cartodb-postgresql/scripts-available/CDB_GhostTables.sql

-- Enqueues a job to run Ghost tables linking process for the provided username
CREATE OR REPLACE FUNCTION @extschema@._CDB_LinkGhostTables(username text, db_name text, event_name text) 
RETURNS void
AS $$
  if not username:
    return

  if 'json' not in GD:
    import json
    GD['json'] = json
  else:
    json = GD['json']    

  tis_config = plpy.execute("select @extschema@.CDB_Conf_GetConf('invalidation_service');")[0]['cdb_conf_getconf']
  if not tis_config:
    plpy.warning('Invalidation service configuration not found. Skipping Ghost Tables linking.')
    return

  tis_config_dict = json.loads(tis_config)
  tis_host = tis_config_dict.get('host')
  tis_port = tis_config_dict.get('port')
  tis_timeout = tis_config_dict.get('timeout', 5)
  tis_retry = tis_config_dict.get('retry', 5)
      
  client = GD.get('invalidation', None)

  while True:

    if not client:
        try:
          import redis
          client = redis.Redis(host=tis_host, port=tis_port, socket_timeout=tis_timeout)
          GD['invalidation'] = client
        except Exception as err:
          error = "client_error - %s" % str(err)
          # NOTE: no retries on connection error
          plpy.warning('Error trying to connect to Invalidation Service to link Ghost Tables: ' +  str(err))
          break

    try:
      client.execute_command('DBSCH', db_name, username, event_name)
      break
    except Exception as err:
      error = "request_error - %s" % str(err)
      client = GD['invalidation'] = None # force reconnect
      if not tis_retry:
        plpy.warning('Error calling Invalidation Service to link Ghost Tables: ' +  str(err))
        break
      tis_retry -= 1 # try reconnecting
$$ LANGUAGE 'plpythonu' VOLATILE PARALLEL UNSAFE;

-- Enqueues a job to run Ghost tables linking process for the current user
CREATE OR REPLACE FUNCTION @extschema@.CDB_LinkGhostTables(event_name text DEFAULT 'USER')
RETURNS void
AS $$
  DECLARE
    username TEXT;
    db_name TEXT;
  BEGIN
    EXECUTE 'SELECT @extschema@.CDB_Username();' INTO username;
    EXECUTE 'SELECT current_database();' INTO db_name;

    PERFORM @extschema@._CDB_LinkGhostTables(username, db_name, event_name);
    RAISE NOTICE '_CDB_LinkGhostTables() called with username=%, event_name=%', username, event_name;
  END;
$$ LANGUAGE plpgsql VOLATILE PARALLEL UNSAFE SECURITY DEFINER;

-- Trigger function to call CDB_LinkGhostTables()
CREATE OR REPLACE FUNCTION @extschema@._CDB_LinkGhostTablesTrigger()
RETURNS trigger
AS $$
  DECLARE
    ddl_tag TEXT;
  BEGIN
    EXECUTE 'DELETE FROM @extschema@.cdb_ddl_execution WHERE txid = txid_current() RETURNING tag;' INTO ddl_tag;
    PERFORM @extschema@.CDB_LinkGhostTables(ddl_tag);
    RETURN NULL;
  END;
$$ LANGUAGE plpgsql VOLATILE PARALLEL UNSAFE SECURITY DEFINER;

-- Event trigger to save the current transaction in @extschema@.cdb_ddl_execution
CREATE OR REPLACE FUNCTION @extschema@.CDB_SaveDDLTransaction()
RETURNS event_trigger
AS $$
  BEGIN
    INSERT INTO @extschema@.cdb_ddl_execution VALUES (txid_current(), tg_tag) ON CONFLICT ON CONSTRAINT cdb_ddl_execution_pkey DO NOTHING;
  END;
$$ LANGUAGE plpgsql VOLATILE PARALLEL UNSAFE SECURITY DEFINER;

-- Creates the trigger on DDL events to link ghost tables
CREATE OR REPLACE FUNCTION @extschema@.CDB_EnableGhostTablesTrigger()
RETURNS void
AS $$
  BEGIN
    DROP EVENT TRIGGER IF EXISTS link_ghost_tables;
    DROP TRIGGER IF EXISTS check_ddl_update ON @extschema@.cdb_ddl_execution;

    -- Table to store the transaction id from DDL events to avoid multiple executions
    CREATE TABLE IF NOT EXISTS @extschema@.cdb_ddl_execution(txid bigint PRIMARY KEY, tag text);

    CREATE CONSTRAINT TRIGGER check_ddl_update
    AFTER INSERT ON @extschema@.cdb_ddl_execution
    INITIALLY DEFERRED
    FOR EACH ROW
    EXECUTE PROCEDURE @extschema@._CDB_LinkGhostTablesTrigger();

    CREATE EVENT TRIGGER link_ghost_tables
    ON ddl_command_end
    WHEN TAG IN ('CREATE TABLE', 'SELECT INTO', 'DROP TABLE', 'ALTER TABLE', 'CREATE TRIGGER', 'DROP TRIGGER', 'CREATE VIEW', 'DROP VIEW', 'ALTER VIEW', 'CREATE FOREIGN TABLE', 'ALTER FOREIGN TABLE', 'DROP FOREIGN TABLE')
    EXECUTE PROCEDURE @extschema@.CDB_SaveDDLTransaction();
  END;
$$ LANGUAGE plpgsql VOLATILE PARALLEL UNSAFE;

-- Drops the trigger on DDL events to link ghost tables
CREATE OR REPLACE FUNCTION @extschema@.CDB_DisableGhostTablesTrigger()
RETURNS void
AS $$
  BEGIN
    DROP EVENT TRIGGER IF EXISTS link_ghost_tables;
    DROP TRIGGER IF EXISTS check_ddl_update ON @extschema@.cdb_ddl_execution;
    DROP TABLE IF EXISTS @extschema@.cdb_ddl_execution;
  END;
$$ LANGUAGE plpgsql VOLATILE PARALLEL UNSAFE;