From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 9 Jan 2008 21:52:36 +0000 (+0000)
Subject: Fix CREATE INDEX CONCURRENTLY to not deadlock against an automatic or manual
X-Git-Url: http://waps.l3s.uni-hannover.de/gitweb/?a=commitdiff_plain;h=7e7e34da336662d9676fb673ad8305f0ba973faa;p=users%2Fbernd%2Fpostgres.git

Fix CREATE INDEX CONCURRENTLY to not deadlock against an automatic or manual
VACUUM that is blocked waiting to get lock on the table being indexed.
Per report and fix suggestion from Greg Stark.
---

diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 6d6a6d0e1a..e9d64b22f3 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -38,6 +38,7 @@
 #include "parser/parse_expr.h"
 #include "parser/parse_func.h"
 #include "parser/parsetree.h"
+#include "storage/proc.h"
 #include "storage/procarray.h"
 #include "utils/acl.h"
 #include "utils/builtins.h"
@@ -630,11 +631,19 @@ DefineIndex(RangeVar *heapRelation,
 	 * We can exclude any running transactions that have xmin >= the xmax of
 	 * our reference snapshot, since they are clearly not interested in any
 	 * missing older tuples.  Transactions in other DBs aren't a problem
-	 * either, since they'll never even be able to see this index. Also,
-	 * GetCurrentVirtualXIDs never reports our own vxid, so we need not check
-	 * for that.
+	 * either, since they'll never even be able to see this index.
+	 *
+	 * We can also exclude autovacuum processes and processes running manual
+	 * lazy VACUUMs, because they won't be fazed by missing index entries
+	 * either.  (Manual ANALYZEs, however, can't be excluded because they
+	 * might be within transactions that are going to do arbitrary operations
+	 * later.)
+	 *
+	 * Also, GetCurrentVirtualXIDs never reports our own vxid, so we need not
+	 * check for that.
 	 */
-	old_snapshots = GetCurrentVirtualXIDs(ActiveSnapshot->xmax, false);
+	old_snapshots = GetCurrentVirtualXIDs(ActiveSnapshot->xmax, false,
+										  PROC_IS_AUTOVACUUM | PROC_IN_VACUUM);
 
 	while (VirtualTransactionIdIsValid(*old_snapshots))
 	{
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index c19638b61f..69bb1614d4 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -1006,10 +1006,12 @@ IsBackendPid(int pid)
  *
  * If limitXmin is not InvalidTransactionId, we skip any backends
  * with xmin >= limitXmin.	If allDbs is false, we skip backends attached
- * to other databases.	Also, our own process is always skipped.
+ * to other databases.  If excludeVacuum isn't zero, we skip processes for
+ * which (excludeVacuum & vacuumFlags) is not zero.  Also, our own process
+ * is always skipped.
  */
 VirtualTransactionId *
-GetCurrentVirtualXIDs(TransactionId limitXmin, bool allDbs)
+GetCurrentVirtualXIDs(TransactionId limitXmin, bool allDbs, int excludeVacuum)
 {
 	VirtualTransactionId *vxids;
 	ProcArrayStruct *arrayP = procArray;
@@ -1029,6 +1031,9 @@ GetCurrentVirtualXIDs(TransactionId limitXmin, bool allDbs)
 		if (proc == MyProc)
 			continue;
 
+		if (excludeVacuum & proc->vacuumFlags)
+			continue;
+
 		if (allDbs || proc->databaseId == MyDatabaseId)
 		{
 			/* Fetch xmin just once - might change on us? */
diff --git a/src/include/storage/procarray.h b/src/include/storage/procarray.h
index 405e046fa8..567ea64654 100644
--- a/src/include/storage/procarray.h
+++ b/src/include/storage/procarray.h
@@ -37,7 +37,7 @@ extern int	BackendXidGetPid(TransactionId xid);
 extern bool IsBackendPid(int pid);
 
 extern VirtualTransactionId *GetCurrentVirtualXIDs(TransactionId limitXmin,
-					  bool allDbs);
+					  bool allDbs, int excludeVacuum);
 extern int	CountActiveBackends(void);
 extern int	CountDBBackends(Oid databaseid);
 extern int	CountUserBackends(Oid roleid);