On 5/10/16 12:47 AM, Kouhei Kaigai wrote:
>> > On 10 May 2016 at 13:38, Kouhei Kaigai <kaigai@ak.jp.nec.com> wrote:
>>> > > My concern about ExecProcNode is, it is constructed with a large switch
>>> > > ... case statement. It involves tons of comparison operation at run-time.
>>> > > If we replace this switch ... case by function pointer, probably, it make
>>> > > performance improvement. Especially, OLAP workloads that process large
>>> > > amount of rows.
>> >
>> > I imagined that any decent compiler would have built the code to use
>> > jump tables for this. I have to say that I've never checked to make
>> > sure though.
>> >
> Ah, indeed, you are right. Please forget above part.
Even so, I would think that the simplification in the executor would be
worth it. If you need to add a new node there's dozens of places where
you might have to mess with these giant case statements.
In python (for example), types (equivalent to nodes in this case) have
data structures that define function pointers for a core set of
operations (such as doing garbage collection, or generating a string
representation). That means that to add a new type at the C level you
only need to define a C structure that has the expected members, and an
initializer function that will properly set everything up when you
create a new instance. There's no messing around with the rest of the
guts of python.
*Even more important, everything you need to know about the type is
contained in one place, not spread throughout the code.*
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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