Teach autovacuum how to determine whether a temp table belongs to a crashed

backend.  If so, send a LOG message to the postmaster log, and if the table
is beyond the vacuum-for-wraparound horizon, forcibly drop it.  Per recent
discussions.  Perhaps we ought to back-patch this, but it probably needs
to age a bit in HEAD first.

src/backend/catalog/namespace.c

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/namespace.c,v 1.106 2008/06/19 00:46:04 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/namespace.c,v 1.107 2008/07/01 02:09:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2209,6 +2209,32 @@ isOtherTempNamespace(Oid namespaceId)
 	return isAnyTempNamespace(namespaceId);
 }
 
+/*
+ * GetTempNamespaceBackendId - if the given namespace is a temporary-table
+ * namespace (either my own, or another backend's), return the BackendId
+ * that owns it.  Temporary-toast-table namespaces are included, too.
+ * If it isn't a temp namespace, return -1.
+ */
+int
+GetTempNamespaceBackendId(Oid namespaceId)
+{
+	int			result;
+	char	   *nspname;
+
+	/* See if the namespace name starts with "pg_temp_" or "pg_toast_temp_" */
+	nspname = get_namespace_name(namespaceId);
+	if (!nspname)
+		return -1;				/* no such namespace? */
+	if (strncmp(nspname, "pg_temp_", 8) == 0)
+		result = atoi(nspname + 8);
+	else if (strncmp(nspname, "pg_toast_temp_", 14) == 0)
+		result = atoi(nspname + 14);
+	else
+		result = -1;
+	pfree(nspname);
+	return result;
+}
+
 /*
  * GetTempToastNamespace - get the OID of my temporary-toast-table namespace,
  * which must already be assigned.	(This is only used when creating a toast

src/backend/postmaster/autovacuum.c

@@ -55,7 +55,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.79 2008/06/05 15:47:32 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/autovacuum.c,v 1.80 2008/07/01 02:09:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -71,6 +71,7 @@
 #include "access/heapam.h"
 #include "access/transam.h"
 #include "access/xact.h"
+#include "catalog/dependency.h"
 #include "catalog/indexing.h"
 #include "catalog/namespace.h"
 #include "catalog/pg_autovacuum.h"
@@ -90,7 +91,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "storage/procarray.h"
-#include "storage/sinval.h"
+#include "storage/sinvaladt.h"
 #include "tcop/tcopprot.h"
 #include "utils/flatfiles.h"
 #include "utils/fmgroids.h"
@@ -275,10 +276,6 @@ static void autovac_balance_cost(void);
 static void do_autovacuum(void);
 static void FreeWorkerInfo(int code, Datum arg);
 
-static void relation_check_autovac(Oid relid, Form_pg_class classForm,
-					Form_pg_autovacuum avForm, PgStat_StatTabEntry *tabentry,
-					   List **table_oids, List **table_toast_list,
-					   List **toast_oids);
 static autovac_table *table_recheck_autovac(Oid relid);
 static void relation_needs_vacanalyze(Oid relid, Form_pg_autovacuum avForm,
 						  Form_pg_class classForm,
@@ -1912,19 +1909,16 @@ do_autovacuum(void)
 		PgStat_StatTabEntry *tabentry;
 		HeapTuple	avTup;
 		Oid			relid;
+		bool		dovacuum;
+		bool		doanalyze;
+		bool		wraparound;
+		int			backendID;
 
 		/* Consider only regular and toast tables. */
 		if (classForm->relkind != RELKIND_RELATION &&
 			classForm->relkind != RELKIND_TOASTVALUE)
 			continue;
 
-		/*
-		 * Skip temp tables (i.e. those in temp namespaces).  We cannot safely
-		 * process other backends' temp tables.
-		 */
-		if (isAnyTempNamespace(classForm->relnamespace))
-			continue;
-
 		relid = HeapTupleGetOid(tuple);
 
 		/* Fetch the pg_autovacuum tuple for the relation, if any */
@@ -1936,8 +1930,76 @@ do_autovacuum(void)
 		tabentry = get_pgstat_tabentry_relid(relid, classForm->relisshared,
 											 shared, dbentry);
 
-		relation_check_autovac(relid, classForm, avForm, tabentry,
+		/* Check if it needs vacuum or analyze */
-							   &table_oids, &table_toast_list, &toast_oids);
+		relation_needs_vacanalyze(relid, avForm, classForm, tabentry,
+								  &dovacuum, &doanalyze, &wraparound);
+
+		/*
+		 * Check if it is a temp table (presumably, of some other backend's).
+		 * We cannot safely process other backends' temp tables.
+		 */
+		backendID = GetTempNamespaceBackendId(classForm->relnamespace);
+
+		if (backendID > 0)
+		{
+			/* We just ignore it if the owning backend is still active */
+			if (backendID == MyBackendId || !BackendIdIsActive(backendID))
+			{
+				/*
+				 * We found an orphan temp table (which was probably left
+				 * behind by a crashed backend).  If it's so old as to need
+				 * vacuum for wraparound, forcibly drop it.  Otherwise just
+				 * log a complaint.
+				 */
+				if (wraparound && classForm->relkind == RELKIND_RELATION)
+				{
+					ObjectAddress object;
+
+					ereport(LOG,
+							(errmsg("autovacuum: dropping orphan temp table \"%s\".\"%s\" in database \"%s\"",
+									get_namespace_name(classForm->relnamespace),
+									NameStr(classForm->relname),
+									get_database_name(MyDatabaseId))));
+					object.classId = RelationRelationId;
+					object.objectId = relid;
+					object.objectSubId = 0;
+					performDeletion(&object, DROP_CASCADE);
+				}
+				else
+				{
+					ereport(LOG,
+							(errmsg("autovacuum: found orphan temp table \"%s\".\"%s\" in database \"%s\"",
+									get_namespace_name(classForm->relnamespace),
+									NameStr(classForm->relname),
+									get_database_name(MyDatabaseId))));
+				}
+			}
+		}
+		else if (classForm->relkind == RELKIND_RELATION)
+		{
+			/* Plain relations that need work are added to table_oids */
+			if (dovacuum || doanalyze)
+				table_oids = lappend_oid(table_oids, relid);
+			else if (OidIsValid(classForm->reltoastrelid))
+			{
+				/*
+				 * If it doesn't appear to need vacuuming, but it has a toast
+				 * table, remember the association to revisit below.
+				 */
+				av_relation *rel = palloc(sizeof(av_relation));
+
+				rel->ar_relid = relid;
+				rel->ar_toastrelid = classForm->reltoastrelid;
+
+				table_toast_list = lappend(table_toast_list, rel);
+			}
+		}
+		else
+		{
+			/* TOAST relations that need vacuum are added to toast_oids */
+			if (dovacuum)
+				toast_oids = lappend_oid(toast_oids, relid);
+		}
 
