On Fri, Mar 24, 2006 at 02:58:54PM +0800, Christopher Kings-Lynne wrote:
Yeah. AFAICS the transformation Chris suggested is valid. I'm really
dubious that it's worth expending planner cycles to look for it though.
LIKE is something that everybody and his brother uses, but who uses this
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.
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
Thomas Hallgren wrote:
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
Tim Allen [EMAIL PROTECTED] writes:
Thomas Hallgren wrote:
The position function must look for 'ch' everywhere in the string so
there's no way it can use an index.
I think the '= 0' bit is what Chris was suggesting could be the basis
for an optimisation.
Yeah. AFAICS the transformation
Tom Lane wrote:
Tim Allen [EMAIL PROTECTED] writes:
Thomas Hallgren wrote:
The position function must look for 'ch' everywhere in the string so
there's no way it can use an index.
I think the '= 0' bit is what Chris was suggesting could be the basis
for an optimisation.
Yeah. AFAICS the transformation Chris suggested is valid. I'm really
dubious that it's worth expending planner cycles to look for it though.
LIKE is something that everybody and his brother uses, but who uses this
position()=0 locution?
One of our junior developers :) Which is why I noticed
Thomas Hallgren wrote:
Tom Lane wrote:
Tim Allen [EMAIL PROTECTED] writes:
Thomas Hallgren wrote:
The position function must look for 'ch' everywhere in the string so
there's no way it can use an index.
I think the '= 0' bit is what Chris was suggesting could be the basis
The docs are correct so my initial point was correct. position('ch' in
user) = 0 is equivalent to user NOT LIKE '%ch%' and there's no way
you can index that.
Well = 1 then.
Chris
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