timescaledb/extension/sql/main/ddl_triggers.sql

/*
  This file creates function to intercept ddl commands executed on the
  main tables of hypertables and convert them to commands that alter
  the coresponding schema structure of hypertables.

  The basic idea is that the main table is a regular sql tables that represents
  the hypertable. DDL changes to that table have corresponding changes on the hypertable.

  The intercepted schema changes work as follows:
    1) a ddl command is intercepted and it is determined whether it's on a hypertable, if not exit.
    2) it is determined whether this is a user or trigger initate command. If it is trigger initiated, exit.
    3) send the corresponding hypertable ddl command to the meta node.

  Because ddl commands cannot be "canceled" without an error, all comands are allowed to succeed. This is
  why the command sent to the meta node always contains a parameter for the node the ddl command was executed on
  (so that the meta node can know that the main table on that node was already modified and does not needed to be
    modified again).

*/

--Handles ddl create index commands on hypertables
CREATE OR REPLACE FUNCTION _iobeamdb_internal.ddl_process_create_index()
  RETURNS event_trigger
 LANGUAGE plpgsql
  AS
$BODY$
DECLARE
  info           record;
  table_oid      regclass;
  def            TEXT;
  hypertable_row _iobeamdb_catalog.hypertable;
BEGIN
  FOR info IN SELECT * FROM pg_event_trigger_ddl_commands()
    LOOP
    --get table oid
    SELECT indrelid INTO STRICT table_oid
    FROM pg_catalog.pg_index
    WHERE indexrelid = info.objid;

    IF NOT _iobeamdb_internal.is_main_table(table_oid) OR current_setting('io.ignore_ddl_in_trigger', true) = 'true' THEN
      RETURN;
    END IF;

    def = _iobeamdb_internal.get_general_index_definition(info.objid, table_oid);

    hypertable_row := _iobeamdb_internal.hypertable_from_main_table(table_oid);

    PERFORM _iobeamdb_meta_api.add_index(
            hypertable_row.name,
            hypertable_row.main_schema_name,
            (SELECT relname FROM pg_class WHERE oid = info.objid::regclass),
            def
        );
  END LOOP;
END
$BODY$;

--Handles ddl alter index commands on hypertables
CREATE OR REPLACE FUNCTION _iobeamdb_internal.ddl_process_alter_index()
  RETURNS event_trigger
 LANGUAGE plpgsql
  AS
$BODY$
DECLARE
  info record;
  table_oid regclass;
BEGIN
  FOR info IN SELECT * FROM pg_event_trigger_ddl_commands()
    LOOP
      SELECT indrelid INTO STRICT table_oid
      FROM pg_catalog.pg_index
      WHERE indexrelid = info.objid;

      IF NOT _iobeamdb_internal.is_main_table(table_oid) THEN
        RETURN;
      END IF;

      RAISE EXCEPTION 'ALTER INDEX not supported on hypertable %', table_oid
      USING ERRCODE = 'IO101';
  END LOOP;
END
$BODY$;


--Handles ddl drop index commands on hypertables
CREATE OR REPLACE FUNCTION _iobeamdb_internal.ddl_process_drop_index()
  RETURNS event_trigger
 LANGUAGE plpgsql
  AS
$BODY$
DECLARE
  info           record;
  table_oid      regclass;
  hypertable_row _iobeamdb_catalog.hypertable;
BEGIN
  FOR info IN SELECT * FROM  pg_event_trigger_dropped_objects()
    LOOP
      SELECT  format('%I.%I', h.main_schema_name, h.main_table_name) INTO table_oid
      FROM _iobeamdb_catalog.hypertable h
      INNER JOIN _iobeamdb_catalog.hypertable_index i ON (i.hypertable_name = h.name)
      WHERE i.main_schema_name = info.schema_name AND i.main_index_name = info.object_name;

      --if table_oid is not null, it is a main table
      IF table_oid IS NULL OR current_setting('io.ignore_ddl_in_trigger', true) = 'true' THEN
        RETURN;
      END IF;

      --TODO: this ignores the concurrently and cascade/restrict modifiers
      PERFORM
          _iobeamdb_meta_api.drop_index(
              info.schema_name,
              info.object_name
        );
  END LOOP;
END
$BODY$;

--Handles the following ddl alter table commands on hypertables:
-- ADD COLUMN, DROP COLUMN, ALTER COLUMN SET DEFAULT, ALTER COLUMN DROP DEFAULT, ALTER COLUMN SET/DROP NOT NULL
-- RENAME COLUMN
-- not supported (explicit):
-- ALTER COLUMN SET DATA TYPE
-- Other alter commands also not supported
CREATE OR REPLACE FUNCTION _iobeamdb_internal.ddl_process_alter_table()
  RETURNS event_trigger
 LANGUAGE plpgsql
  AS
$BODY$
DECLARE
  info           record;
  hypertable_row _iobeamdb_catalog.hypertable;
  found_action   BOOLEAN;
  att_row        pg_attribute;
  rec            record;
BEGIN
  FOR info IN SELECT * FROM pg_event_trigger_ddl_commands()
    LOOP

    --exit if not hypertable or inside trigger
    IF NOT _iobeamdb_internal.is_main_table(info.objid) OR current_setting('io.ignore_ddl_in_trigger', true) = 'true' THEN
      RETURN;
    END IF;

    hypertable_row := _iobeamdb_internal.hypertable_from_main_table(info.objid);

