Excessive planner time for some queries with high statistics
От | Stuart Bishop |
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Тема | Excessive planner time for some queries with high statistics |
Дата | |
Msg-id | CADmi=6PQ9TED0sqP7Qy6L2Z5COnTdxzXBk-1c2fknwR2GPZJAg@mail.gmail.com обсуждение исходный текст |
Ответы |
Re: Excessive planner time for some queries with high statistics
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Список | pgsql-general |
I'm seeing some queries, possibly to do with using a UNIQUE index, that have fast time reported by EXPLAIN ANALYZE but the actual time as reported by \timing at 150ms+ higher. PostgreSQL 8.4.9 Simple example queries: http://paste.ubuntu.com/726131/ Table definitions: http://paste.ubuntu.com/726193/ Rewriting the query to use common table expressions worked around the original problem: http://paste.ubuntu.com/726141/ ('fixed' version of the original more complex query). We also found this problem did not occur on one of our staging systems, which had a default statistics target of 100. Lowering the statistics on the relavant columns from 1000 to 100 and reanalyzing made the overhead unnoticeable. Thoughts on IRC was this might be a regression in 8.4.9, but I haven't got earlier versions to test with at the moment. I was asked to obtain some traces but have not been able to organize getting tools on a suitable server yet. -- Stuart Bishop <stuart@stuartbishop.net> http://www.stuartbishop.net/
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