CREATE FUNCTION @extschema@.drop_partition_id(
    p_parent_table text
    , p_retention bigint DEFAULT NULL
    , p_keep_table boolean DEFAULT NULL
    , p_keep_index boolean DEFAULT NULL
    , p_retention_schema text DEFAULT NULL
)
    RETURNS int
    LANGUAGE plpgsql
    SET search_path = @extschema@, pg_catalog, pg_temp
    AS $$
DECLARE

ex_context                          text;
ex_detail                           text;
ex_hint                             text;
ex_message                          text;
v_adv_lock                          boolean;
v_control                           text;
v_control_type                      text;
v_count                             int;
v_drop_count                        int := 0;
v_index                             record;
v_job_id                            bigint;
v_jobmon                            boolean;
v_jobmon_schema                     text;
v_max                               bigint;
v_new_search_path                   text;
v_old_search_path                   text;
v_parent_schema                     text;
v_parent_tablename                  text;
v_partition_interval                bigint;
v_partition_id                      bigint;
v_pubname_row                       record;
v_retention                         bigint;
v_retention_keep_index              boolean;
v_retention_keep_table              boolean;
v_retention_keep_publication        boolean;
v_retention_schema                  text;
v_row                               record;
v_row_max_id                        record;
v_sql                               text;
v_step_id                           bigint;
v_sub_parent                        text;

BEGIN
/*
 * Function to drop child tables from an id-based partition set.
 * Options to move table to different schema or actually drop the table from the database.
 */

v_adv_lock := pg_try_advisory_xact_lock(hashtext('pg_partman drop_partition_id'));
IF v_adv_lock = 'false' THEN
    RAISE NOTICE 'drop_partition_id already running.';
    RETURN 0;
END IF;

IF p_retention IS NULL THEN
    SELECT
        partition_interval::bigint
        , control
        , retention::bigint
        , retention_keep_table
        , retention_keep_index
        , retention_keep_publication
        , retention_schema
        , jobmon
    INTO
        v_partition_interval
        , v_control
        , v_retention
        , v_retention_keep_table
        , v_retention_keep_index
        , v_retention_keep_publication
        , v_retention_schema
        , v_jobmon
    FROM @extschema@.part_config
    WHERE parent_table = p_parent_table
    AND retention IS NOT NULL;

    IF v_partition_interval IS NULL THEN
        RAISE EXCEPTION 'Configuration for given parent table with a retention period not found: %', p_parent_table;
    END IF;
ELSE -- Allow override of configuration options
     SELECT
        partition_interval::bigint
        , control
        , retention_keep_table
        , retention_keep_index
        , retention_keep_publication
        , retention_schema
        , jobmon
    INTO
        v_partition_interval
        , v_control
        , v_retention_keep_table
        , v_retention_keep_index
        , v_retention_keep_publication
        , v_retention_schema
        , v_jobmon
    FROM @extschema@.part_config
    WHERE parent_table = p_parent_table;
    v_retention := p_retention;

    IF v_partition_interval IS NULL THEN
        RAISE EXCEPTION 'Configuration for given parent table not found: %', p_parent_table;
    END IF;
END IF;

SELECT general_type INTO v_control_type FROM @extschema@.check_control_type(v_parent_schema, v_parent_tablename, v_control);
IF v_control_type <> 'id' THEN
    RAISE EXCEPTION 'Data type of control column in given partition set is not an integer type';
END IF;

IF v_jobmon THEN
    SELECT nspname INTO v_jobmon_schema FROM pg_catalog.pg_namespace n, pg_catalog.pg_extension e WHERE e.extname = 'pg_jobmon'::name AND e.extnamespace = n.oid;
    IF v_jobmon_schema IS NOT NULL THEN
        SELECT current_setting('search_path') INTO v_old_search_path;
        IF v_jobmon_schema IS NOT NULL THEN
            v_new_search_path := format('%s,%s',v_jobmon_schema, v_old_search_path);
            EXECUTE format('SET LOCAL search_path TO %s', v_new_search_path);
        END IF;
    END IF;
END IF;

IF p_keep_table IS NOT NULL THEN
    v_retention_keep_table = p_keep_table;
END IF;
IF p_keep_index IS NOT NULL THEN
    v_retention_keep_index = p_keep_index;
END IF;
IF p_retention_schema IS NOT NULL THEN
    v_retention_schema = p_retention_schema;
END IF;

SELECT schemaname, tablename INTO v_parent_schema, v_parent_tablename
FROM pg_catalog.pg_tables
WHERE schemaname = split_part(p_parent_table, '.', 1)::name
AND tablename = split_part(p_parent_table, '.', 2)::name;

