Re: [HACKERS] advanced partition matching algorithm for partition-wise join

Hi Amul,

On Fri, Oct 25, 2019 at 6:59 PM amul sul <sulamul@gmail.com> wrote:
> On Wed, Oct 16, 2019 at 6:20 PM Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
>> So I'd like to propose to introduce separate functions like
>> process_outer_partition() and process_inner_partition() in the
>> attached, instead of handle_missing_partition().  (I added a fast path
>> to these functions that if both outer/inner sides have the default
>> partitions, give up on merging partitions.  Also, I modified the
>> caller sites of proposed functions so that they call these if
>> necessary.)

> Agree -- process_outer_partition() & process_inner_partition() approach looks
> much cleaner than before.
>
> Here are the few comments:

Thanks for the review!

> Note that LHS numbers are the line numbers in your previously posted patch[1].
>
>  455 +               if (inner_has_default ||
>  456 +                   jointype == JOIN_LEFT ||
>  457 +                   jointype == JOIN_ANTI ||
>  458 +                   jointype == JOIN_FULL)
>  459 +               {
>  460 +                   if (!process_outer_partition(&outer_map,
>
>  512 +               if (outer_has_default || jointype == JOIN_FULL)
>  513 +               {
>  514 +                   if (!process_inner_partition(&outer_map,
>
> How about adding these conditions to the else block of process_outer_partition()
> & process_inner_partition() function respectively so that these functions can be
> called unconditionally?  Thoughts/Comments?

I'm not sure that's a good idea; these functions might be called many
times, so I just thought it would be better to call these functions
conditionally, to avoid useless function call overhead.

>  456 +                   jointype == JOIN_LEFT ||
>  457 +                   jointype == JOIN_ANTI ||
>  458 +                   jointype == JOIN_FULL)
>
> Also, how about using IS_OUTER_JOIN() instead. But we need an assertion to
> restrict JOIN_RIGHT or something.

Seems like a good idea.

> For the convenience, I did both aforesaid changes in the attached delta patch that
> can be applied atop of your previously posted patch[1].  Kindly have a look & share
> your thoughts, thanks.

Thanks for the patch!

> 1273 + * *next_index is incremented when creating a new merged partition associated
> 1274 + * with the given outer partition.
> 1275 + */
>
> Correction: s/outer/inner
> ---
>
> 1338 +        * In range partitioning, if the given outer partition is already
> 1339 +        * merged (eg, because we found an overlapping range earlier), we know
> 1340 +        * where it fits in the join result; nothing to do in that case.  Else
> 1341 +        * create a new merged partition.
>
> Correction: s/outer/inner.
> ---
>
> 1712         /*
> 1713          * If the NULL partition was missing from the inner side of the join,
>
> s/inner side/outer side
> --

Good catch!  Will fix.

Best regards,
Etsuro Fujita