Searching email, Full Text Search prefix, not expected results - Mailing list pgsql-general

Hi guys, I'm going to crazy about FTS with prefix agains email values on tsvector. Follow how to reproduce:

For the next tsvector:

=# select to_tsvector('user@company.com')

     to_tsvector      

----------------------

 'user@company.com':1

I expects TRUE for all next tsqueryes:

select to_tsvector('user@company.com') @@ to_tsquery('u:*');

select to_tsvector('user@company.com') @@ to_tsquery('us:*');

select to_tsvector('user@company.com') @@ to_tsquery('use:*');

select to_tsvector('user@company.com') @@ to_tsquery('user:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@c:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@co:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@com:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@comp:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@compa:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@compan:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@company:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@company.:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@company.c:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@company.co:*');

select to_tsvector('user@company.com') @@ to_tsquery('user@company.com:*');

But NOT, there are some NOT expected and confusing me results:

=# select to_tsvector('user@company.com') @@ to_tsquery('us:*');

 ?column? 

----------

 t

(1 row)

=# select to_tsvector('user@company.com') @@ to_tsquery('user:*');

 ?column? 

----------

 t

=# select to_tsvector('user@company.com') @@ to_tsquery('user@:*');

 ?column? 

----------

 t

select to_tsvector('user@company.com') @@ to_tsquery('user@comp:*');

 ?column? 

----------

 f   <---- FALSE (I expects TRUE)

=# select to_tsvector('user@company.com') @@ to_tsquery('user@company:*');

 ?column? 

----------

 f   <---- FALSE (I expects TRUE)

=# select to_tsvector('user@company.com') @@ to_tsquery('user@company.:*');

 ?column? 

----------

 f   <---- FALSE (I expects TRUE)

=# select to_tsvector('user@company.com') @@ to_tsquery('user@company.c:*');

 ?column? 

----------

 f  <---- FALSE  (I expects TRUE)

=# select to_tsvector('user@company.com') @@ to_tsquery('user@company.co:*');

 ?column? 

----------

 t  <---- TRUE .... OOhhhhhHHH I'm going crazy!!!

=# select to_tsvector('user@company.com') @@ to_tsquery('user@company.com:*');

 ?column? 

----------

 t  <---- TRUE ... Yes I'm crazy.

Please some ligths about it.

(I follow the official docs in http://www.postgresql.org/docs/9.1/interactive/textsearch.html for my knowledge) 

Thx!