6.76. logswitch_start()

Function Properties

Language: PLPGSQL

Return Type: integer

logswitch_start() Initiate a log table switch if none is in progress

DECLARE
	v_current_status	int4;
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 = 0: sl_log_1 active, sl_log_2 clean
	-- Initiate a switch to sl_log_2.
	-- ----
	if v_current_status = 0 then
		perform "pg_catalog".setval('sl_log_status', 3);
		perform registry_set_timestamp(
				'logswitch.laststart', now()::timestamp);
		raise notice 'Slony-I: Logswitch to sl_log_2 initiated';
		return 2;
	end if;

	-- ----
	-- status = 1: sl_log_2 active, sl_log_1 clean
	-- Initiate a switch to sl_log_1.
	-- ----
	if v_current_status = 1 then
		perform "pg_catalog".setval('sl_log_status', 2);
		perform registry_set_timestamp(
				'logswitch.laststart', now()::timestamp);
		raise notice 'Slony-I: Logswitch to sl_log_1 initiated';
		return 1;
	end if;

	raise exception 'Previous logswitch still in progress';
END;