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From: James Addison <[email protected]>
To: Greg Sabino Mullane <[email protected]>
Cc: [email protected]
Cc: Tom Lane <[email protected]>
Subject: Re: Question: consolidating strpos searches?
Date: Wed, 15 Jan 2025 23:58:59 +0000
Message-ID: <CALDQ5NzmGnrnCWFSu=w-myYbfRH0K-3JrY0PunMSm3+16-JJ8w@mail.gmail.com> (raw)
In-Reply-To: <CAKAnmm+YvxoQgFrQNTUm1gNh3NSHqbwie4fx--dLp7xXjdj=9Q@mail.gmail.com>
References: <CALDQ5Ny-+ZxLuJiqC11EafO11F-KVSBgWnrWqWpRt4bw1L+hhw@mail.gmail.com>
	<CAKAnmm+YvxoQgFrQNTUm1gNh3NSHqbwie4fx--dLp7xXjdj=9Q@mail.gmail.com>

On Sat, 4 Jan 2025 at 19:04, Greg Sabino Mullane <[email protected]> wrote:
>
> On Sat, Jan 4, 2025 at 12:16 PM James Addison <[email protected]> wrote:
>>
>> In the context of considering writing a patch: would the complexity of implementing such a feature for PostgreSQL be worth the potential
>> performance benefits?
>
> Probably not. As Tom said, this sounds like it should be tried as an extension.

Will do; thanks, both of you.

>> And either way, is there more I should learn about and consider?  How would I provide convincing supporting
>> evidence if I do write a patch?
>
> As this is the performance mailing list, it might help to describe the real-world problem being encountered here. There are other ways to solve this particular issue. Among them would be using OR not AND in your contrived example, using partial indexes, using pg_trgm,  using regular expressions ( i.e. WHERE value ~ '(known|suffix)' ), redesigning your table and/or queries, and outsourcing the searching of large strings to a system more suitable for it.

The example is indeed contrived, and the idea doesn't resolve a
problem I've encountered -- in fact, my interest stems from an open
TODO item to implement Boyer-Moore string search.  I began considering
how to implement multiple string pattern search in that context -- but
LIKE/ILIKE introduce a few non-trivial considerations -- notably
wildcard patterns -- compared to strpos.  Whether to require strict
ordering of search results can also be relevant, depending on the
pattern match approach (and boolean operators, as noted) involved.

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