On Tue, 30 Oct 2007, Catalin Marinas wrote:
On 30/10/2007, Richard Huxton <dev@xxxxxxxxxxxx> wrote:
Oleg Bartunov wrote:
Catalin,
what is your need ? What's wrong with this ?
postgres=# select ts_headline('1 2 3 4 5 3 4 abc abc 2 3
xyz','2'::tsquery, 'StartSel=...,StopSel=...')
;
ts_headline
-------------------------------------------
1 ...2... 3 4 5 3 4 abc abc ...2... 3 xyz
I think he want's something like: "1 2 3 ... abc 2 3 ..."
A few characters of context around each match and then ... between. Kind
of like grep -C.
That's pretty much correct (with the difference that I'd like context
of words rather than lines as in "grep" and StartSel=<b>,
StopSel=</b>).
Since the text I want a headline for might be pretty long (tens of
lines), I'd like to only show the excerpts around the matching words.
Similar to the above example:
select ts_headline('1 2 3 4 5 3 4 abc x y z 2 3', '2 & abc'::tsquery);
should give:
'1 <b>2</b> 3 4 ... 3 4 <b>abc</b> x y'
Currently, if you limit the maximum words so that 'abc' is too far, it
only highlights the first match.
ok, then you have to formalize many things - how long should be excerpts,
how much excerpts to show, etc. In tsearch2 we have get_covers() function,
which produces all excerpts like:
=# select get_covers(to_tsvector('1 2 3 4 5 3 4 abc x y z 2 3'), '2&3'::tsquery);
get_covers
------------------------------------------------
1 {1 2 3 }1 4 5 {2 3 4 abc x y z {3 2 }2 3 }3
(1 row)
Once you formalize your requirements, you can look on it and adapt to your
needs (and share with people). I think it could be nice contrib module.
Many of the search engines (including google) show the headline this
way. I think Lucene can do this as well but I've never used it to be
sure.
Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg@xxxxxxxxxx, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83
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