Hi Guys,
I propose a lag (and/or lead) window function that propagates the last non-null value to the current row. Here's an example of what I mean by that: CREATE TABLE lag_test (id serial primary key, natural_key integer, somebody text); INSERT INTO lag_test(natural_key, somebody) VALUES (1, NULL), (1, 'Kirk'), (1, NULL), (2, 'Roybal'), (2, NULL), (2, NULL); /* Creates this data in the table. id natural_key somebody -- ----------- -------- 1 1 NULL 2 1 Kirk 3 1 NULL 4 2 Roybal 5 2 NULL 6 2 NULL lag_until_you_get_something(text) function should return this in the "somebody" column: id natural_key somebody -- ----------- -------- 1 1 NULL 2 1 Kirk 3 1 Kirk 4 2 Roybal 5 2 Roybal 6 2 Roybal Notice that row 6 has a value "Roybal", when the last known value was in row 4. Also, Row 1 did not get a value. */ -- Query that gets the right result for limited example data: CREATE FUNCTION last_elem (text[]) RETURNS text AS $$ SELECT $1[array_upper($1,1)]; $$ LANGUAGE SQL; SELECT id, natural_key, last_elem(string_to_array(string_agg(somebody, '|') OVER (ORDER BY natural_key, id)::text, '|')) lag_hard FROM lag_test ORDER BY natural_key, id; Sorry, I'm not a C-coder, or I'd whip this up myself and submit it. Thank you for your consideration, /Kirk
