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
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