distributed_exec()

This procedure is used on an access node to execute a SQL command across the data nodes of a distributed database. For instance, one use case is to create the roles and permissions needed in a distributed database.

The procedure can run distributed commands transactionally, so a command is executed either everywhere or nowhere. However, not all SQL commands can run in a transaction. This can be toggled with the argument transactional. Note if the execution is not transactional, a failure on one of the data node will require manual dealing with any introduced inconsistency.

Note that the command is not executed on the access node itself and it is not possible to chain multiple commands together in one call.

Required Arguments

NameTypeDescription
queryTEXTThe command to execute on data nodes.

Optional Arguments

NameTypeDescription
node_listARRAYAn array of data nodes where the command should be executed. Defaults to all data nodes if not specified.
transactionalBOOLEANAllows to specify if the execution of the statement should be transactional or not. Defaults to TRUE.

Sample Usage

Create the role testrole across all data nodes in a distributed database:

CALL distributed_exec($$ CREATE USER testrole WITH LOGIN $$);

Create the role testrole on two specific data nodes:

CALL distributed_exec($$ CREATE USER testrole WITH LOGIN $$, node_list => '{ "dn1", "dn2" }');

Create new databases dist_database on data nodes, which requires to set transactional to FALSE:

CALL distributed_exec('CREATE DATABASE dist_database', transactional => FALSE);