From: Tom Lane <tgl@sss.pgh.pa.us>
To: Artur Zakirov <a.zakirov@postgrespro.ru>
cc: pgsql-hackers@postgreSQL.org
Subject: Re: Rethinking our fulltext phrase-search implementation
In-reply-to: <773bb687-1388-6c78-af23-5635a41a243d@postgrespro.ru>
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 <773bb687-1388-6c78-af23-5635a41a243d@postgrespro.ru>
Comments: In-reply-to Artur Zakirov <a.zakirov@postgrespro.ru>
	message dated "Wed, 21 Dec 2016 15:34:12 +0300"
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Date: Wed, 21 Dec 2016 09:30:07 -0500
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Artur Zakirov <a.zakirov@postgrespro.ru> writes:
> Otherwise it seems that queries like 'a <-> (b & c)' will always return 
> false. Then we need maybe some warning message.

Well, the query as written is pointless, but it could be useful with
something other than "b" and "c" as the AND-ed terms.  In this usage
"&" is equivalent to "<0>", which we know has corner-case uses.

I'm not inclined to issue any sort of warning for unsatisfiable queries.
We don't issue a warning when a SQL WHERE condition collapses to constant
FALSE, and that seems like exactly the same sort of situation.

It strikes me though that the documentation should point this out.

			regards, tom lane


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