From: Tom Lane <tgl@sss.pgh.pa.us>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: SIMILAR TO expressions translate wildcards where they shouldn't
Date: Tue, 27 May 2025 10:54:12 -0400
Message-ID: <1101508.1748357652@sss.pgh.pa.us> (raw)
In-Reply-To: <37584c1321b984a0c5c05d213ef70b869d95a12a.camel@cybertec.at>
References: <16ab039d1af455652bdf4173402ddda145f2c73b.camel@cybertec.at>
<aC_K7JPXF0AdPZqB@paquier.xyz>
<aC_p7b5H6pLICU_e@paquier.xyz>
<5498224d1d5a6a3be7f29ae7725f76162d48372f.camel@cybertec.at>
<aDVUWaoZg8cW3B9x@paquier.xyz>
<37584c1321b984a0c5c05d213ef70b869d95a12a.camel@cybertec.at>
Laurenz Albe <laurenz.albe@cybertec.at> writes:
> On Tue, 2025-05-27 at 14:57 +0900, Michael Paquier wrote:
>> With some tweaks and the tests reworked, I am finishing with the
>> reviewed version attached. What do you think?
> Thank you; I think that is good to go.
Code changes look good, but I think the test cases are too cute:
+EXPLAIN (VERBOSE, COSTS OFF) SELECT (SELECT '') SIMILAR TO '_[_[:alpha:]_]_';
+ QUERY PLAN
+---------------------------------------------------------------
+ Result
+ Output: ((InitPlan 1).col1 ~ '^(?:.[_[:alpha:]_].)$'::text)
+ InitPlan 1
+ -> Result
+ Output: ''::text
+(5 rows)
This will break whenever somebody decides it's worth optimizing
a sub-select that looks like that. I'd suggest following the
pattern
explain (costs off) select * from text_tbl where f1 similar to 'z';
QUERY PLAN
----------------------------------
Seq Scan on text_tbl
Filter: (f1 ~ '^(?:z)$'::text)
(2 rows)
which is both less noisy and less likely to change in future.
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, laurenz.albe@cybertec.at, michael@paquier.xyz, pgsql-bugs@lists.postgresql.org
Subject: Re: SIMILAR TO expressions translate wildcards where they shouldn't
In-Reply-To: <1101508.1748357652@sss.pgh.pa.us>
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