EXECUTE DIRECT
EXECUTE DIRECT
7
SQL - Language Statements
EXECUTE DIRECT
Launch queries directly to dedicated nodes
EXECUTE DIRECT ON ( nodename [, ... ] )
query
Description
EXECUTE DIRECT is a SQL command specially created for
Postgres-XL to allow launching queries directly
on one of the nodes determined by a list of nodes nodelist.
EXECUTE DIRECT is currenlty limited to be used on 1 node at a time
only.
The usage of transaction queries
(BEGIN, COMMIT...), DDL, and DML
(INSERT, UPDATE, DELETE
) is forbidden to avoid data inconsistency among nodes
in the cluster. EXECUTE DIRECT usage is also limited to superusers.
Either a Coordinator or Datanode can be selected by its node name.
EXECUTE DIRECT allows the usage of the following utility commands
on remote nodes: CREATE TABLESPACE, DROP TABLESPACE.
Parameters
nodename
This mandatory clause specifies the node name on where to launch
query. When specifying
multiple nodes, node names have to be separated by a comma.
query
This mandatory clause specifies the raw query to launch
on specified node list nodelist.
Examples
Select some data in a given table tenk1 on remote Datanode named dn1:
EXECUTE DIRECT ON NODE dn1 'SELECT * FROM tenk1 WHERE col_char = ''foo''';
Select local timestamp of a remote node named coord2:
EXECUTE DIRECT ON coord2 'select clock_timestamp()';
Select list of tables of a remote node named dn50:
EXECUTE DIRECT ON dn50 'select tablename from pg_tables';
Compatibility
EXECUTE DIRECT does not conform to the
SQL standards, it is a Postgres-XL specific command.