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) |
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