From: Artur Zakirov <a.zakirov@postgrespro.ru>
To: Tom Lane <tgl@sss.pgh.pa.us>
To: pgsql-hackers@postgreSQL.org
Subject: Re: Rethinking our fulltext phrase-search implementation
Date: Wed, 21 Dec 2016 15:34:12 +0300
Message-ID: <773bb687-1388-6c78-af23-5635a41a243d@postgrespro.ru> (raw)
In-Reply-To: <28215.1481999808@sss.pgh.pa.us>
References: <28215.1481999808@sss.pgh.pa.us>
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Hello Tom,
On 17.12.2016 21:36, Tom Lane wrote:
>
> 4. The transformations are wrong anyway. The OR case I showed above is
> all right, but as I argued in <24331.1480199636@sss.pgh.pa.us>, the AND
> case is not:
>
> regression=# select 'a <-> (b & c)'::tsquery;
> tsquery
> ---------------------------
> 'a' <-> 'b' & 'a' <-> 'c'
> (1 row)
>
> This matches 'a b a c', because 'a <-> b' and 'a <-> c' can each be
> matched at different places in that text; but it seems highly unlikely to
> me that that's what the writer of such a query wanted. (If she did want
> that, she would write it that way to start with.) NOT is not very nice
> either:
If I'm not mistaken PostgreSQL 9.6 and master with patch
"fix-phrase-search.patch" return false for the query:
select 'a b a c' @@ 'a <-> (b & c)'::tsquery;
?column?
----------
f
(1 row)
I agree that such query is confusing. Maybe it is better to return true
for such queries?
Otherwise it seems that queries like 'a <-> (b & c)' will always return
false. Then we need maybe some warning message.
--
Artur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company
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To: pgsql-hackers@postgresql.org
Cc: a.zakirov@postgrespro.ru, tgl@sss.pgh.pa.us
Subject: Re: Rethinking our fulltext phrase-search implementation
In-Reply-To: <773bb687-1388-6c78-af23-5635a41a243d@postgrespro.ru>
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