From: Victor Drobny <v.drobny@postgrespro.ru>
To: Alexey Chernyshov <a.chernyshov@postgrespro.ru>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: new function for tsquery creartion
Date: Fri, 13 Oct 2017 16:55:12 +0300
Message-ID: <3e1b0851d3a6a2da42f78d31cc241d0b@postgrespro.ru> (raw)
In-Reply-To: <20171013163732.1bb85695@PostgresPro-A-Chernyshov>
References: <fe931111ff7e9ad79196486ada79e268@postgrespro.ru>
<CA+TgmoYSBLFAq14ePMWC=JBQ4D4Crt08emkcDPa65SQ6sbVAoQ@mail.gmail.com>
<CAEepm=2S-rXC-G3iGSJLKwThF2v9zWG0pJB4R6v5LVVphwQkRw@mail.gmail.com>
<69234700d26674fc7c171e48b850824c@postgrespro.ru>
<20171013163732.1bb85695@PostgresPro-A-Chernyshov>
List-Unsubscribe: <mailto:majordomo@postgresql.org?body=unsub%20pgsql-hackers>
On 2017-10-13 16:37, Alexey Chernyshov wrote:
> Hi all,
> I am extending phrase operator <n> is such way that it will have <n,m>
> syntax that means from n to m words, so I will use such syntax (<n,m>)
> further. I found that a AROUND(N) b is exactly the same as a <-N,N> b
> and it can be replaced while parsing. So, what do you think of such
> idea? In this patch I have noticed some unobvious behavior.
Thank you for the interest and review!
> # select to_tsvector('Hello, cat world!') @@ queryto_tsquery('cat
> AROUND(1) cat') as match;
> match
> -------
> t
>
> cat AROUND(1) cat is the same is "cat <1> cat || cat <0> cat" and:
>
> # select to_tsvector('Hello, cat world!') @@ to_tsquery('cat <0> cat');
> ?column?
> -------
> t
>
> It seems to be a proper logic behavior but it is a possible pitfall,
> maybe it should be documented?
It is a tricky question. I think that this interpretation is confusing,
so
better to make it as <-N, -1> and <1, N>.
> But more important question is how AROUND() operator should handle stop
> words? Now it works as:
>
> # select queryto_tsquery('cat <2> (a AROUND(10) rat)');
> queryto_tsquery
> ------------------
> 'cat' <12> 'rat'
> (1 row)
>
> # select queryto_tsquery('cat <2> a AROUND(10) rat');
> queryto_tsquery
> ------------------------
> 'cat' AROUND(12) 'rat'
> (1 row)
>
> In my opinion it should be like:
> cat <2> (a AROUND(10) rat) == cat <2,2> (a <-10,10> rat) == cat <-8,12>
> rat
I think that correct version is:
cat <2> (a AROUND(10) rat) == cat <2,2> (a <-10,10> rat) == cat <-2,12>
rat.
> cat <2> a AROUND(10) rat == cat <2,2> a <-10,10> rat = cat <-8, 12>
> rat
It is a problem indeed. I did not catch it during implementation. Thank
you
for pointing it out.
> Now <n,m> operator can be replaced with combination of phrase
> operator <n>, AROUND(), and logical operators, but with <n,m> operator
> it will be much painless. Correct me, please, if I am wrong.
I think that <n,m> operator is more general than around(n) so the last
one
should be based on yours. However, i think, that taking negative
parameters
is not the best idea because it is confusing. On top of that it is not
so
necessary and i think it won`t be popular among users.
It seems to me that AROUND operator can be easily implemented with
<n,m>,
also, it helps to avoid problems, that you showed above.
--
Victor Drobny
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: v.drobny@postgrespro.ru, a.chernyshov@postgrespro.ru, thomas.munro@enterprisedb.com, robertmhaas@gmail.com
Subject: Re: new function for tsquery creartion
In-Reply-To: <3e1b0851d3a6a2da42f78d31cc241d0b@postgrespro.ru>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox