Oracle PL/SQL for DBAs

Bulk Fetching the Criteria

Because my table function guarantees that records will be grouped by region, I can safely assume that any time the region ID value of a fetched record changes, I will have moved on to the next region. And the first thing I want to do for each region is load its repeat-order criteria into a PL/SQL associative array. I’ll accomplish this using a cursor as shown here.

    CURSOR curs_get_criteria ( cp_region NUMBER ) IS
      SELECT *
        FROM repeat_order_criteria
       WHERE region_id = cp_region;

Then, within the function, I implement a simple “last region id” check to see when the value changes, and, if it does, I bulk load the criteria:

    -- if it's a new region...
    IF NVL(v_last_region,0) <> v_order.region_id THEN

      -- set the local region ID and bulk load
      -- its criteria
      v_last_region := v_order.region_id;
      OPEN curs_get_criteria(v_order.region_id);
      FETCH curs_get_criteria BULK COLLECT INTO v_criteria;
      CLOSE curs_get_criteria;

    END IF;  -- new region

This exposes another benefit of table functions —the ability to implement focused data access within the function itself. This means that the database can focus on getting the orders with one query and the repeat criteria with another.

Getting back to the function, the pseudo-code looks like this now that I’ve added the query to get the criteria:

 BEGIN -- for every order... LOOP FETCH p_curs INTO v_order; EXIT WHEN p_curs%NOTFOUND; IF first record or new region THEN Load region criteria END IF; IF it's a repeat order then PIPE ROW( ...