0011-wal_decoding-Add-alreadyLocked-parameter-to-GetOldes.patch

>From 54cf27b505efcf5aeeb2b78638e88fab04e66b5b Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Thu, 13 Dec 2012 20:47:57 +0100
Subject: [PATCH 11/19] wal_decoding: Add alreadyLocked parameter to
 GetOldestXminNoLock

This is useful because it allows to compute the current OldestXmin while
already holding the procarray lock which enables setting the own xmin horizon
safely.
---
 src/backend/access/transam/xlog.c     |  4 ++--
 src/backend/catalog/index.c           |  3 ++-
 src/backend/commands/analyze.c        |  2 +-
 src/backend/commands/vacuum.c         |  4 ++--
 src/backend/replication/walreceiver.c |  2 +-
 src/backend/storage/ipc/procarray.c   | 16 ++++++++--------
 src/include/storage/procarray.h       |  2 +-
 7 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 310a654..ab7f0e4 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6823,7 +6823,7 @@ CreateCheckPoint(int flags)
 	 * StartupSUBTRANS hasn't been called yet.
 	 */
 	if (!RecoveryInProgress())
-		TruncateSUBTRANS(GetOldestXmin(true, false));
+		TruncateSUBTRANS(GetOldestXmin(true, false, false));
 
 	/* Real work is done, but log and update stats before releasing lock. */
 	LogCheckpointEnd(false);
@@ -7107,7 +7107,7 @@ CreateRestartPoint(int flags)
 	 * this because StartupSUBTRANS hasn't been called yet.
 	 */
 	if (EnableHotStandby)
-		TruncateSUBTRANS(GetOldestXmin(true, false));
+		TruncateSUBTRANS(GetOldestXmin(true, false, false));
 
 	/* Real work is done, but log and update before releasing lock. */
 	LogCheckpointEnd(true);
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index a29c106..dbee4d5 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2196,7 +2196,8 @@ IndexBuildHeapScan(Relation heapRelation,
 	{
 		snapshot = SnapshotAny;
 		/* okay to ignore lazy VACUUMs here */
-		OldestXmin = GetOldestXmin(heapRelation->rd_rel->relisshared, true);
+		OldestXmin = GetOldestXmin(heapRelation->rd_rel->relisshared, true,
+								   false);
 	}
 
 	scan = heap_beginscan_strat(heapRelation,	/* relation */
diff --git a/src/backend/commands/analyze.c b/src/backend/commands/analyze.c
index ac16284..f5a6af7 100644
--- a/src/backend/commands/analyze.c
+++ b/src/backend/commands/analyze.c
@@ -1077,7 +1077,7 @@ acquire_sample_rows(Relation onerel, int elevel,
 	totalblocks = RelationGetNumberOfBlocks(onerel);
 
 	/* Need a cutoff xmin for HeapTupleSatisfiesVacuum */
-	OldestXmin = GetOldestXmin(onerel->rd_rel->relisshared, true);
+	OldestXmin = GetOldestXmin(onerel->rd_rel->relisshared, true, false);
 
 	/* Prepare for sampling block numbers */
 	BlockSampler_Init(&bs, totalblocks, targrows);
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 2d3170a..158d0dc 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -394,7 +394,7 @@ vacuum_set_xid_limits(int freeze_min_age,
 	 * working on a particular table at any time, and that each vacuum is
 	 * always an independent transaction.
 	 */
-	*oldestXmin = GetOldestXmin(sharedRel, true);
+	*oldestXmin = GetOldestXmin(sharedRel, true, false);
 
 	Assert(TransactionIdIsNormal(*oldestXmin));
 
@@ -686,7 +686,7 @@ vac_update_datfrozenxid(void)
 	 * committed pg_class entries for new tables; see AddNewRelationTuple().
 	 * Se we cannot produce a wrong minimum by starting with this.
 	 */
-	newFrozenXid = GetOldestXmin(true, true);
+	newFrozenXid = GetOldestXmin(true, true, false);
 
 	/*
 	 * We must seqscan pg_class to find the minimum Xid, because there is no
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 16cf944..2b77369 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -1089,7 +1089,7 @@ XLogWalRcvSendHSFeedback(void)
 	 * Make the expensive call to get the oldest xmin once we are certain
 	 * everything else has been checked.
 	 */
-	xmin = GetOldestXmin(true, false);
+	xmin = GetOldestXmin(true, false, false);
 
 	/*
 	 * Get epoch and adjust if nextXid and oldestXmin are different sides of
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 4308128..f59e792 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -1100,7 +1100,7 @@ TransactionIdIsActive(TransactionId xid)
  * GetOldestXmin() move backwards, with no consequences for data integrity.
  */
 TransactionId
-GetOldestXmin(bool allDbs, bool ignoreVacuum)
+GetOldestXmin(bool allDbs, bool ignoreVacuum, bool alreadyLocked)
 {
 	ProcArrayStruct *arrayP = procArray;
 	TransactionId result;
@@ -1109,7 +1109,8 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
 	/* Cannot look for individual databases during recovery */
 	Assert(allDbs || !RecoveryInProgress());
 
-	LWLockAcquire(ProcArrayLock, LW_SHARED);
+	if (!alreadyLocked)
+		LWLockAcquire(ProcArrayLock, LW_SHARED);
 
 	/*
 	 * We initialize the MIN() calculation with latestCompletedXid + 1. This
@@ -1164,7 +1165,8 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
 		 */
 		TransactionId kaxmin = KnownAssignedXidsGetOldestXmin();
 
-		LWLockRelease(ProcArrayLock);
+		if (!alreadyLocked)
+			LWLockRelease(ProcArrayLock);
 
 		if (TransactionIdIsNormal(kaxmin) &&
 			TransactionIdPrecedes(kaxmin, result))
@@ -1172,10 +1174,8 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
 	}
 	else
 	{
-		/*
-		 * No other information needed, so release the lock immediately.
-		 */
-		LWLockRelease(ProcArrayLock);
+		if (!alreadyLocked)
+			LWLockRelease(ProcArrayLock);
 
 		/*
 		 * Compute the cutoff XID by subtracting vacuum_defer_cleanup_age,
@@ -1249,7 +1249,7 @@ GetMaxSnapshotSubxidCount(void)
  *			older than this are known not running any more.
  *		RecentGlobalXmin: the global xmin (oldest TransactionXmin across all
  *			running transactions, except those running LAZY VACUUM).  This is
- *			the same computation done by GetOldestXmin(true, true).
+ *			the same computation done by GetOldestXmin(true, true, ...).
  *
  * Note: this function should probably not be called with an argument that's
  * not statically allocated (see xip allocation below).
diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h
index d5fdfea..fe0bad7 100644
--- a/src/include/storage/procarray.h
+++ b/src/include/storage/procarray.h
@@ -49,7 +49,7 @@ extern RunningTransactions GetRunningTransactionData(void);
 
 extern bool TransactionIdIsInProgress(TransactionId xid);
 extern bool TransactionIdIsActive(TransactionId xid);
-extern TransactionId GetOldestXmin(bool allDbs, bool ignoreVacuum);
+extern TransactionId GetOldestXmin(bool allDbs, bool ignoreVacuum, bool alreadyLocked);
 extern TransactionId GetOldestActiveTransactionId(void);
 
 extern VirtualTransactionId *GetVirtualXIDsDelayingChkpt(int *nvxids);
-- 
1.7.12.289.g0ce9864.dirty