Re: Incorrect EXPLAIN ANALYZE output in bloom index docs
От | Yan Chengpeng |
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Тема | Re: Incorrect EXPLAIN ANALYZE output in bloom index docs |
Дата | |
Msg-id | B61560C1-DD55-43D3-BD40-C28ACA87430E@Outlook.com обсуждение исходный текст |
Ответы |
Re: Incorrect EXPLAIN ANALYZE output in bloom index docs
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Список | pgsql-hackers |
> On Dec 9, 2024, at 15:53, David Rowley <dgrowleyml@gmail.com> wrote: > > I was fixing up the patch in [1] with the intention of committing it > when I noticed that there are a few outdated EXPLAIN ANALYZE examples > in the documents for the bloom contrib module. > > The example outputs look like they've been created with a 100 thousand > row table, but the commands given are to insert 10 million rows into > that table. I suspect someone did a 100x on the example row count at > some point during development and forgot to update the EXPLAIN output. > > The patch I want to commit adds buffer outputs to these EXPLAINs, so I > kinda need to fix these before adding that, otherwise what I want to > add does not make any sense. > > Patch attached. I propose to backpatch this fix. > > David > <v1-0001-Doc-fix-incorrect-EXPLAIN-ANALYZE-output-for-bloo.patch> Most changes look good to me. Only two small comments here: 1. Why did the following part change from ‘never executed’ to execute. Why the previous state is `never executed`? ``` - -> Bitmap Index Scan on btreeidx2 (cost=0.00..12.04 rows=500 width=0) (never executed) + -> Bitmap Index Scan on btreeidx2 (cost=0.00..4.52 rows=11 width=0) (actual time=0.007..0.007 rows=8 loops=1) ``` 2. There is one sentence in the old one that says, `Although this query runs much faster than with either of the single indexes,we pay a penalty in index size. Each of the single-column btree indexes occupies 2 MB, so the total space neededis 12 MB, eight times the space used by the bloom index.` I think the size also needs to be changed. - Yan
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