Re: ts_headline

Not quite:-(

It is the ts_headline with the explicit "english" configuration that "fails"
rather than the implicit "simple".

That's what is so weird.

As you say, the ts_vector has "databas" so the "english" version of
ts_headline should work - but it doesn't. The "simple" version does; despite
the above.

Weird!

Stephen

On Friday 22 February 2008 19:33, Richard Huxton wrote:
> Stephen Davies wrote:
> > OK. The first level explanation is that my default config is "simple".
>
> Aha! Actually, that's the whole explanation.
>
> > This explains the different query results as "english" reduces "database"
> > to "databas" while "simple does not reduce it at all.
>
> Exactly.
>
> > The "document" is parsed/indexed using "english" explicitly so my queries
> > nedd to be explicit also (not an issue as all "real" queries are
> > generated rather than typed).
>
> Or change your default configuration to match the one you're using.
>
> > However, I still cannot see a reason for the ts_headline results. If
> > anything, they should be the other way around.
> >
> > I suspect that ts_headline may only work properly when no configuration
> > is specified - regardless of the default setting.
>
> No. What's happening is that your tsvector representation of the
> document (which gets indexed) contains lexemes processed by your
> "english" config. So, it will have something like:
> ... databas: 123, 129, 200 ...
> Of course, when you do a tsquery search with "simple" configuration it
> checks doesn't do any stemming so is actually looking for a lexeme
> called "database" which it can't find.
>
> Since it can't find anything, it falls back to displaying just the start
> of the document. Since the alternative would be to display nothing, that
> makes a certain amount of sense.
>
> To check this, try: ts_headline(t, to_tsquery('simple','databas')) and
> you should get your database results.
>
>
> Moral of the story: if you specify a configuration, always specify it.
>
> Thanks for working through this Stephen - good question specification btw.

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