Strange result searching with to_tsquery under Postgresql - postgresql

Question

I got a strange result searching for an expression like pro-physik.de with tsquery.
If I ask for pro-physik:* by tsquery I want to get all entries starting with pro-physik. Unfortunately those entries with pro-physik.de are missing.
Here are 2 examples to demonstrate the problem:
Query 1:
select
to_tsvector('simple', 'pro-physik.de') ##
to_tsquery('simple', 'pro-physik:*') = true
Result 1: false (should be true)
Query 2:
select
to_tsvector('simple', 'pro-physik.de') ##
to_tsquery('simple', 'pro-p:*') = true
Result 2: true
Has anybody an idea how I could solve this problem?

Answer 1

The core of the problem is that the parser will parse pro-physik.de as a hostname:
SELECT alias, token FROM ts_debug('simple', 'pro-physik.de');
alias | token
-------+---------------
host | pro-physik.de
(1 row)
Compare this:
SELECT alias, token FROM ts_debug('simple', 'pro-physik-de');
alias | token
-----------------+---------------
asciihword | pro-physik-de
hword_asciipart | pro
blank | -
hword_asciipart | physik
blank | -
hword_asciipart | de
(6 rows)
Now pro-physik and pro-p are not hostnames, so you get
SELECT to_tsquery('simple', 'pro-physik:*');
to_tsquery
---------------------------------------
'pro-physik':* & 'pro':* & 'physik':*
(1 row)
SELECT to_tsquery('simple', 'pro-p:*');
to_tsquery
-----------------------------
'pro-p':* & 'pro':* & 'p':*
(1 row)
The first tsquery will not match because physik is not a prefix of pro-physik.de, and the second will match because pro-p, pre and p all three are prefixes.
As a workaround, use full text search like this:
select
to_tsvector('simple', replace('pro-physik.de', '.', ' ')) ##
to_tsquery('simple', replace('pro-physik:*', '.', ' '))