Does JDBC's executeBatch() execute statements in parallel or one after the other

Question

I want to delete entries from multiple tables in a postgreSQL DB. The tables have foreign key constraints, so I need to delete them in particular order only (otherwise delete will fail).

I am thinking of adding them to a batch and running executeBatch()

I understand that executeBatch submits all the statements together to driver but how are statements executed? Is the order of deletion will be maintained as per order of adding to the batch? I can't find it mentioned in API doc

Answer 1

The JDBC 4.3 specification explicitly specifies the behaviour of a batch execution in section 14.1.2 Successful Execution:

Batch commands are executed serially (at least logically) in the order in which they were added to the batch.

and

The entries in the array are ordered according to the order in which the commands were processed (which, again, is the same as the order in which the commands were originally added to the batch).

The "at least logically" gives databases some leeway to reorder things as an optimization, as long as the resulting behaviour is the same as if the batch was executed in the specified order. Execution in-order is also necessary to ensure the returned update counts match, and for exception behaviour.