dblink_send_query sends a query to be executed asynchronously, that is, without immediately waiting for the result. There must not be an async query already in progress on the connection.
After successfully dispatching an async query, completion status can be checked with
dblink_is_busy, and the results are ultimately collected with
dblink_get_result. It is also possible to attempt to cancel an active async query using
Name of the connection to use.
The SQL statement that you wish to execute in the remote database, for example select * from pg_class.