postgrespro
diff --git a/‎doc/src/sgml/release-9.5.sgml
Lines changed: 1 addition & 1 deletion b/‎doc/src/sgml/release-9.5.sgml
Lines changed: 1 addition & 1 deletion
diff --git a/‎src/backend/commands/vacuum.c
Lines changed: 19 additions & 11 deletions b/‎src/backend/commands/vacuum.c
Lines changed: 19 additions & 11 deletions
diff --git a/‎src/backend/postmaster/pgstat.c
Lines changed: 10 additions & 1 deletion b/‎src/backend/postmaster/pgstat.c
Lines changed: 10 additions & 1 deletion
@@ -2271,7 +2271,7 @@ Add GUC and storage parameter to set the maximum size of GIN pending list.
 -->
        <para>
         Add per-table autovacuum logging control via new
-        <varname>log_min_autovacuum_duration</> storage parameter
+        <varname>log_autovacuum_min_duration</> storage parameter
         (Michael Paquier)
        </para>
       </listitem>
 
@@ -1050,7 +1050,7 @@ vac_truncate_clog(TransactionId frozenXID,
 				  TransactionId lastSaneFrozenXid,
 				  MultiXactId lastSaneMinMulti)
 {
-	TransactionId myXID = GetCurrentTransactionId();
+	TransactionId nextXID = ReadNewTransactionId();
 	Relation	relation;
 	HeapScanDesc scan;
 	HeapTuple	tuple;
@@ -1066,6 +1066,12 @@ vac_truncate_clog(TransactionId frozenXID,
 	/*
 	 * Scan pg_database to compute the minimum datfrozenxid/datminmxid
 	 *
+	 * Since vac_update_datfrozenxid updates datfrozenxid/datminmxid in-place,
+	 * the values could change while we look at them.  Fetch each one just
+	 * once to ensure sane behavior of the comparison logic.  (Here, as in
+	 * many other places, we assume that fetching or updating an XID in shared
+	 * storage is atomic.)
+	 *
 	 * Note: we need not worry about a race condition with new entries being
 	 * inserted by CREATE DATABASE.  Any such entry will have a copy of some
 	 * existing DB's datfrozenxid, and that source DB cannot be ours because
@@ -1081,10 +1087,12 @@ vac_truncate_clog(TransactionId frozenXID,
 
 	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
 	{
-		Form_pg_database dbform = (Form_pg_database) GETSTRUCT(tuple);
+		volatile FormData_pg_database *dbform = (Form_pg_database) GETSTRUCT(tuple);
+		TransactionId datfrozenxid = dbform->datfrozenxid;
+		TransactionId datminmxid = dbform->datminmxid;
 
-		Assert(TransactionIdIsNormal(dbform->datfrozenxid));
-		Assert(MultiXactIdIsValid(dbform->datminmxid));
+		Assert(TransactionIdIsNormal(datfrozenxid));
+		Assert(MultiXactIdIsValid(datminmxid));
 
 		/*
 		 * If things are working properly, no database should have a
@@ -1095,21 +1103,21 @@ vac_truncate_clog(TransactionId frozenXID,
 		 * databases have been scanned and cleaned up.  (We will issue the
 		 * "already wrapped" warning if appropriate, though.)
 		 */
-		if (TransactionIdPrecedes(lastSaneFrozenXid, dbform->datfrozenxid) ||
-			MultiXactIdPrecedes(lastSaneMinMulti, dbform->datminmxid))
+		if (TransactionIdPrecedes(lastSaneFrozenXid, datfrozenxid) ||
+			MultiXactIdPrecedes(lastSaneMinMulti, datminmxid))
 			bogus = true;
 
-		if (TransactionIdPrecedes(myXID, dbform->datfrozenxid))
+		if (TransactionIdPrecedes(nextXID, datfrozenxid))
 			frozenAlreadyWrapped = true;
-		else if (TransactionIdPrecedes(dbform->datfrozenxid, frozenXID))
+		else if (TransactionIdPrecedes(datfrozenxid, frozenXID))
 		{
-			frozenXID = dbform->datfrozenxid;
+			frozenXID = datfrozenxid;
 			oldestxid_datoid = HeapTupleGetOid(tuple);
 		}
 
-		if (MultiXactIdPrecedes(dbform->datminmxid, minMulti))
+		if (MultiXactIdPrecedes(datminmxid, minMulti))
 		{
-			minMulti = dbform->datminmxid;
+			minMulti = datminmxid;
 			minmulti_datoid = HeapTupleGetOid(tuple);
 		}
 	}
 
@@ -5351,7 +5351,16 @@ pgstat_db_requested(Oid databaseid)
 {
 	slist_iter	iter;
 
-	/* Check the databases if they need to refresh the stats. */
+	/*
+	 * If any requests are outstanding at all, we should write the stats for
+	 * shared catalogs (the "database" with OID 0).  This ensures that
+	 * backends will see up-to-date stats for shared catalogs, even though
+	 * they send inquiry messages mentioning only their own DB.
+	 */
+	if (databaseid == InvalidOid && !slist_is_empty(&last_statrequests))
+		return true;
+
+	/* Search to see if there's an open request to write this database. */
 	slist_foreach(iter, &last_statrequests)
 	{
 		DBWriteRequest *req = slist_container(DBWriteRequest, next, iter.cur);