Re: Do we want a hashset type?

From: Tom Dunstan <pgsql(at)tomd(dot)cc>
To: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, Joel Jacobson <joel(at)compiler(dot)org>, jian he <jian(dot)universality(at)gmail(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: Do we want a hashset type?
Date: 2023-06-14 23:57:31
Message-ID: CAPPfruySQDMaV41Tj8yBFGF6L0cd2Brr8L1eZPbosR=HKX5ysw@mail.gmail.com
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On Wed, 14 Jun 2023 at 19:14, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
wrote:

> > ...So we'd want the same index usage as
> > =ANY(array) but would like faster row checking than we get with an array
> > when other indexes are used.
>
> We kinda already do this since PG14 (commit 50e17ad281), actually. If
> the list is long enough (9 values or more), we'll build a hash table
> during query execution. So pretty much exactly what you're asking for.
>

Ha! That is great. Unfortunately we can't rely on it as we have customers
using versions back to 12. But good to know that it's available when we
bump the required versions.

Thanks

Tom

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