Re: efficiency of wildcards at both ends

On Wednesday, June 20, 2012 01:10:03 PM Sam Z J wrote:
> Hi all
>
> I'm curious how is wildcards at both ends implemented, e.g. LIKE '%str%'
> How efficient is it if that's the only search criteria against a large
> table? how much does indexing the column help and roughly how much more
> space is needed for the index?
>

Indexing helps not at all. If the search string starts with a wildcard you
will always get a sequential scan of the whole table.

Look at the full text search documentation for a better approach.