SET EXPLAIN COMMENTS

W> Date: Sat, 3 Jun 1995 18:12:34 +0200 W> I was attempting to speed up a report (Fourgen standard), and used "set > explain on" on our test database, getting very encouraging results (*3 in > speed). Made the changes in the report, copied to the live env and timed > the old version against the new. Guess what? Little or no time > difference, in fact under certain conditions the new program was slower by > a few minutes. W> Whats happening? Am I misunderstanding, or does "set explain" not always > work? This is strange as I have used this successfully in the past. Did your development platform have a similarly loaded database? It is important that the dev db have as many rows in the relevant tables as a typical live db, since Informix and set explain will take different approaches. For example, a small production table might be sequentially scanned, but there is no noticeable performance hit until the query is run live against a much larger table. W> Another question: I created a temporary table, created an index on it and > joined to another indexed table on the respective indexed fields. "set > explain" said the join query did not use the temp table index. Why not? 1. What was the order in your "where" clause? 2. How big was the temp table? Tim --- ~ SPEED 1.40 [NR] ~ It's more than a reader. It's a message base manager!