Re: [DESIGN] ParallelAppend

On Tue, Aug 18, 2015 at 11:27 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>> Here is one other issue I found. Existing code assumes a TOC segment has
>> only one contents per node type, so it uses pre-defined key (like
>> PARALLEL_KEY_SCAN) per node type, however, it is problematic if we put
>> multiple PlannedStmt or PartialSeqScan node on a TOC segment.
>
> We have few keys in parallel-seq-scan patch
> (PARALLEL_KEY_TUPLE_QUEUE and PARALLEL_KEY_INST_INFO) for
> which multiple structures are shared between master and worker backends.
>
> Check if something similar can work for your use case.

I think you are possibly missing the point.  I think KaiGai's correct,
and I pointed out the same problem to you before.  The parallel key
for the Partial Seq Scan needs to be allocated on the fly and carried
in the node, or we'll never be able to push multiple things below the
funnel.  I'm not quite sure what you're trying to explain with this
response.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company