 		if (HeapTupleIsValid(avTup))
 			heap_freetuple(avTup);
@@ -2231,56 +2293,6 @@ get_pgstat_tabentry_relid(Oid relid, bool isshared, PgStat_StatDBEntry *shared,
 	return tabentry;
 }
 
-/*
- * relation_check_autovac
- *
- * For a given relation (either a plain table or TOAST table), check whether it
- * needs vacuum or analyze.
- *
- * Plain tables that need either are added to the table_list.  TOAST tables
- * that need vacuum are added to toast_list.  Plain tables that don't need
- * either but which have a TOAST table are added, as a struct, to
- * table_toast_list.  The latter is to allow appending the OIDs of the plain
- * tables whose TOAST table needs vacuuming into the plain tables list, which
- * allows us to substantially reduce the number of "rechecks" that we need to
- * do later on.
- */
-static void
-relation_check_autovac(Oid relid, Form_pg_class classForm,
-					Form_pg_autovacuum avForm, PgStat_StatTabEntry *tabentry,
-					   List **table_oids, List **table_toast_list,
-					   List **toast_oids)
-{
-	bool		dovacuum;
-	bool		doanalyze;
-	bool		dummy;
-
-	relation_needs_vacanalyze(relid, avForm, classForm, tabentry,
-							  &dovacuum, &doanalyze, &dummy);
-
-	if (classForm->relkind == RELKIND_TOASTVALUE)
-	{
-		if (dovacuum)
-			*toast_oids = lappend_oid(*toast_oids, relid);
-	}
-	else
-	{
-		Assert(classForm->relkind == RELKIND_RELATION);
-
-		if (dovacuum || doanalyze)
-			*table_oids = lappend_oid(*table_oids, relid);
-		else if (OidIsValid(classForm->reltoastrelid))
-		{
-			av_relation *rel = palloc(sizeof(av_relation));
-
-			rel->ar_relid = relid;
-			rel->ar_toastrelid = classForm->reltoastrelid;
-
-			*table_toast_list = lappend(*table_toast_list, rel);
-		}
-	}
-}
-
 /*
  * table_recheck_autovac
  *

src/backend/storage/ipc/sinvaladt.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.72 2008/06/20 00:24:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/sinvaladt.c,v 1.73 2008/07/01 02:09:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -357,6 +357,33 @@ CleanupInvalidationState(int status, Datum arg)
 	LWLockRelease(SInvalWriteLock);
 }
 
+/*
+ * BackendIdIsActive
+ *		Test if the given backend ID is currently assigned to a process.
+ */
+bool
+BackendIdIsActive(int backendID)
+{
+	bool		result;
+	SISeg	   *segP = shmInvalBuffer;
+
+	/* Need to lock out additions/removals of backends */
+	LWLockAcquire(SInvalWriteLock, LW_SHARED);
+
+	if (backendID > 0 && backendID <= segP->lastBackend)
+	{
+		ProcState  *stateP = &segP->procState[backendID - 1];
+
+		result = (stateP->procPid != 0);
+	}
+	else
+		result = false;
+
+	LWLockRelease(SInvalWriteLock);
+
+	return result;
+}
+
 /*
  * SIInsertDataEntries
  *		Add new invalidation message(s) to the buffer.

src/include/catalog/namespace.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/catalog/namespace.h,v 1.53 2008/01/01 19:45:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/namespace.h,v 1.54 2008/07/01 02:09:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -95,6 +95,7 @@ extern bool isTempToastNamespace(Oid namespaceId);
 extern bool isTempOrToastNamespace(Oid namespaceId);
 extern bool isAnyTempNamespace(Oid namespaceId);
 extern bool isOtherTempNamespace(Oid namespaceId);
+extern int	GetTempNamespaceBackendId(Oid namespaceId);
 extern Oid	GetTempToastNamespace(void);
 extern void ResetTempTableNamespace(void);
 

src/include/storage/sinvaladt.h

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/sinvaladt.h,v 1.48 2008/06/19 21:32:56 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/storage/sinvaladt.h,v 1.49 2008/07/01 02:09:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -30,6 +30,7 @@
 extern Size SInvalShmemSize(void);
 extern void CreateSharedInvalidationState(void);
 extern void SharedInvalBackendInit(void);
+extern bool BackendIdIsActive(int backendID);
 
 extern void SIInsertDataEntries(const SharedInvalidationMessage *data, int n);
 extern int SIGetDataEntries(SharedInvalidationMessage *data, int datasize);