From: Andrew Gierth <andrew@tao11.riddles.org.uk>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgresql.org
Subject: Re: A really subtle lexer bug
Date: Thu, 23 Aug 2018 16:29:23 +0100
Message-ID: <871sap1658.fsf@news-spur.riddles.org.uk> (raw)
In-Reply-To: <18470.1535036115@sss.pgh.pa.us>
References: <87va851ppl.fsf@news-spur.riddles.org.uk>
<87ftz90yma.fsf@news-spur.riddles.org.uk>
<18470.1535036115@sss.pgh.pa.us>
>>>>> "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes:
>> Patch attached.
>> This fixes two bugs: first the mis-lexing of two-char ops as mentioned
>> originally; second, the O(N^3) lexing time of strings of - or +
>> characters is reduced to O(N^2) (in practice it's better than O(N^2)
>> once N gets large because the bison stack gets blown out, ending the
>> loop early).
Tom> Looks reasonable offhand (didn't test). A couple of thoughts:
Tom> * Some regression tests exercising these code paths might be a
Tom> good thing.
Agreed. Any preferences where they should go?
Tom> * There should likely be a comment near where EQUALS_GREATER and
Tom> friends are defined, pointing out that if we add any more
Tom> multi-character operators with special precedences, this code has
Tom> to be taught about them.
Agreed; will do this.
--
Andrew (irc:RhodiumToad)
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To: pgsql-hackers@postgresql.org
Cc: andrew@tao11.riddles.org.uk, tgl@sss.pgh.pa.us
Subject: Re: A really subtle lexer bug
In-Reply-To: <871sap1658.fsf@news-spur.riddles.org.uk>
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