Re: Is the query engine always smart enough to know when to generate an internal CTE on a query?

Hi Dan,

I think an explicit CTE is worth a try.

Best Regards,

Peter.
647-456-3124
[email protected]

________________________________
From: MIDRANGE-L <midrange-l-bounces-+hD5IHI5Xscn3HwCXmMcX9BPR1lH4CV8@public.gmane.org> on behalf of Dan Bale via MIDRANGE-L <[email protected]>
Sent: Thursday, August 06, 2026 17:23
To: Midrange Systems Technical Discussion <[email protected]>
Cc: Dan Bale <dan.bale-EkiVQpMPPJH8R359/[email protected]>
Subject: Is the query engine always smart enough to know when to generate an internal CTE on a query?

We've got a long-running query that has a tendency to get canceled because it hits our temporary storage threshold.

The current table has a lot of conditions in the WHERE clause on the primary table that greatly narrow the rows from that table.  There are also 15 left joins on that primary table.  I've thought about modifying the query to use a CTE on the primary table and move the conditions in the WHERE clause to the CTE.

I'm just wondering if the query engine optimizes this anyway without the explicit CTE.  Thoughts?

- Dan Bale
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