It looks like there is a very old bug in full text parser (somebody
pointed me on it), which appeared after moving tsearch2 into the core. The
problem is in how full text parser process hyphenated words. Our original
idea was to report hyphenated word itself as well as its parts and ignore
hyphen. That was how tsearch2 works.
This behaviour was changed after moving tsearch2 into the core:
1. hyphen now reported by parser, which is useless.
2. Hyphenated words with numbers ('4-dot', 'dot-4') processed differently
than ones with plain text words like 'four-dot', no hyphenated word itself
reported.
I think we should consider this as a bug and produce fix for all supported
versions.
After investigation we found this commit:
commit 73e6f9d3b61995525785b2f4490b465fe860196b
Author: Tom Lane <t...@sss.pgh.pa.us>
Date: Sat Oct 27 19:03:45 2007 +0000
Change text search parsing rules for hyphenated words so that digit
strings
containing decimal points aren't considered part of a hyphenated word.
Sync the hyphenated-word lookahead states with the subsequent
part-by-part
reparsing states so that we don't get different answers about how much
text
is part of the hyphenated word. Per my gripe of a few days ago.
8.2.23
select tok_type, description, token from ts_debug('dot-four');
tok_type | description | token
-------------+-------------------------------+----------
lhword | Latin hyphenated word | dot-four
lpart_hword | Latin part of hyphenated word | dot
lpart_hword | Latin part of hyphenated word | four
(3 rows)
select tok_type, description, token from ts_debug('dot-4');
tok_type | description | token
-------------+-------------------------------+-------
hword | Hyphenated word | dot-4
lpart_hword | Latin part of hyphenated word | dot
uint | Unsigned integer | 4
(3 rows)
select tok_type, description, token from ts_debug('4-dot');
tok_type | description | token
----------+------------------+-------
uint | Unsigned integer | 4
lword | Latin word | dot
(2 rows)
8.3.23
select alias, description, token from ts_debug('dot-four');
alias | description | token
-----------------+---------------------------------+----------
asciihword | Hyphenated word, all ASCII | dot-four
hword_asciipart | Hyphenated word part, all ASCII | dot
blank | Space symbols | -
hword_asciipart | Hyphenated word part, all ASCII | four
(4 rows)
select alias, description, token from ts_debug('dot-4');
alias | description | token
-----------+-----------------+-------
asciiword | Word, all ASCII | dot
int | Signed integer | -4
(2 rows)
select alias, description, token from ts_debug('4-dot');
alias | description | token
-----------+------------------+-------
uint | Unsigned integer | 4
blank | Space symbols | -
asciiword | Word, all ASCII | dot
(3 rows)
Regards,
Oleg
