Re: [PATCH] Don't block HOT update by BRIN index

st 30. 6. 2021 v 0:31 odesílatel Josef Šimánek <josef(dot)simanek(at)gmail(dot)com> napsal:
>
> Hello!
>
> Tomáš Vondra has shared a few ideas to improve BRIN index in czech
> PostgreSQL mail list some time ago [1 , in czech only]. This is first
> try to implement one of those ideas.
>
> Currently BRIN index blocks HOT update even it is not linked tuples
> directly. I'm attaching the initial patch allowing HOT update even on
> BRIN indexed columns. This patch went through an initial review on
> czech PostgreSQL mail list [1].

I just found out current patch is breaking partial-index isolation
test. I'm looking into this problem.

> It can be viewed online (latest version) on GitHub [2] as well.
>
> - small overview
>
> 1. I have added "amhotblocking" flag to index AM descriptor set to
> "true" for all, except BRIN, index types. And later in heap_update
> method (heapam.c) I do filter attributes based on this new flag,
> instead of currently checking for any existing index.
>
> 2. I had to enhance the "RelationGetIndexAttrBitmap" function to be
> able to return a bitmap of index attribute numbers related to the new
> AM flag using "INDEX_ATTR_BITMAP_HOT_BLOCKING" filter.
> PS: Originally the "INDEX_ATTR_BITMAP_ALL" filter was used for HOT
> check update and most likely could be removed (including all logic
> related in RelationGetIndexAttrBitmap), since I have not found any
> other usage.
>
> 3. I have created an initial regression test using
> "pg_stat_get_tuples_hot_updated" to find out HOT was successful on the
> BRIN indexed column. Unfortunately "pg_stat_get_tuples_hot_updated" is
> not updated immediately and I have not found any way to enforce the
> update. Thus (at least for now) I have used a similar approach to
> stats.sql using the "wait_for_stats" function (waiting for 30 seconds
> and checking each 100ms for change).
>
> I'm attaching patch to CF 2021-07.
>
> [1] https://groups.google.com/g/postgresql-cz/c/oxA_v3H17Qg
> [2] https://github.com/simi/postgres/pull/7