Fix some bugs in part_removed(

Author: knizhnik

shard.sql

@@ -264,9 +264,12 @@ BEGIN
 	RAISE DEBUG '[SHMN] part_removed trigger called for part %, owner %',
 		OLD.part_name, OLD.owner;
 
+	ASSERT (OLD.prv IS NULL OR OLD.nxt IS NULL), 'We currently do not support redundancy level > 2';
+
 	IF OLD.prv IS NOT NULL THEN
 		prev_src_lname := shardman.get_data_lname(OLD.part_name, OLD.prv, OLD.owner);
 	ELSE
+	    -- Primaty is moved
 	    select * from shardman.partitions where owner=OLD.nxt and part_name=OLD.part_name into new_primary;
 	END IF;
 	IF OLD.nxt IS NOT NULL THEN
@@ -292,30 +295,30 @@ BEGIN
 			PERFORM shardman.remove_sync_standby(src_next_lname);
 		END IF;
 		-- Drop old table anyway
-		-- ???? Can we really do it now? We will have FDW pointing to removed table... 
 		EXECUTE format('DROP TABLE IF EXISTS %I', OLD.part_name);
 	ELSEIF me = OLD.prv THEN -- node with prev replica
 		-- Wait sometime to let other node first remove subscription
 		PERFORM pg_sleep(drop_slot_delay);
 		-- Drop pub for old channel prev -> src
 		PERFORM shardman.drop_repslot_and_pub(prev_src_lname);
 		PERFORM shardman.remove_sync_standby(prev_src_lname);
+		-- Update L2-list (TODO: change replication model from chain to star)
 		PERFORM update shardman.partitions set nxt=OLD.nxt where owner=me and part_name=OLD.part_name;
 	ELSEIF me = OLD.nxt THEN -- node with next replica
 		-- Drop sub for old channel src -> next
 		PERFORM shardman.eliminate_sub(src_next_lname);
+		-- Update L2-list (TODO: change replication model from chain to star)
 		PERFORM update shardman.partitions set prv=OLD.prv where owner=me and part_name=OLD.part_name;
-		-- This replica is promoted to primary node, so drop trigger disabling writes to the table
+	    -- This replica is promoted to primary node, so drop trigger disabling writes to the table
 		PERFORM readonly_replica_off(part_name);
-		-- and replace FDW with local partition
-	    PERFORM shardman.replace_usual_part_with_foreign(new_primary);
+		-- Replace FDW with local partition
+	    PERFORM shardman.replace_foreign_part_with_usual(new_primary);
  	END IF;
 
 	-- If primary was moved 
 	IF OLD.prv IS NULL THEN
-	   -- And update fdw almost everywhere
+	   -- then update fdw almost everywhere
 	   PERFORM shardman.update_fdw_server(new_primary);
-	   PERFORM shardman.replace_foreign_part_with_usual(NEW);
 	END IF;
 
 	RETURN NULL;