Fix problem with process utulity statement context filter

Author: knizhnik

contrib/mmts/multimaster--1.0.sql

@@ -99,18 +99,23 @@ BEGIN
     FOR seq_class IN
         SELECT * FROM pg_class WHERE pg_class.relkind = 'S'
     LOOP
-        EXECUTE 'select * from ' || seq_class.relname || ';' INTO seq_tuple;
-        IF seq_tuple.increment_by != max_nodes THEN
-            altered := true;
-            RAISE NOTICE 'Altering step for sequence % to %.', seq_tuple.sequence_name, max_nodes;
-            EXECUTE 'ALTER SEQUENCE ' || seq_class.relname || ' INCREMENT BY ' || max_nodes || ';';
-        END IF;
-        IF (seq_tuple.last_value % max_nodes) != node_id THEN
-            altered := true;
-            new_start := (seq_tuple.last_value / max_nodes + 1)*max_nodes + node_id;
-            RAISE NOTICE 'Altering start for sequence % to %.', seq_tuple.sequence_name, new_start;
-            EXECUTE 'ALTER SEQUENCE ' || seq_class.relname || ' RESTART WITH ' || new_start || ';';
-        END IF;
+	    BEGIN
+            EXECUTE 'select * from ' || seq_class.relname || ';' INTO seq_tuple;
+            IF seq_tuple.increment_by != max_nodes THEN
+                altered := true;
+                RAISE NOTICE 'Altering step for sequence % to %.', seq_tuple.sequence_name, max_nodes;
+                EXECUTE 'ALTER SEQUENCE ' || seq_class.relname || ' INCREMENT BY ' || max_nodes || ';';
+            END IF;
+            IF (seq_tuple.last_value % max_nodes) != node_id THEN
+                altered := true;
+                new_start := (seq_tuple.last_value / max_nodes + 1)*max_nodes + node_id;
+                RAISE NOTICE 'Altering start for sequence % to %.', seq_tuple.sequence_name, new_start;
+                EXECUTE 'ALTER SEQUENCE ' || seq_class.relname || ' RESTART WITH ' || new_start || ';';
+            END IF;
+       EXCEPTION
+            WHEN OTHERS THEN
+	            RAISE NOTICE 'Failed to alter sequence %s', seq_class.relname;
+       END;
     END LOOP;
     IF altered = false THEN
         RAISE NOTICE 'All found sequnces have proper params.';

contrib/mmts/multimaster.c

@@ -46,6 +46,7 @@
 #include "utils/builtins.h"
 #include "utils/memutils.h"
 #include "commands/dbcommands.h"
+#include "commands/extension.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -4865,7 +4866,8 @@ static void MtmProcessUtility(Node *parsetree, const char *queryString,
 	bool skipCommand = false;
 	bool executed = false;
 
-	MTM_LOG3("%d: Process utility statement %s", MyProcPid, queryString);
+	MTM_LOG3("%d: Process utility statement tag=%d, context=%d, issubtrans=%d, query=%s", 
+			 MyProcPid, nodeTag(parsetree), context, IsSubTransaction(), queryString);
 	switch (nodeTag(parsetree))
 	{
 		case T_TransactionStmt:
@@ -5119,7 +5121,13 @@ static void MtmProcessUtility(Node *parsetree, const char *queryString,
 	}
 
 	/* XXX: dirty. Clear on new tx */
-	if (!skipCommand && (context != PROCESS_UTILITY_SUBCOMMAND || MtmUtilityProcessedInXid != GetCurrentTransactionId()))
+	/* Some "black magic here":( We want to avoid redundant execution of utility statement by ProcessUtilitySlow (which is done with PROCESS_UTILITY_SUBCOMMAND).
+	 * But if we allow only PROCESS_UTILITY_TOPLEVEL context, then we will not replicated DDL inside dynamic queries in plpgsql functions (see https://jira.postgrespro.ru/browse/CORE-526).
+	 * If we disable only PROCESS_UTILITY_SUBCOMMAND, then we will get problems with "create extension" which is executed also in PROCESS_UTILITY_QUERY context.
+	 * So workaround at this moment is to treat extension as special case. 
+	 * TODO: try to find right solution and rewrite this dummy check.
+	 */
+	if (!skipCommand && (context == PROCESS_UTILITY_TOPLEVEL || (context == PROCESS_UTILITY_QUERY && !creating_extension) || MtmUtilityProcessedInXid != GetCurrentTransactionId()))
 		MtmUtilityProcessedInXid = InvalidTransactionId;
 
 	if (!skipCommand && !MtmTx.isReplicated && (MtmUtilityProcessedInXid == InvalidTransactionId)) {