/*
 * Function to manage pre-creation of the next partitions in a time-based partition set.
 * Also manages dropping old partitions if the retention option is set.
 */
CREATE FUNCTION run_maintenance() RETURNS void 
    LANGUAGE plpgsql SECURITY DEFINER
    AS $$
DECLARE

v_adv_lock                      boolean;
v_create_count                  int := 0;
v_current_partition_timestamp   timestamp;
v_datetime_string               text;
v_drop_count                    int := 0;
v_job_id                        bigint;
v_jobmon_schema                 text;
v_last_partition_timestamp      timestamp;
v_old_search_path               text;
v_premade_count                 int;
v_quarter                       text;
v_step_id                       bigint;
v_row                           record;
v_time_position                 int;
v_year                          text;

BEGIN

v_adv_lock := pg_try_advisory_lock(hashtext('pg_partman run_maintenance'));
IF v_adv_lock = 'false' THEN
    RAISE NOTICE 'Partman maintenance already running.';
    RETURN;
END IF;

SELECT nspname INTO v_jobmon_schema FROM pg_namespace n, pg_extension e WHERE e.extname = 'pg_jobmon' AND e.extnamespace = n.oid;
IF v_jobmon_schema IS NOT NULL THEN
    SELECT current_setting('search_path') INTO v_old_search_path;
    EXECUTE 'SELECT set_config(''search_path'',''@extschema@,'||v_jobmon_schema||''',''false'')';
END IF;

IF v_jobmon_schema IS NOT NULL THEN
    v_job_id := add_job('PARTMAN RUN MAINTENANCE');
    v_step_id := add_step(v_job_id, 'Running maintenance loop');
END IF;

FOR v_row IN 
SELECT parent_table
    , type
    , part_interval::interval
    , control
    , premake
    , datetime_string
    , last_partition
    , undo_in_progress
FROM @extschema@.part_config WHERE type = 'time-static' OR type = 'time-dynamic'
LOOP

    CONTINUE WHEN v_row.undo_in_progress;
    
    CASE
        WHEN v_row.part_interval = '15 mins' THEN
            v_current_partition_timestamp := date_trunc('hour', CURRENT_TIMESTAMP) + 
                '15min'::interval * floor(date_part('minute', CURRENT_TIMESTAMP) / 15.0);
        WHEN v_row.part_interval = '30 mins' THEN
            v_current_partition_timestamp := date_trunc('hour', CURRENT_TIMESTAMP) + 
                '30min'::interval * floor(date_part('minute', CURRENT_TIMESTAMP) / 30.0);
        WHEN v_row.part_interval = '1 hour' THEN
            v_current_partition_timestamp := date_trunc('hour', CURRENT_TIMESTAMP);
         WHEN v_row.part_interval = '1 day' THEN
            v_current_partition_timestamp := date_trunc('day', CURRENT_TIMESTAMP);
        WHEN v_row.part_interval = '1 week' THEN
            v_current_partition_timestamp := date_trunc('week', CURRENT_TIMESTAMP);
        WHEN v_row.part_interval = '1 month' THEN
            v_current_partition_timestamp := date_trunc('month', CURRENT_TIMESTAMP);
        WHEN v_row.part_interval = '3 months' THEN
            v_current_partition_timestamp := date_trunc('quarter', CURRENT_TIMESTAMP);
        WHEN v_row.part_interval = '1 year' THEN
            v_current_partition_timestamp := date_trunc('year', CURRENT_TIMESTAMP);
    END CASE;

    -- Get position of last occurance of '_p' in child partition name
    v_time_position := (length(v_row.last_partition) - position('p_' in reverse(v_row.last_partition))) + 2;
    IF v_row.part_interval != '3 months' THEN
       v_last_partition_timestamp := to_timestamp(substring(v_row.last_partition from v_time_position), v_row.datetime_string);
    ELSE
        -- to_timestamp doesn't recognize 'Q' date string formater. Handle it
        v_year := split_part(substring(v_row.last_partition from v_time_position), 'q', 1);
        v_quarter := split_part(substring(v_row.last_partition from v_time_position), 'q', 2);
        CASE
            WHEN v_quarter = '1' THEN
                v_last_partition_timestamp := to_timestamp(v_year || '-01-01', 'YYYY-MM-DD');
            WHEN v_quarter = '2' THEN
                v_last_partition_timestamp := to_timestamp(v_year || '-04-01', 'YYYY-MM-DD');
            WHEN v_quarter = '3' THEN
                v_last_partition_timestamp := to_timestamp(v_year || '-07-01', 'YYYY-MM-DD');
            WHEN v_quarter = '4' THEN
                v_last_partition_timestamp := to_timestamp(v_year || '-10-01', 'YYYY-MM-DD');
        END CASE;
    END IF;