-- Loop through child tables starting from highest to get current max value in partition set
-- Avoids doing a scan on entire partition set and/or getting any values accidentally in default.
FOR v_row_max_id IN
    SELECT partition_schemaname, partition_tablename FROM @extschema@.show_partitions(p_parent_table, 'DESC')
LOOP
        EXECUTE format('SELECT trunc(max(%I)) FROM %I.%I', v_control, v_row_max_id.partition_schemaname, v_row_max_id.partition_tablename) INTO v_max;
        IF v_max IS NOT NULL THEN
            EXIT;
        END IF;
END LOOP;

SELECT sub_parent INTO v_sub_parent FROM @extschema@.part_config_sub WHERE sub_parent = p_parent_table;

-- Loop through child tables of the given parent
-- Must go in ascending order to avoid dropping what may be the "last" partition in the set after dropping tables that match retention period
FOR v_row IN
    SELECT partition_schemaname, partition_tablename FROM @extschema@.show_partitions(p_parent_table, 'ASC')
LOOP
     SELECT child_start_id INTO v_partition_id FROM @extschema@.show_partition_info(v_row.partition_schemaname||'.'||v_row.partition_tablename
        , v_partition_interval::text
        , p_parent_table);

    -- Add one interval to the start of the constraint period
    RAISE DEBUG 'drop_partition_id: v_retention: %, v_max: %, v_partition_id: %, v_partition_interval: %', v_retention, v_max, v_partition_id, v_partition_interval;
    IF v_retention <= (v_max - (v_partition_id + v_partition_interval)) THEN

        -- Do not allow final partition to be dropped if it is not a sub-partition parent
        SELECT count(*) INTO v_count FROM @extschema@.show_partitions(p_parent_table);
        IF v_count = 1 AND v_sub_parent IS NULL THEN
            RAISE WARNING 'Attempt to drop final partition in partition set % as part of retention policy. If you see this message multiple times for the same table, advise reviewing retention policy and/or data entry into the partition set. Also consider setting "infinite_time_partitions = true" if there are large gaps in data insertion.', p_parent_table;
            CONTINUE;
        END IF;

        -- Only create a jobmon entry if there's actual retention work done
        IF v_jobmon_schema IS NOT NULL AND v_job_id IS NULL THEN
            v_job_id := add_job(format('PARTMAN DROP ID PARTITION: %s', p_parent_table));
        END IF;

        IF v_jobmon_schema IS NOT NULL THEN
            v_step_id := add_step(v_job_id, format('Detach/Uninherit table %s.%s from %s', v_row.partition_schemaname, v_row.partition_tablename, p_parent_table));
        END IF;

        IF v_retention_keep_table = true OR v_retention_schema IS NOT NULL THEN
            -- No need to detach partition before dropping since it's going away anyway
            -- TODO Review this to see how to handle based on recent FK issues
            -- Avoids issue of FKs not allowing detachment (Github Issue #294).
            v_sql := format('ALTER TABLE %I.%I DETACH PARTITION %I.%I'
                , v_parent_schema
                , v_parent_tablename
                , v_row.partition_schemaname
                , v_row.partition_tablename);
            EXECUTE v_sql;

            IF v_retention_keep_index = false THEN
                FOR v_index IN
                     WITH child_info AS (
                        SELECT c1.oid
                        FROM pg_catalog.pg_class c1
                        JOIN pg_catalog.pg_namespace n1 ON c1.relnamespace = n1.oid
                        WHERE c1.relname = v_row.partition_tablename::name
                        AND n1.nspname = v_row.partition_schemaname::name
                    )
                    SELECT c.relname as name
                        , con.conname
                    FROM pg_catalog.pg_index i
                    JOIN pg_catalog.pg_class c ON i.indexrelid = c.oid
                    LEFT JOIN pg_catalog.pg_constraint con ON i.indexrelid = con.conindid
                    JOIN child_info ON i.indrelid = child_info.oid
                LOOP
                    IF v_jobmon_schema IS NOT NULL THEN
                        v_step_id := add_step(v_job_id, format('Drop index %s from %s.%s'
                            , v_index.name
                            , v_row.partition_schemaname
                            , v_row.partition_tablename));
                    END IF;
                    IF v_index.conname IS NOT NULL THEN
                        EXECUTE format('ALTER TABLE %I.%I DROP CONSTRAINT %I', v_row.partition_schemaname, v_row.partition_tablename, v_index.conname);
                    ELSE
                        EXECUTE format('DROP INDEX %I.%I', v_row.partition_schemaname, v_index.name);
                    END IF;
                    IF v_jobmon_schema IS NOT NULL THEN
                        PERFORM update_step(v_step_id, 'OK', 'Done');
                    END IF;
                END LOOP;
            END IF; -- end v_retention_keep_index IF

