Re: left join with smaller table or index on (XXX is not null) to avoid upsert

On Mon, Jan 19, 2009 at 12:12 AM, Grzegorz Jaśkiewicz <gryzman(at)gmail(dot)com> wrote:
> On Mon, Jan 19, 2009 at 2:44 AM, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> wrote:
>> Watch out for bloat when doing this. A simple where change of
>>
>> update table set b = 45 ;
>>
>> to
>>
>> update table set b = 45 where b <> 45 ;
>>
>> can save the db a lot of work, and if you can apply the same logic to
>> your update to save some dead tuples it's worth looking into.
>
> I wonder why DB can't do it on its own :)

Submit a patch. :)

But seriously, it's doing what you told it to do. There might be
corner cases where you need a trigger to fire for a row on change, and
short-circuiting could cause things to fail in unexpected ways.