    -- Check and see how many premade partitions there are.
    v_premade_count = round(EXTRACT('epoch' FROM age(v_last_partition_timestamp, v_current_partition_timestamp)) / EXTRACT('epoch' FROM v_row.part_interval::interval));
    -- Loop premaking until config setting is met. Allows it to catch up if it fell behind or if premake changed.
    WHILE v_premade_count < v_row.premake LOOP
        EXECUTE 'SELECT @extschema@.create_next_time_partition('||quote_literal(v_row.parent_table)||')';
        v_create_count := v_create_count + 1;
        IF v_row.type = 'time-static' THEN
            EXECUTE 'SELECT @extschema@.create_time_function('||quote_literal(v_row.parent_table)||')';
        END IF;
        v_last_partition_timestamp := v_last_partition_timestamp + v_row.part_interval;
        v_premade_count = round(EXTRACT('epoch' FROM age(v_last_partition_timestamp, v_current_partition_timestamp)) / EXTRACT('epoch' FROM v_row.part_interval::interval));
    END LOOP;

END LOOP; -- end of creation loop

-- Manage dropping old partitions if retention option is set
FOR v_row IN 
    SELECT parent_table FROM @extschema@.part_config WHERE retention IS NOT NULL AND undo_in_progress = false AND (type = 'time-static' OR type = 'time-dynamic')
LOOP
    v_drop_count := v_drop_count + @extschema@.drop_partition_time(v_row.parent_table);   
END LOOP; 
FOR v_row IN 
    SELECT parent_table FROM @extschema@.part_config WHERE retention IS NOT NULL AND undo_in_progress = false AND (type = 'id-static' OR type = 'id-dynamic')
LOOP
    v_drop_count := v_drop_count + @extschema@.drop_partition_id(v_row.parent_table);
END LOOP; 

IF v_jobmon_schema IS NOT NULL THEN
    PERFORM update_step(v_step_id, 'OK', 'Partition maintenance finished. '||v_create_count||' partitons made. '||v_drop_count||' partitions dropped.');
    PERFORM close_job(v_job_id);
    EXECUTE 'SELECT set_config(''search_path'','''||v_old_search_path||''',''false'')';
END IF;

PERFORM pg_advisory_unlock(hashtext('pg_partman run_maintenance'));

EXCEPTION
    WHEN QUERY_CANCELED THEN
        PERFORM pg_advisory_unlock(hashtext('pg_partman run_maintenance'));
        RAISE EXCEPTION '%', SQLERRM;
    WHEN OTHERS THEN
        IF v_jobmon_schema IS NOT NULL THEN
            EXECUTE 'SELECT set_config(''search_path'',''@extschema@,'||v_jobmon_schema||''',''false'')';
            IF v_job_id IS NULL THEN
                v_job_id := add_job('PARTMAN RUN MAINTENANCE');
                v_step_id := add_step(v_job_id, 'EXCEPTION before job logging started');
            END IF;
            IF v_step_id IS NULL THEN
                v_step_id := add_step(v_job_id, 'EXCEPTION before first step logged');
            END IF;
            PERFORM update_step(v_step_id, 'CRITICAL', 'ERROR: '||coalesce(SQLERRM,'unknown'));
            PERFORM fail_job(v_job_id);
            EXECUTE 'SELECT set_config(''search_path'','''||v_old_search_path||''',''false'')';
        END IF;
        PERFORM pg_advisory_unlock(hashtext('pg_partman run_maintenance'));
        RAISE EXCEPTION '%', SQLERRM;
END
$$;
