avamingli commented on PR #1525: URL: https://github.com/apache/cloudberry/pull/1525#issuecomment-3757913403
> I suggest join_collapse_limit=8 to reduce the difference from PostgreSQL 14, but you can consider slightly larger values. In the table below there are time and memory consumption to process the query from the test. > > join_collapse_limit Query processing time, ms Backend memory usage > 8 96 52 MB > 9 230 88 MB > 10 653 210 MB > 11 1269 394 MB > 12 2994 889 MB > 13 9003 2.4 GB > 14 27245 7.3 GB > 15 80904 22 GB > 16 670578 66 GB > 17 4158314 200 GB > Query processing time was got using `\timing on` in psql. Backend memory usage was measured at the end of the `planner` function I’m surprised that the planner consumes so much memory — typically it uses very little. Your test results are surprising to me. Could you share the complete test setup so others can reproduce it? Another point is that this parameter is intended to generate better query plans. Reducing it could lead to worse plans. Memory usage during the planning phase is usually negligible compared to execution memory. We need to verify in standard benchmarks whether lowering this parameter causes any performance regression. Typically, we should test it with TPCDS at 1TB scale. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
