Re: [PATCH] Microvacuum for gist.

From: Teodor Sigaev <teodor(at)sigaev(dot)ru>
To: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
Cc: Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCH] Microvacuum for gist.
Date: 2015-09-17 16:44:36
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> But I don't understand this comment:
> + /*
> + * While we delete only one tuple at once we could mix calls
> + * PageIndexTupleDelete() here and PageIndexMultiDelete() in
> + * gistRedoPageUpdateRecord()
> + */
> Does this mean:
> Since we delete only one tuple per WAL record here, we can call
> PageIndexTupleDelete() here and re-play it with PageIndexMultiDelete() in
> gistRedoPageUpdateRecord()

yes. The problem was when we delete tuples with offset (2,4,6) with
PageIndexMultiDelete() we will delete exctly pointed tuples. Bur if we delete
tuple by PageIndexTupleDelete() with offset 2 then 4-th tuple will be moved 3 3
and 6 become 5. So, next tuple to delete now is 3 and we should call
PageIndexTupleDelete(3) and so on. And bug was: we deleted tuples in
ginpagevacuum with a help of PageIndexMultiDelete() and write to WAL his
argument, and recovery process uses PageIndexTupleDelete() without correcting

Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru

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