1.75. logswitch_finish( )

Function Properties

Language: PLPGSQL

Return Type: integer

logswitch_finish() Attempt to finalize a log table switch in progress

DECLARE
	v_current_status	int4;
	v_dummy				record;
BEGIN
	-- ----
	-- Grab the central configuration lock to prevent race conditions
	-- while changing the sl_log_status sequence value.
	-- ----
	lock table sl_config_lock;

	-- ----
	-- Get the current log status.
	-- ----
	select last_value into v_current_status from sl_log_status;

	-- ----
	-- status value 0 or 1 means that there is no log switch in progress
	-- ----
	if v_current_status = 0 or v_current_status = 1 then
		return 0;
	end if;

	-- ----
	-- status = 2: sl_log_1 active, cleanup sl_log_2
	-- ----
	if v_current_status = 2 then
		-- ----
		-- The cleanup thread calls us after it did the delete and
		-- vacuum of both log tables. If sl_log_2 is empty now, we
		-- can truncate it and the log switch is done.
		-- ----
		for v_dummy in select 1 from sl_log_2 loop
			-- ----
			-- Found a row ... log switch is still in progress.
			-- ----
			raise notice 'Slony-I: log switch to sl_log_1 still in progress - sl_log_2 not truncated';
			return -1;
		end loop;

		raise notice 'Slony-I: log switch to sl_log_1 complete - truncate sl_log_2';
		truncate sl_log_2;
		if exists (select * from "pg_catalog".pg_class c, "pg_catalog".pg_namespace n, "pg_catalog".pg_attribute a where c.relname = 'sl_log_2' and n.oid = c.relnamespace and a.attrelid = c.oid and a.attname = 'oid') then
	                execute 'alter table sl_log_2 set without oids;';
		end if;		
		perform "pg_catalog".setval('sl_log_status', 0);
		-- Run addPartialLogIndices() to try to add indices to unused sl_log_? table
		perform addPartialLogIndices();

		return 1;
	end if;

	-- ----
	-- status = 3: sl_log_2 active, cleanup sl_log_1
	-- ----
	if v_current_status = 3 then
		-- ----
		-- The cleanup thread calls us after it did the delete and
		-- vacuum of both log tables. If sl_log_2 is empty now, we
		-- can truncate it and the log switch is done.
		-- ----
		for v_dummy in select 1 from sl_log_1 loop
			-- ----
			-- Found a row ... log switch is still in progress.
			-- ----
			raise notice 'Slony-I: log switch to sl_log_2 still in progress - sl_log_1 not truncated';
			return -1;
		end loop;

		raise notice 'Slony-I: log switch to sl_log_2 complete - truncate sl_log_1';
		truncate sl_log_1;
		if exists (select * from "pg_catalog".pg_class c, "pg_catalog".pg_namespace n, "pg_catalog".pg_attribute a where c.relname = 'sl_log_1' and n.oid = c.relnamespace and a.attrelid = c.oid and a.attname = 'oid') then
	                execute 'alter table sl_log_1 set without oids;';
		end if;		
		perform "pg_catalog".setval('sl_log_status', 1);
		-- Run addPartialLogIndices() to try to add indices to unused sl_log_? table
		perform addPartialLogIndices();
		return 2;
	end if;
END;