            -- Remove table from publication(s) if desired
            IF v_retention_keep_publication = false THEN
                FOR v_pubname_row IN
                    SELECT p.pubname
                    FROM pg_catalog.pg_publication_rel pr
                    JOIN pg_catalog.pg_publication p ON p.oid = pr.prpubid
                    JOIN pg_catalog.pg_class c ON c.oid = pr.prrelid
                    JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace
                    WHERE n.nspname = v_row.partition_schemaname
                    AND c.relname = v_row.partition_tablename
                LOOP
                    EXECUTE format('ALTER PUBLICATION %I DROP TABLE %I.%I', v_pubname_row.pubname, v_row.partition_schemaname, v_row.partition_tablename);
                END LOOP;
            END IF;

        END IF;

        IF v_retention_schema IS NULL THEN
            IF v_retention_keep_table = false THEN
                IF v_jobmon_schema IS NOT NULL THEN
                    v_step_id := add_step(v_job_id, format('Drop table %s.%s', v_row.partition_schemaname, v_row.partition_tablename));
                END IF;
                v_sql := 'DROP TABLE %I.%I';
                EXECUTE format(v_sql, v_row.partition_schemaname, v_row.partition_tablename);
                IF v_jobmon_schema IS NOT NULL THEN
                    PERFORM update_step(v_step_id, 'OK', 'Done');
                END IF;
            END IF;
        ELSE -- Move to new schema
            IF v_jobmon_schema IS NOT NULL THEN
                v_step_id := add_step(v_job_id, format('Moving table %s.%s to schema %s'
                                                        , v_row.partition_schemaname
                                                        , v_row.partition_tablename
                                                        , v_retention_schema));
            END IF;

            EXECUTE format('ALTER TABLE %I.%I SET SCHEMA %I'
                    , v_row.partition_schemaname
                    , v_row.partition_tablename
                    , v_retention_schema);

            IF v_jobmon_schema IS NOT NULL THEN
                PERFORM update_step(v_step_id, 'OK', 'Done');
            END IF;
        END IF; -- End retention schema if

        -- If child table is a subpartition, remove it from part_config & part_config_sub (should cascade due to FK)
        DELETE FROM @extschema@.part_config WHERE parent_table = v_row.partition_schemaname ||'.'||v_row.partition_tablename;

        v_drop_count := v_drop_count + 1;
    END IF; -- End retention check IF

END LOOP; -- End child table loop

IF v_jobmon_schema IS NOT NULL THEN
    IF v_job_id IS NOT NULL THEN
        v_step_id := add_step(v_job_id, 'Finished partition drop maintenance');
        PERFORM update_step(v_step_id, 'OK', format('%s partitions dropped.', v_drop_count));
        PERFORM close_job(v_job_id);
    END IF;
END IF;

RETURN v_drop_count;

EXCEPTION
    WHEN OTHERS THEN
        GET STACKED DIAGNOSTICS ex_message = MESSAGE_TEXT,
                                ex_context = PG_EXCEPTION_CONTEXT,
                                ex_detail = PG_EXCEPTION_DETAIL,
                                ex_hint = PG_EXCEPTION_HINT;
        IF v_jobmon_schema IS NOT NULL THEN
            IF v_job_id IS NULL THEN
                EXECUTE format('SELECT %I.add_job(''PARTMAN DROP ID PARTITION: %s'')', v_jobmon_schema, p_parent_table) INTO v_job_id;
                EXECUTE format('SELECT %I.add_step(%s, ''EXCEPTION before job logging started'')', v_jobmon_schema, v_job_id, p_parent_table) INTO v_step_id;
            ELSIF v_step_id IS NULL THEN
                EXECUTE format('SELECT %I.add_step(%s, ''EXCEPTION before first step logged'')', v_jobmon_schema, v_job_id) INTO v_step_id;
            END IF;
            EXECUTE format('SELECT %I.update_step(%s, ''CRITICAL'', %L)', v_jobmon_schema, v_step_id, 'ERROR: '||coalesce(SQLERRM,'unknown'));
            EXECUTE format('SELECT %I.fail_job(%s)', v_jobmon_schema, v_job_id);
        END IF;
        RAISE EXCEPTION '%
CONTEXT: %
DETAIL: %
HINT: %', ex_message, ex_context, ex_detail, ex_hint;
END
$$;
