Re: Partial match in GIN

Alvaro Herrera wrote:
> Heikki Linnakangas wrote:
>> Teodor Sigaev wrote:
>
>>> GIN speeds up '%foo%' too - which is impossible for btree. But I don't
>>> like a hack around LIKE support in BTree. This support uses outflank
>>> ways missing regular one.
>> You could satisfy '%foo%' using a regular and a reverse B-tree index,
>> and a bitmap AND. Which is interestingly similar to the way you proposed
>> to use a TIDBitmap within GIN.
>
> Huh, can you?  I can see doing "col LIKE 'foo%' OR reverse(col) LIKE
> reverse('%foo')" with two btree indexes, but not a true %foo% ...

That should be AND, not OR..

Hmm. It is the same as far as I can see. Am I missing something?

You couldn't support more complex patterns directly, like 'foo%bar%foo',
but you could still split that into 'foo%' AND '%bar%' AND '%foo', and
recheck the matches against the original pattern

--
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com