Re: Mailing list search engine: surprising missing results?

Ivan Panchenko <i(dot)panchenko(at)postgrespro(dot)ru> writes:
> The actual explanation can be seen from comparing a tsvector with a tsquery.
> To avoid stemming effects, we use the simple configuration below.

> # select plainto_tsquery('simple','boyers-moore');

>            plainto_tsquery
> -------------------------------------
>  'boyers-moore' & 'boyers' & 'moore'

> # select to_tsvector('simple','boyers-moore-horspool');

>                          to_tsvector
> -------------------------------------------------------------
>  'boyers':2 'boyers-moore-horspool':1 'horspool':4 'moore':3

> Obviously, such tsvector does not match the above tsquery. I think,a better tsquery for this query would be

>  'boyers-moore' | ('boyers' & 'moore')

> May be, it is worth changing to_tsquery() behavior for such cases.

Changing the behavior of to_tsquery is certainly a lot less scary
than changing to_tsvector --- it wouldn't call the validity of
existing tsvector indexes into question.

I see that to_tsquery is even sillier than plainto_tsquery:

regression=# select to_tsquery('simple','boyers-moore');
to_tsquery
-----------------------------------------
'boyers-moore' <-> 'boyers' <-> 'moore'
(1 row)

which is absolutely not a sane translation.

It seems to me that in both cases we'd be better off generating
"'boyers' <-> 'moore'", without the compound token at all.
Maybe there's a case for the weaker 'boyers' & 'moore' translation,
but I think if people wanted that they'd just enter separate words.

regards, tom lane