From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Some regular-expression performance hacking
Date: Tue, 23 Feb 2021 12:52:28 -0500
Message-ID: <3875615.1614102748@sss.pgh.pa.us> (raw)
In-Reply-To: <3874948.1614101949@sss.pgh.pa.us>
References: <1340281.1613018383@sss.pgh.pa.us>
<20210223173437.b3ywijygsy6q42gq@alap3.anarazel.de>
<3874948.1614101949@sss.pgh.pa.us>
I wrote:
> Hmph. There's an "assert(depth >= 0)" immediately in front of that,
> so I'm not looking too kindly on the compiler thinking it's smarter
> than I am. Do you have a suggestion on how to shut it up?
On reflection, maybe the thing to do is convert the assert into
an always-on check, "if (depth < 0) return false". The assertion
is essentially saying that there's no arc leading directly from
the pre state to the post state. Which there had better not be,
or a lot of other stuff is going to go wrong; but I suppose there's
no way to explain that to gcc. It is annoying to have to expend
an always-on check for a can't-happen case, though.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, andres@anarazel.de, pgsql-hackers@lists.postgresql.org
Subject: Re: Some regular-expression performance hacking
In-Reply-To: <3875615.1614102748@sss.pgh.pa.us>
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