From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, "Adam, Etienne (Nokia-TECH/Issy Les Moulineaux)" <etienne(dot)adam(at)nokia(dot)com>, PostgreSQL Bugs <pgsql-bugs(at)postgresql(dot)org>, "Duquesne, Pierre (Nokia-TECH/Issy Les Moulineaux)" <pierre(dot)duquesne(at)nokia(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: [HACKERS] [postgresql 10 beta3] unrecognized node type: 90 |
Date: | 2017-08-17 09:55:45 |
Message-ID: | CAA4eK1JkByysFJNh9M349u_nNjqETuEnY_y1VUc_kJiU0bxtaQ@mail.gmail.com |
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Lists: | pgsql-bugs pgsql-hackers |
On Thu, Aug 17, 2017 at 10:07 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Tue, Aug 15, 2017 at 7:16 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>
>>> I believe that between this commit and the test-coverage commit from
>>> Andres, this open item is reasonably well addressed. If someone
>>> thinks more needs to be done, please specify. Thanks.
>>
>> How big a deal do we think test coverage is? It looks like
>> ExecReScanGatherMerge is identical logic to ExecReScanGather,
>> which *is* covered according to coverage.postgresql.org, but
>> it wouldn't be too surprising if they diverge in future.
>>
>> I should think it wouldn't be that expensive to create a test
>> case, if you already have test cases that invoke GatherMerge.
>> Adding a right join against a VALUES clause with a small number of
>> entries, and a non-mergeable/hashable join clause, ought to do it.
>>
>
>
> Another way to make it parallel is, add a new guc enable_gather
> similar to enable_gathermerge and then set that to off, it will prefer
> GatherMerge in that case. I think it is anyway good to have such a
> guc. I will go and do it this way unless you have a better idea.
>
Going by above, I have created two separate patches. First to
introduce a new guc enable_gather and second patch to test the rescan
behavior of gather merge. I have found a problem in the rescan path
of gather merge which is that it is not initializing the gather merge
state which is required to initialize the heap for processing of
tuples. I think this should have been caught earlier, but probably I
didn't notice it because in the previous tests left side would not
have passed enough rows to hit this case. I have fixed it in the
attached patch (execrescan_gathermerge_v2).
> Note - enable_gathermerge is not present in postgresql.conf. I think
> we should add it in the postgresql.conf.sample file.
>
Thomas has already posted a patch to handle this problem.
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
Attachment | Content-Type | Size |
---|---|---|
guc_enable_gather_v1.patch | application/octet-stream | 3.0 KB |
execrescan_gathermerge_v2.patch | application/octet-stream | 3.4 KB |
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