Re: Debugging a function - what's the best way to do this quickly?

[Melvin Davidson <melvin6925@xxxxxxxxx>]

On Tue, Dec 19, 2017 at 2:24 PM, Kevin Burke <kev@xxxxxxxxxxx> wrote:

I'm writing a function that looks a little like this:

DROP FUNCTION IF EXISTS myfunction;
CREATE OR REPLACE FUNCTION myfunction(arg1 uuid,
    _symbol text,
    _start timestamp with time zone,
    _end timestamp with time zone
) RETURNS TABLE (arg5 date, arg6 float)
AS $$
WITH cte1 AS ( ... ),

cte2 AS ( ... ),

cte3 AS ( ... ),

cte4 AS ( ... ),

cte5 AS ( ... )

SELECT X as arg5, Y as arg6 FROM cte5;
$$

The function is not returning the correct results; I think the problem is in cte2 or cte3. What's the easiest way to debug this? I would like to send some test inputs through the program, observe the output from cte3, and modify the values and see if I get the correct new answers. Here are the approaches I know right now:

- Modify the function return to contain the columns for cte3. (I don't think there is a way to indicate RETURNS * or similar wildcard)

- Reload the function.

- Call the function with the test arguments, and view the resulting table. Modify/reload/rerun as appropriate.

Or:

- Copy the function to another file.

- Delete the function prologue and epilogue

- Replace every use of the input arguments with the hardcoded values I want to test with

- Run the file, making changes as necessary.

This seems pretty cumbersome. Is there an easier way I am missing? Specifically it would be neat if it was easier to visualize the intermediate steps in the query production. If there are professional tools that help with this I would appreciate pointers to those as well.

--
Kevin Burke
925.271.7005 | kev.inburke.com

You would probably want to debug the function in interactive mode to find out where you went wrong.

Both PgAdmin III and PgAdmin 4 can use the debugger from EnterpriseDB

https://www.pgadmin.org/docs/pgadmin3/1.22/debugger.html

https://www.pgadmin.org/docs/pgadmin4/dev/debugger.html

--

Melvin Davidson
I reserve the right to fantasize.  Whether or not you
wish to share my fantasy is entirely up to you.