Re: [HACKERS] Partition-wise join for join between (declaratively)partitioned tables

On Wed, Mar 15, 2017 at 8:49 AM, Ashutosh Bapat
<ashutosh.bapat@enterprisedb.com> wrote:
>> Of course, that supposes that 0009 can manage to postpone creating
>> non-sampled child joinrels until create_partition_join_plan(), which
>> it currently doesn't.
>
> Right. We need the child-join's RelOptInfos to estimate sizes, so that
> we could sample the largest ones. So postponing it looks difficult.

You have a point.

>> In fact, unless I'm missing something, 0009
>> hasn't been even slightly adapted to take advantage of the
>> infrastructure in 0001; it doesn't seem to reset the path_cxt or
>> anything.  That seems like a fairly major omission.
>
> The path_cxt reset introduced by 0001 recycles memory used by all the
> paths, including paths created for the children. But that happens only
> after all the planning has completed. I thought that's what we
> discussed to be done. We could create a separate path context for
> every top-level child-join.

I don't think we need to create a new context for each top-level
child-join, but I think we should create a context to be used across
all top-level child-joins and then reset it after planning each one.
I thought the whole point here was that NOT doing that caused the
memory usage for partitionwise join to get out of control.  Am I
confused?

-- 
Robert Haas
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