompletedXid, xlrec->oldestRunningXid); - if (xlrec->xcnt > 0) - { - appendStringInfo(buf, "; %d xacts:", xlrec->xcnt); - for (i = 0; i < xlrec->xcnt; i++) - appendStringInfo(buf, " %u", xlrec->xids[i]); - } - - if (xlrec->subxid_overflow) - appendStringInfoString(buf, "; subxid overflowed"); - - if (xlrec->subxcnt > 0) - { - appendStringInfo(buf, "; %d subxacts:", xlrec->subxcnt); - for (i = 0; i < xlrec->subxcnt; i++) - appendStringInfo(buf, " %u", xlrec->xids[xlrec->xcnt + i]); - } } void diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c index 31da0832cc3..cac3ffe577e 100644 --- a/src/backend/replication/logical/snapbuild.c +++ b/src/backend/replication/logical/snapbuild.c @@ -1316,8 +1316,8 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn ereport(LOG, (errmsg("logical decoding found initial starting point at %X/%X", LSN_FORMAT_ARGS(lsn)), - errdetail("Waiting for transactions (approximately %d) older than %u to end.", - running->xcnt, running->nextXid))); + errdetail("Waiting for transactions older than %u to end.", + running->nextXid))); SnapBuildWaitSnapshot(running->nextXid); } @@ -1340,8 +1340,8 @@ SnapBuildFindSnapshot(SnapBuild *builder, XLogRecPtr lsn, xl_running_xacts *runn ereport(LOG, (errmsg("logical decoding found initial consistent point at %X/%X", LSN_FORMAT_ARGS(lsn)), - errdetail("Waiting for transactions (approximately %d) older than %u to end.", - running->xcnt, running->nextXid))); + errdetail("Waiting for transactions older than %u to end.", + running->nextXid))); SnapBuildWaitSnapshot(running->nextXid); } diff --git a/src/backend/storage/ipc/standby.c b/src/backend/storage/ipc/standby.c index e02c9ab842d..6ed46bed033 100644 --- a/src/backend/storage/ipc/standby.c +++ b/src/backend/storage/ipc/standby.c @@ -1337,9 +1337,6 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) xl_running_xacts xlrec; XLogRecPtr recptr; - xlrec.xcnt = CurrRunningXacts->xcnt; - xlrec.subxcnt = CurrRunningXacts->subxcnt; - xlrec.subxid_overflow = (CurrRunningXacts->subxid_status != SUBXIDS_IN_ARRAY); xlrec.nextXid = CurrRunningXacts->nextXid; xlrec.oldestRunningXid = CurrRunningXacts->oldestRunningXid; xlrec.latestCompletedXid = CurrRunningXacts->latestCompletedXid; @@ -1347,31 +1344,16 @@ LogCurrentRunningXacts(RunningTransactions CurrRunningXacts) /* Header */ XLogBeginInsert(); XLogSetRecordFlags(XLOG_MARK_UNIMPORTANT); - XLogRegisterData((char *) (&xlrec), MinSizeOfXactRunningXacts); - - /* array of TransactionIds */ - if (xlrec.xcnt > 0) - XLogRegisterData((char *) CurrRunningXacts->xids, - (xlrec.xcnt + xlrec.subxcnt) * sizeof(TransactionId)); + XLogRegisterData((char *) (&xlrec), SizeOfXactRunningXacts); recptr = XLogInsert(RM_STANDBY_ID, XLOG_RUNNING_XACTS); - if (xlrec.subxid_overflow) - elog(DEBUG2, - "snapshot of %d running transactions overflowed (lsn %X/%X oldest xid %u latest complete %u next xid %u)", - CurrRunningXacts->xcnt, - LSN_FORMAT_ARGS(recptr), - CurrRunningXacts->oldestRunningXid, - CurrRunningXacts->latestCompletedXid, - CurrRunningXacts->nextXid); - else - elog(DEBUG2, - "snapshot of %d+%d running transaction ids (lsn %X/%X oldest xid %u latest complete %u next xid %u)", - CurrRunningXacts->xcnt, CurrRunningXacts->subxcnt, - LSN_FORMAT_ARGS(recptr), - CurrRunningXacts->oldestRunningXid, - CurrRunningXacts->latestCompletedXid, - CurrRunningXacts->nextXid); + elog(DEBUG2, + "logging running transaction bounds (lsn %X/%X oldest xid %u latest complete %u next xid %u)", + LSN_FORMAT_ARGS(recptr), + CurrRunningXacts->oldestRunningXid, + CurrRunningXacts->latestCompletedXid, + CurrRunningXacts->nextXid); /* * Ensure running_xacts information is synced to disk not too far in the diff --git a/src/include/storage/standby.h b/src/include/storage/standby.h index cce0bc521e7..9d5a298a392 100644 --- a/src/include/storage/standby.h +++ b/src/include/storage/standby.h @@ -60,8 +60,6 @@ extern void StandbyReleaseLockTree(TransactionId xid, extern void StandbyReleaseAllLocks(void); extern void StandbyReleaseOldLocks(TransactionId oldxid); -#define MinSizeOfXactRunningXacts offsetof(xl_running_xacts, xids) - /* * Declarations for GetRunningTransactionData(). Similar to Snapshots, but diff --git a/src/include/storage/standbydefs.h b/src/include/storage/standbydefs.h index fe12f463a86..d8582094472 100644 --- a/src/include/storage/standbydefs.h +++ b/src/include/storage/standbydefs.h @@ -42,20 +42,24 @@ typedef struct xl_standby_locks } xl_standby_locks; /* - * When we write running xact data to WAL, we use this structure. + * Data included in an XLOG_RUNNING_XACTS record. + * + * This used to include a list of running XIDs, hence the name, but nowadays + * this only contains the min and max bounds of the transactions that were + * running when the record was written. They are needed to initialize logical + * decoding. They are also used in hot standby to prune information about old + * running transactions, in case the the primary didn't write a COMMIT/ABORT + * record for some reason. */ typedef struct xl_running_xacts { - int xcnt; /* # of xact ids in xids[] */ - int subxcnt; /* # of subxact ids in xids[] */ - bool subxid_overflow; /* snapshot overflowed, subxids missing */ TransactionId nextXid; /* xid from TransamVariables->nextXid */ TransactionId oldestRunningXid; /* *not* oldestXmin */ TransactionId latestCompletedXid; /* so we can set xmax */ - - TransactionId xids[FLEXIBLE_ARRAY_MEMBER]; } xl_running_xacts; +#define SizeOfXactRunningXacts sizeof(xl_running_xacts) + /* * Invalidations for standby, currently only when transactions without an * assigned xid commit. -- 2.39.5