How to diagnose and fix the 2001 no_additional_dynamic_result_sets_returned error code in Postgres.

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The 2001 error code in PostgreSQL, corresponding to no_additional_dynamic_result_sets_returned, is associated with a situation where a command was expected to return additional result sets, but no more are available. This can occur in the context of stored procedures that have the capability to return multiple result sets, and a client attempts to fetch additional result sets beyond what the procedure can provide.

To diagnose and fix this issue, you would typically need to:

  1. Review the procedure or function that’s supposed to return multiple result sets, ensuring that it’s designed correctly to provide the expected number of result sets.
  2. Check the client application code that is fetching the result sets to ensure it is not attempting to retrieve more result sets than what the procedure is designed to return.

Here are some examples of how you might write a stored procedure to return multiple result sets and how to fetch them:

Example of a stored procedure that returns multiple result sets:

CREATE OR REPLACE PROCEDURE get_multiple_result_sets()
LANGUAGE plpgsql
AS $$
BEGIN
    -- First result set
    RETURN QUERY SELECT * FROM table1;

    -- Second result set
    RETURN QUERY SELECT * FROM table2;

    -- If there were a third, it would be here
    -- RETURN QUERY SELECT * FROM table3;
END;
$$;

Example of fetching result sets in a client application (pseudo-code):

CALL get_multiple_result_sets();

-- Fetch first result set
WHILE (FETCH NEXT FROM result_set1)
    PROCESS row

-- Fetch second result set
WHILE (FETCH NEXT FROM result_set2)
    PROCESS row

-- Attempting to fetch a third result set would result in the 2001 error
-- because the procedure only provides two result sets

To fix the 2001 error, you would need to ensure that the client code does not attempt to fetch more result sets than what the stored procedure provides. If the procedure is intended to return additional result sets, you would need to modify the procedure to include the additional RETURN QUERY statements.

For more information on working with stored procedures and handling result sets in PostgreSQL, you can refer to the official PostgreSQL documentation.

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