to_tsvector() with hyphens

Hey everyone,

I think it's great that the full text search parser breaks hyphenated words into multiple parts. I think this really could help, but something is not right.

rasmas_hackathon=> select * from ts_debug( 'gn-foo' );
alias | description | token | dictionaries | dictionary | lexemes
-----------------+---------------------------------+---------+----------------+--------------+----------
asciihword | Hyphenated word, all ASCII | gn-foo | {english_stem} | english_stem | {gn-foo}
hword_asciipart | Hyphenated word part, all ASCII | gn | {english_stem} | english_stem | {gn}
blank | Space symbols | - | {} | |
hword_asciipart | Hyphenated word part, all ASCII | foo | {english_stem} | english_stem | {foo}
blank | Space symbols | | {} | |
(6 rows)

But why does to_tsquery() AND them?

rasmas_hackathon=> select * from to_tsquery( 'gn-foo | bandage' );
to_tsquery
------------------------------------
'gn-foo' & 'gn' & 'foo' | 'bandag'
(1 row)

Perhaps my vector is like this:

rasmas_hackathon=> select to_tsvector( 'gn series bandage' );
to_tsvector
-----------------------------
'bandag':3 'gn':1 'seri':2
(1 row)

The rank is so bad.

rasmas_hackathon=> select ts_rank_cd( to_tsvector( 'gn series bandage' ), to_tsquery( 'gn-foo | bandage' ) );
ts_rank_cd
------------
0.1
(1 row)

Without the hyphen the rank is better, despite the process above.

rasmas_hackathon=> select ts_rank_cd( to_tsvector( 'gn series bandage' ), to_tsquery( 'gn | bandage' ) );
ts_rank_cd
------------
0.2
(1 row)

So wouldn't this be a better query for hyphenated words?

'gn-foo' | 'gn' | 'foo'

Aside: Best i can tell the parser is giving instructions to pushval_morph() to treat hyphenated words as
"same variants".

thanks,
Brian

--
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http://mappingdc.org
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