Re: Behavior of a pg_trgm index for 2 (or < 3) character LIKE queries

On Fri, May 31, 2013 at 4:25 AM, Alexander Korotkov
<aekorotkov@gmail.com> wrote:
> On Thu, May 30, 2013 at 12:49 PM, Sawada Masahiko <sawada.mshk@gmail.com>
> wrote:
>>
>> following emails are discussed about partial match of pg_trgm.  I hope
>> will this help.
>>
>> <http://www.postgresql.org/message-id/CAHGQGwFJshvV2nGME19wdTW9teFw_w7h2ns4E+YYsjkB9WdWDQ@mail.gmail.com>
>> as you may know, if search string contains multibyte characters
>> trigram key is converted to CRC of 4 byte and it is used as key.
>> (but only use upper 3 byte from CRC)
>> so we can do partial matching if KEEPONLYALNUM is enabled.
>
>
> Please, read the further discussion on that thread. We can't do partial
> matching because of CRC independently of KEEPONLYALNUM.
>

Thank you Sawada-san and Alexander.

I think the idea of using trigram "text" itself rather than its CRC
(due to its problems in partial matching) as GIN key (?) has not been
implemented into pg_trgm yet, right? And even though, such a facility
would  be added, we would still need to handle multibyte characters
case differently (even for partial matching), is that right?



--
Amit Langote