Re: POC, WIP: OR-clause support for indexes

Hi!

On Mon, Nov 13, 2023 at 9:48 PM a.rybakina <a(dot)rybakina(at)postgrespro(dot)ru> wrote:
> These days I was porting a patch for converting or expressions to ANY to
> the choose_bitmap_and function. Unfortunately, it is not possible to
> transfer the conversion there, since expressions are processed one by
> one, as far as I saw. Therefore, I tried to make the conversion earlier
> in the generate_bitmap_or_paths function, there is just a loop bypass.
> The patch turns out to be quite complicated, in my opinion, and to be
> honest, it does not work fully yet. Also, due to the fact that the index
> for the ScalarOpExpr expression is created earlier (approximately 344
> lines in the src/backend/optimizer/path/indxpath.c file), we had to call
> the generate_bitmap_or_paths function earlier. I haven't seen yet what
> problems this could potentially lead to. Patch in the attached diff file.

It seems to me there is a confusion. I didn't mean we need to move
conversion of OR-expressions to ANY into choose_bitmap_and() function
or anything like this. My idea was to avoid degradation of plans,
which I've seen in [1]. Current code for generation of bitmap paths
considers the possibility to split OR-expressions into distinct bitmap
index scans. But it doesn't consider this possibility for
ANY-expressions. So, my idea was to enhance our bitmap scan
generation to consider split values of ANY-expressions into distinct
bitmap index scans. So, in the example [1] and similar queries
conversion of OR-expressions to ANY wouldn't affect the generation of
bitmap paths.

Links
1. https://www.postgresql.org/message-id/CAPpHfduJtO0s9E=SHUTzrCD88BH0eik0UNog1_q3XBF2wLmH6g@mail.gmail.com

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Regards,
Alexander Korotkov