On Wed, Jun 20, 2012 at 1:39 PM, Alan Hodgson <ahodgson@simkin.ca> wrote:
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.