> I want to do a regex match limited to words.
>
> I tried this:
>
> where ... ~ '\Wword\W';
> where ... ~ '\W*word\W*';
> where ... ~ '\b\(word\)\b';
>
> and other things with LIKE but no joy.
Based on the comments in the source, regexp stuff used in postgres is something like this:
http://tiger8.com/us/regexp-manpage.html
I guess there are no backslash macros is POSIX expressions. No joy. By the way, I am wondering what determined the
choiceof the regexp machine for postgres? Is it performance-related? Is it possible to have the same stuff as in perl?
As to your question, how about a poor man's Altavista like this:
Split the text into words before loading into a special index table. Words are numbered sequentially, so you can search
for"phrases":
Table = word
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| rec | char() | 12 |
| seq | int4 | 4 |
| word | text | var |
+----------------------------------+----------------------------------+-------+
SELECT DISTINCT w1.rec
FROM word w1, word w2
WHERE
w1.word ~ '^a$'
AND w2.word ~ '^phrase$'
AND w1.rec = w2.rec
AND w2.seq - w1.seq = 1; -- Distance between the words
This way, you can control what represents the concept of a 'word' by an external program (perl script, etc.)
Certainly, this method will show suboptimal performance with extra large tables and more than three or four words in a
seachphrase. But it is possible to optimise by delegating set operations (joins) and position arithmetic to the client.
Itworks very well for my ~500k tables and the most common queries.
--Gene
