Re: [SQLObject] PostgreSQL: costly count

[Ian B. <ia...@co...>]

On Dec 4, 2003, at 9:10 AM, Frank Barknecht wrote:
> Hallo,
>
> getting at the lenght of a result with SQLResult's count() finction
> issues a "select count(*) from X". In my PostgreSQL table, this is
> quite expensive, and I am wondering, why. Analyzing the query shows,
> that no index is used:

> => explain SELECT count(*) from normal;
> NOTICE:  QUERY PLAN:

I don't think an index could be used in this instance.  You aren't 
finding specific rows, you are finding how many total rows there are.

It's kind of dumb that PostgreSQL can't figure this out more quickly, 
since it must have internal records of the table's size already 
calculated.  I know MySQL has specific optimizations for this case 
("SELECT count(*) FROM blah").  If you figure something out, be sure to 
get back to us, maybe there's something that can be added to SQLObject 
to fix this.

--
Ian Bicking | ia...@co... | http://blog.ianbicking.org