Specifying a Shard Using a Hint When You Execute a SQL Statement

DDM allows you to customize a hint to specify whether SQL statements are executed on one shard or multiple shards.

The following hint formats are supported:

• SQL statement executed on one shard: /*+db=<physical_db_name>*/ <your query>;
• SQL statement executed on multiple shards: /*+db={<physical_db_name1>, <physical_db_name2>,<physical_db_name3>......}*/ <your query>;

Example:

• SQL statement executed on one shard: /*+db=test_0000*/ select * from t1;
• SQL statement executed on multiple shards: /*+db={test_0001, test_0002, test_0003}*/ select * from t2;

Constraints:

• If the SQL statement is executed on multiple shards, the value of physical_db_name must be unique.
• The hint is valid only for SELECT, DML, and TRUNCATE statements.
• The hint works only under the text protocol, rather than the Prepare protocol.