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  • create-index should run analyze after creating index · 7 ✖

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  • CONTRIBUTOR · 7 ✖
id html_url issue_url node_id user created_at updated_at ▲ author_association body reactions issue performed_via_github_app
1009548580 https://github.com/simonw/sqlite-utils/issues/365#issuecomment-1009548580 https://api.github.com/repos/simonw/sqlite-utils/issues/365 IC_kwDOCGYnMM48LH0k fgregg 536941 2022-01-11T02:43:34Z 2022-01-11T02:43:34Z CONTRIBUTOR

thanks so much! always a pleasure to see how you work through these things

 
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 create-index should run analyze after creating index 1096558279  
1008275546 https://github.com/simonw/sqlite-utils/issues/365#issuecomment-1008275546 https://api.github.com/repos/simonw/sqlite-utils/issues/365 IC_kwDOCGYnMM48GRBa fgregg 536941 2022-01-09T11:01:15Z 2022-01-09T13:37:51Z CONTRIBUTOR

i don’t want to be such a partisan for analyze, but the query planner deciding not to use an index based on information collected by analyze is not necessarily a bug, but could be the correct choice.

<s>the original poster in that stack overflow doesn’t say there’s a performance regression </s>

 
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 create-index should run analyze after creating index 1096558279  
1008166084 https://github.com/simonw/sqlite-utils/issues/365#issuecomment-1008166084 https://api.github.com/repos/simonw/sqlite-utils/issues/365 IC_kwDOCGYnMM48F2TE fgregg 536941 2022-01-08T22:32:47Z 2022-01-08T22:32:47Z CONTRIBUTOR

or using “ pragma optimize”

 
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 create-index should run analyze after creating index 1096558279  
1008164786 https://github.com/simonw/sqlite-utils/issues/365#issuecomment-1008164786 https://api.github.com/repos/simonw/sqlite-utils/issues/365 IC_kwDOCGYnMM48F1-y fgregg 536941 2022-01-08T22:24:19Z 2022-01-08T22:24:19Z CONTRIBUTOR

the out-of-date scenario you describe could be addressed by automatically adding an analyze to the insert or convert commands if they implicate an index

 
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 create-index should run analyze after creating index 1096558279  
1008164116 https://github.com/simonw/sqlite-utils/issues/365#issuecomment-1008164116 https://api.github.com/repos/simonw/sqlite-utils/issues/365 IC_kwDOCGYnMM48F10U fgregg 536941 2022-01-08T22:18:57Z 2022-01-08T22:18:57Z CONTRIBUTOR

the table with the query ran so bad was about 50k.

i think the scenario should not be worse than no stats.

i also did not know that sqlite was so different from postgres and needed an explicit analyze call.

 
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 create-index should run analyze after creating index 1096558279  
1008161965 https://github.com/simonw/sqlite-utils/issues/365#issuecomment-1008161965 https://api.github.com/repos/simonw/sqlite-utils/issues/365 IC_kwDOCGYnMM48F1St fgregg 536941 2022-01-08T22:02:56Z 2022-01-08T22:02:56Z CONTRIBUTOR

for options 2 and 3, i would worry about discoverablity.

in other db’s it is not necessary to explicitly call analyze for most indices. ie for postgres

The system regularly collects statistics on all of a table's columns. Newly-created non-expression indexes can immediately use these statistics to determine an index's usefulness.

i suppose i would propose raising a warning if the stats table is created that explains what is going on and informs users about a —no-analyze argument.

 
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 create-index should run analyze after creating index 1096558279  
1007636709 https://github.com/simonw/sqlite-utils/issues/365#issuecomment-1007636709 https://api.github.com/repos/simonw/sqlite-utils/issues/365 IC_kwDOCGYnMM48D1Dl fgregg 536941 2022-01-07T18:28:33Z 2022-01-07T18:29:43Z CONTRIBUTOR

i added an index to one table with sqlite-utils, and then a query that used to take about 1 second started taking hundreds of seconds.

running analyze got me back to sub second speed.

 
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 create-index should run analyze after creating index 1096558279  

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