Horton

Re: Asynchronous Append on postgres_fdw nodes.

movead.li@highgo.ca <movead.li@highgo.ca>

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From: "movead.li@highgo.ca" <movead.li@highgo.ca>
To: "Etsuro Fujita" <etsuro.fujita@gmail.com>, Horiguchi <horikyota.ntt@gmail.com>
Cc: "Justin Pryzby" <pryzby@telsasoft.com>, "Andrey V. Lepikhov" <a.lepikhov@postgrespro.ru>, "Ahsan Hadi" <ahsan.hadi@gmail.com>, pgsql-hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-11-26T01:28:06Z
Lists: pgsql-hackers 
I test the patch and occur several issues as blow:

Issue one:
Get a Assert error at 'Assert(bms_is_member(i, node->as_needrequest));' in
ExecAppendAsyncRequest() function when I use more than two foreign table
on different foreign server.

I research the code and do such change then the Assert problom disappear.

@@ -1004,6 +1004,7 @@ ExecAppendAsyncResponse(AsyncRequest *areq) bms_del_member(node->as_needrequest, areq->request_index); node->as_asyncpending = bms_add_member(node->as_asyncpending, areq->request_index); + node->as_lastasyncplan = INVALID_SUBPLAN_INDEX; return false; }

Issue two:
Then I test and find if I have sync subplan and async sunbplan, it will run over
the sync subplan then the async turn, I do not know if it is intent.

Issue three:
After code change mentioned in the Issue one, I can not get performance improvement.
I query on partitioned table and all sub-partition the time spent on partitioned table
always same as the sum of all sub-partition.

Sorry if I have something wrong when test the patch.



Regards,
Highgo Software (Canada/China/Pakistan) 
URL : www.highgo.ca

Commits

  1. Improve comments for trivial_subqueryscan().

  2. Disable asynchronous execution if using gating Result nodes.

  3. Allow asynchronous execution in more cases.

  4. Doc: Further update documentation for asynchronous execution.

  5. Fix rescanning of async-aware Append nodes.

  6. Doc: Update documentation for asynchronous execution.

  7. Fix EXPLAIN ANALYZE for async-capable nodes.

  8. Minor code cleanup in asynchronous execution support.

  9. Adjust input value to WaitEventSetWait() in ExecAppendAsyncEventWait().

  10. Add support for asynchronous execution.