Stephen Davies wrote:
Unfortunately, my link to the box with the test database is down due to lack
of maintenance by our local telco (Telstra) but I think that I also missed
the optional config arg to ts_headline.
The lack of link also means that I cannot confirm your findings but your logic
looks good.
Looks like ALTER DATABASE SET default_text_config='english' is what you
need.
It begs the question, however, as to why ts-headline needs to reparse the raw
text.
It needs to line up tsvector lexemes with actual characters in the text.
The tsvector is missing punctuation, any stopwords (the, it, a) as well
as being stemmed (if your dictionary does that).
Also, it's looking for a short span of words that provide the best
match. That might not be a complete match of course, and is different to
how you'd normally look to use a tsvector.
At least in my case, I am using a trigger to parse the combination of Title
and Abstract to a ts_vector field in the table row (as suggested in 12.2.2
and 12.4.3 in the doco) so that the ts_vector is already available to
ts_headline.
If ts_headline had the ability to use that pre-parsed ts_vector, my problem
would never have arisen - and the performance of ts_headline would be
improved.
Maybe. It would still have to parse the text to some degree though, just
to get the original words & punctuation into the headline.
--
Richard Huxton
Archonet Ltd
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