complex query - improve performance with nested arrays, bulk insert....?
604620May 23 2008 — edited May 27 2008Hello, I have an extremely complicated query, that has a structure similar to:
Overall Query
---SubQueryA
-------SubQueryB
---SubQueryB
---SubQueryC
-------SubQueryA
The subqueries themselves are slow, and having to run them multiple times is much too slow! Ideally, I would be able to run each subquery once, and then use the results. I cannot use standard oracle tables, and i would need to keep the result of the subqueries in memory.
I was thinking I write a pl/sql script that did the subqueries at the beginning and stored the results in memory. Then in the overall query, I could loop through my results in memory, and join the results of the various subqueries to one another.
some questions:
-what is the best data structure to use? I've been looking around and there are nested arrays, and there's the bulk insert functionality, but I'm not sure what is the best to you
-the advantage of the method I'm suggesting is that I only have to do each subquery once. But, when I start joining the results of the subquery to one another, will I take a performance hit? will Oracle not be able to optimize the joins?
thanks in advance!
Coop