Hi Jerry,

Without knowing more about the specific query plan and IRIS setup it would be hard to know what's going on - I would highly recommend reaching out to the WRC about this if you are able. I will note that TUNE TABLE has had significant functionality improvements since IRIS version 2021.2 (see https://community.intersystems.com/post/20212-sql-feature-spotlight-smar...) , it's possible you are missing a bug fix; again WRC would be the best point of contact. Best of luck!

Following up on this from a recent customer conversation: the current best practices that we have settled on has been disabling exportselectivity as in Ben De Boe's post (https://community.intersystems.com/post/cicd-iris-sql), alongside ensuring AdaptiveMode is turned on (https://docs.intersystems.com/iris20243/csp/docbook/Doc.View.cls?KEY=RAC...). For now this will ensure that initially collected stats aren't overwritten, and once table statistics are collected automatically this should be completely "hands off".

Great breakdown - just adding that in the terms of the documentation, the "right side" of the && operator in this case is "1". The = sign and everything after it is part of another operation and is not considered in this context.