Lu, Huayi a24ca60074 DWS DEVELOPER 811 version

Reviewed-by: Hasko, Vladimir <vladimir.hasko@t-systems.com>
Co-authored-by: Lu, Huayi <luhuayi@huawei.com>
Co-committed-by: Lu, Huayi <luhuayi@huawei.com>

2023-01-19 13:37:49 +00:00

5.8 KiB

Raw Permalink Blame History

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

1
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.

1
2
3
4
5
EXECUTE DIRECT ON(dn_6001_6002) 'select count(*) from tpcds.customer_address';
 count 
-------
 16922
(1 row)

Parent topic: DCL Syntax

5.8 KiB Raw Permalink Blame History