Re: Inquiry on Generating Bitmaps from Filter Conditions in Index Scans

Thanks. Our project is at https://github.com/tensorchord/pgvecto.rs. A custom index is implemented for the vector similarity search, which implements `amgettuples` with direction support to provide candidates for the order by clause. 

And we want to inject the filter condition using bitmap into the amgettuples process, instead of checking the tuples one by one to accelerate the whole process. 

Best
Jinjing Zhou
> From: "Tomas Vondra"<tomas(dot)vondra(at)enterprisedb(dot)com>
> Date: Mon, Nov 20, 2023, 18:52
> Subject: Re: Inquiry on Generating Bitmaps from Filter Conditions in Index Scans
> To: "Jinjing Zhou"<allenzhou(at)tensorchord(dot)ai>, "pgsql-hackers(at)lists(dot)postgresql(dot)org"<pgsql-hackers(at)lists(dot)postgresql(dot)org>
> On 11/19/23 18:19, Jinjing Zhou wrote:
> > Hi hackers, 
> >
> > I hope this message finds you well. I am reaching out to seek guidance
> > on a specific aspect of PostgreSQL's index scanning functionality.
> >
> > I am currently working on a vector search extension for postgres, where
> > I need to generate bitmaps based on filter conditions during an index
> > scan. The goal is to optimize the query performance by efficiently
> > identifying the rows that meet the given criteria.
> >
> > The query plan looks like this
> >
> > Index Scan using products_feature_idx on products  (cost=0.00..27.24
> > rows=495 width=12)
> >          Order By: (feature <-> '[0.5, 0.5, 0.5]'::vector)
> >          Filter: ((price > '0.2'::double precision) AND (price <=
> > '0.7'::double precision))
> >
> >
> > We have a custom index for the order by clause on the feature column.
> > Now we want to utilize the index on other columns like price column. We
> > want to access the bitmap of price column's filter condition in the
> > feature column index. Is there any way I can achieve this goal?
> >
> > Any help or guidance is appreciated!
> >
>
> I suppose you'll need to give more details about what exactly are you
> trying to achieve, what you tried, maybe some code examples, etc. Your
> question is quite vague, and it's unclear what "bitmaps generated on
> filter conditions" or "custom index" means.
>
> regards
>
> --
> Tomas Vondra
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company