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Re: Poorly designed tsearch NOTICEs

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>, Teodor Sigaev <teodor(at)sigaev(dot)ru>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Poorly designed tsearch NOTICEs
Date: 2007-11-28 00:03:16
Message-ID: 14785.1196208196@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Last month I complained:
> regression=# SELECT plainto_tsquery('the any'); 
> NOTICE:  query contains only stopword(s) or doesn't contain lexeme(s), ignored
>  plainto_tsquery 
> -----------------
 
> (1 row)

> regression=# select ''::tsquery;
> NOTICE:  tsearch query doesn't contain lexeme(s): ""
>  tsquery 
> ---------
 
> (1 row)

> IMHO, it's really bad design to have this sort of NOTICE emitted by
> tsquery input.  Even if an application uses numnode() or querytree() or
> something similar to detect bogus queries, it's going to have its logs
> cluttered with these notices.

> I could see having the @@ operator emit the notice if the query is
> actually used for searching --- though I'm not quite sure how to get it
> to come out only once per query ... maybe we could put it into the index
> consistent() functions somehow?

I experimented with this and found out that it works all right for GIN
indexes, if the NOTICE is put into gin_extract_query(); that seems to be
called just once per GIN index search.  However, the only possible place
to put it in GIST tsearch support would be in the consistent() routines,
and that's no good because those will be called once per entry on the
index's root page --- so you get multiple copies of the NOTICE.

So it seems that the practical alternatives are:

1. Leave these notices where they are.  Expect complaints from people
who would rather not have their logs cluttered with 'em.

2. Remove the notices altogether.  Expect complaints from people who
get no matches on queries that they don't realize are all-stopwords.

3. Remove the notices from the input routines, and put one into
gin_extract_query only.  We'll still get complaints as in #2, but
only from people using GIST indexes or no index at all for searching.

None of these are really terribly attractive, but I'm kinda leaning
to #2 myself.  I'm not convinced that it's the province of the DB to be
issuing messages like this.  In a lot of common scenarios, NOTICEs
aren't going to be seen by the actual person entering the query anyway,
because there are layers of software between him and the DB.  All they
will accomplish is to bloat some logs somewhere.

Comments?

			regards, tom lane

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