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	Thu, 15 Dec 2016 18:25:03 -0500
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Oleg Bartunov <obartunov@gmail.com>, Teodor Sigaev <teodor@sigaev.ru>
cc: Andreas Seltenreich <seltenreich@gmx.de>, pgsql-hackers@postgresql.org
Subject: Re: [sqlsmith] Failed assertion in TS_phrase_execute
In-reply-to: <24331.1480199636@sss.pgh.pa.us>
References: <87eg1y2s3x.fsf@credativ.de> <14732.1480186277@sss.pgh.pa.us>
 <24331.1480199636@sss.pgh.pa.us>
Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Sat, 26 Nov 2016 17:33:56 -0500"
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Date: Thu, 15 Dec 2016 18:25:03 -0500
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I wrote:
>> but I notice that some normalization seems to be getting done by
>> tsqueryin:

>> regression=3D# select $$( 'sanct' & 'peter' ) <-> ( 'sanct' & 'peter' )$=
$::tsquery;
>>                                     tsquery=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
>> ------------------------------------------------------------------------=
---------------
>>  'sanct' <-> 'sanct' & 'peter' <-> 'sanct' & 'sanct' <-> 'peter' & 'pete=
r' <-> 'peter'
>> (1 row)

> BTW, it seems like that normalization is wrong.  The transformed query
> should (and does) match the string "sanct sanct peter sanct sanct peter
> peter peter", since each of the <-> pairs has a match somewhere in there.
> But I would expect the original query to be specifying that a match occurs
> at exactly one place, which of course is unsatisfiable since 'sanct' and
> 'peter' can't match the same word.

After further thought, it seems like a correct transformation would be
to replace & underneath a PHRASE operator with <0>, ie

	('a' & 'b') <N> ('c' & 'd')

becomes

	('a' <0> 'b') <N> ('c' <0> 'd')

This would have the same effect of getting rid of non-PHRASE operators
underneath a PHRASE, and it would produce what seems to me much less
surprising results, ie you get a match only when both sides of the &
can match at the same place.  Comments?

			regards, tom lane


--=20
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