EXECUTE DIRECT

Function

EXECUTE DIRECT executes an SQL statement on a specified node. Generally, the cluster automatically allocates an SQL statement to proper nodes. EXECUTE DIRECT is mainly used for database maintenance and testing.

Precautions

• Only a system administrator can run the EXECUTE DIRECT statement.
• To ensure data consistency across nodes, only the SELECT statement can be used. Transaction statements, DDL, and DML cannot be used.
• When the AVG aggregation calculation is performed on the specified DN using such statements, the result set is returned in array, for example, {4,2}. The result of sum is 4, and that of count is 2.
• Do not run the SELECT statement on nodes where CNs reside because user table data is not stored there.
• EXECUTE DIRECT cannot be nested. If the inner SQL statement to be executed is also EXECUTE DIRECT, run only the bottom-layer EXECUTE DIRECT statement.

Syntax

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EXECUTE DIRECT ON ( nodename [, ... ] ) query ;

Parameter Description

• nodename

  Specifies the node name.

  Value range: An existing node.

• query

  Specifies the query SQL statement that you want to execute.

Examples

Query records in table tpcds.customer_address on the dn_6001_6002 node:

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EXECUTE DIRECT ON(dn_6001_6002) 'select count(*) from tpcds.customer_address';
 count 
-------
 16922
(1 row)