    --Try to find what was done. If you can't find it error out.
   found_action = FALSE;

    --was a column added?
    FOR att_row IN
      SELECT *
       FROM pg_attribute att
       WHERE attrelid = info.objid AND
             attnum > 0 AND
             NOT attisdropped AND
             att.attnum NOT IN (SELECT c.attnum FROM _iobeamdb_catalog.hypertable_column c WHERE hypertable_name = hypertable_row.name)
    LOOP
        PERFORM  _iobeamdb_internal.create_column_from_attribute(hypertable_row.name, att_row);
        found_action = TRUE;
    END LOOP;

    --was a column deleted
    FOR rec IN
      SELECT name
      FROM _iobeamdb_catalog.hypertable_column c
      INNER JOIN pg_attribute att ON (attrelid = info.objid AND att.attnum = c.attnum AND attisdropped) --do not match on att.attname here. it gets mangled
      WHERE hypertable_name = hypertable_row.name
    LOOP
        PERFORM _iobeamdb_meta_api.drop_column(
            hypertable_row.name,
            rec.name
        );
        found_action = TRUE;
    END LOOP;

    --was a column renamed
    FOR rec IN
      SELECT c.name old_name, att.attname new_name
      FROM _iobeamdb_catalog.hypertable_column c
      LEFT JOIN pg_attribute att ON (attrelid = info.objid AND att.attnum = c.attnum AND NOT attisdropped)
      WHERE hypertable_name = hypertable_row.name AND c.name IS DISTINCT FROM att.attname
    LOOP
        PERFORM _iobeamdb_meta_api.alter_table_rename_column(
            hypertable_row.name,
            rec.old_name,
            rec.new_name
        );
        found_action = TRUE;
    END LOOP;

    --was a colum default changed
    FOR rec IN
      SELECT name, _iobeamdb_internal.get_default_value_for_attribute(att) AS new_default_value
      FROM _iobeamdb_catalog.hypertable_column c
      LEFT JOIN pg_attribute att ON (attrelid = info.objid AND attname = c.name AND att.attnum = c.attnum AND NOT attisdropped)
      WHERE hypertable_name = hypertable_row.name AND _iobeamdb_internal.get_default_value_for_attribute(att) IS DISTINCT FROM c.default_value
    LOOP
        PERFORM _iobeamdb_meta_api.alter_column_set_default(
            hypertable_row.name,
            rec.name,
            rec.new_default_value
        );
        found_action = TRUE;
    END LOOP;

    --was the not null flag changed?
    FOR rec IN
      SELECT name, attnotnull AS new_not_null
      FROM _iobeamdb_catalog.hypertable_column c
      LEFT JOIN pg_attribute att ON (attrelid = info.objid AND attname = c.name AND att.attnum = c.attnum AND NOT attisdropped)
      WHERE hypertable_name = hypertable_row.name AND attnotnull != c.not_null
    LOOP
        PERFORM _iobeamdb_meta_api.alter_column_set_not_null(
            hypertable_row.name,
            rec.name,
            rec.new_not_null
        );
        found_action = TRUE;
    END LOOP;

    --type changed
    FOR rec IN
      SELECT name
      FROM _iobeamdb_catalog.hypertable_column c
      INNER JOIN pg_attribute att ON (attrelid = info.objid AND attname = c.name AND att.attnum = c.attnum AND NOT attisdropped)
      WHERE hypertable_name = hypertable_row.name AND att.atttypid IS DISTINCT FROM c.data_type
    LOOP
      RAISE EXCEPTION 'ALTER TABLE ... ALTER COLUMN SET DATA TYPE  not supported on hypertable %', info.objid::regclass
      USING ERRCODE = 'IO101';
    END LOOP;

    IF NOT found_action THEN
      RAISE EXCEPTION 'Unknown alter table action on %', info.objid::regclass
      USING ERRCODE = 'IO101';
    END IF;

  END LOOP;
  END
$BODY$;

CREATE OR REPLACE FUNCTION _iobeamdb_internal.is_hypertable(
    schema_name NAME,
    table_name  NAME
)
    RETURNS BOOLEAN LANGUAGE PLPGSQL VOLATILE AS
$BODY$
BEGIN
     return exists(select 1 from _iobeamdb_catalog.hypertable where main_schema_name = schema_name and  main_table_name=table_name);
END
$BODY$;

--Handles drop table command
CREATE OR REPLACE FUNCTION _iobeamdb_internal.ddl_process_drop_table()
        RETURNS event_trigger LANGUAGE plpgsql AS $BODY$
DECLARE
    obj record;
BEGIN
    IF current_setting('io.ignore_ddl_in_trigger', true) = 'true' THEN
        RETURN;
    END IF;

    FOR obj IN SELECT * FROM pg_event_trigger_dropped_objects()
    LOOP
        IF tg_tag = 'DROP TABLE' AND _iobeamdb_internal.is_hypertable(obj.schema_name, obj.object_name) THEN
            PERFORM _iobeamdb_meta_api.drop_hypertable(obj.schema_name, obj.object_name);
        END IF;
    END LOOP;
END
$BODY$;