[Dbix-class] coercing Result objects
lenjaffe at jaffesystems.com
Mon Nov 26 17:19:24 GMT 2012
On Mon, Nov 26, 2012 at 11:38 AM, Ben Tilly <btilly at gmail.com> wrote:
> Random tip in case you don't know it. A union has an implicit dedupe
> in it, which is quite expensive. If ou can, you really want to make
> that a UNION ALL instead.
> (Database people all know this, developers generally don't.)
Expensive bacause dedupe is typically implemented using either a sort, or
the building of a hash table. Both are order N (or worse) operations.
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