On Tue, Sep 20, 2011 at 3:51 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> This performance patch differs from most in that it's difficult in
>> principle to imagine a performance regression occurring.
>
> Really? N copies of the same code could lead to performance loss just
> due to code bloat (ie, less of a query's inner loops fitting in CPU
> cache). Not to mention the clear regression in maintainability. So
> I'm disinclined to consider this sort of change without a significantly
> bigger win than you're suggesting above (no, I don't even consider the
> -O0 number attractive, let alone what you're finding at -O2).
More copies of the code are somewhat annoying, but its only 100 lines
of code in one module and we can easily have specific tests for each.
The extra code size is minor in comparison to the reams of code we add
elsewhere.
It's a surprisingly good win for such a common use case. Well done, Peter.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
