Christopher Kings-Lynne wrote:
Is it worth allowing this:
select count(*) from users_users where position('ch' in username) = 0;
To be able to use an index, like:
select count(*) from users_users where username like 'ch%';
At the moment the position() syntax will do a seqscan, but the like
syntax will use an index.
You must compare position('ch' in username) to '%ch%' instead of 'ch%' in this
respect.
The position function must look for 'ch' everywhere in the string so there's no way it can
use an index.
Regards,
Thomas Hallgren
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TIP 6: explain analyze is your friend
