[hibernate-dev] Stored procedure improvement

[Steve Ebersole]

Well as my todo comment says:

// todo : how to identify calls which should be in the form `{? = call
procName...}` ??? (note leading param marker)

//        more than likely this will need to be a method on the native
API.  I can see this as a trigger to
//    both: (1) add the `? = ` part and also (2) register a REFCURSOR
parameter for DBs (Oracle, PGSQL) that
//    need it.

:)


On Mon, Feb 15, 2016 at 7:54 AM Vlad Mihalcea <mihalcea.vlad at gmail.com>
wrote:

> Hi,
>
> While writing the stored procedure section, I found a way to improve the
> current implementation to FUNCTIONS as well.
>
> Considering the following function:
>
> CREATE FUNCTION fn_post_comments(postId integer)
> RETURNS integer
> DETERMINISTIC
> READS SQL DATA
> BEGIN
>     DECLARE commentCount integer;
>     SELECT COUNT(*) INTO commentCount
>     FROM post_comment
>     WHERE post_comment.post_id = postId;
>     RETURN commentCount;
> END
>
> We could call this function and fetch the result ith plain-old JDBC:
>
> session.doWork(connection -> {
>     try (CallableStatement function = connection.prepareCall("{ ? =
> call fn_count_comments(?) }")) {
>         function.registerOutParameter(1, Types.INTEGER);
>         function.setInt(2, 1);
>         function.execute();
>         int commentCount = function.getInt(1);
>         assertEquals(2, commentCount);
>     }
> });
>
> When using the JPA 2.1 API:
>
> StoredProcedureQuery query =
> entityManager.createStoredProcedureQuery("fn_count_comments");
> query.registerStoredProcedureParameter("postId", Long.class,
> ParameterMode.IN);
>
> query.setParameter("postId", 1L);
>
> Long commentCount = (Long) query.getSingleResult();
>
> We get a "PROCEDURE fn_count_comments does not exist" exception because the
> SQL statement is built as "{call fn_count_comments(?)}" instead of "{ ? =
> call fn_count_comments(?) }".
> I think we could define a hint like this:
>
> query.setHint(QueryHints.HINT_CALL_FUNCTION, true);
>
> So we could adjust the callable statement to work like a function.
>
> What do you think of this?
>
> Vlad
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