Another thing I noticed: if you test with tsvectors that don't contain
position info, <-> seems to reduce to &, that is it doesn't enforce
relative position:
regression=# select 'cat bat fat rat'::tsvector @@ 'cat <-> rat'::tsquery;?column?
----------t
(1 row)
regression=# select 'rat cat bat fat'::tsvector @@ 'cat <-> rat'::tsquery;?column?
----------t
(1 row)
I'm doubtful that this is a good behavior, because it seems like it can
silently mask mistakes. That is, applying <-> to a stripped tsvector
seems like user error to me. Actually throwing an error might be too
much, but perhaps we should make such cases return false not true?
(This is against HEAD, without the patch I suggested yesterday.
It strikes me that that patch might change this behavior, if the
lexemes are all being treated as having position zero, but I have
not checked.)
regards, tom lane