Re: PATCH: Batch/pipelining support for libpq

From: Vaishnavi Prabakaran <vaishnaviprabakaran(at)gmail(dot)com>
To: Daniel Verite <daniel(at)manitou-mail(dot)org>
Cc: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, "Prabakaran, Vaishnavi" <VaishnaviP(at)fast(dot)au(dot)fujitsu(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>, Dmitry Igrishin <dmitigr(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Manuel Kniep <m(dot)kniep(at)web(dot)de>, "fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp" <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>, "Iwata, Aya" <iwata(dot)aya(at)jp(dot)fujitsu(dot)com>
Subject: Re: PATCH: Batch/pipelining support for libpq
Date: 2017-03-16 02:42:33
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On Tue, Mar 14, 2017 at 5:50 PM, Vaishnavi Prabakaran <
vaishnaviprabakaran(at)gmail(dot)com> wrote:

> On Tue, Mar 14, 2017 at 4:19 AM, Daniel Verite <daniel(at)manitou-mail(dot)org>
> wrote:
>> I mean the next iteration of the above while statement. Referring
>> to the doc, that would be the "next batch entry":
>> " To get the result of the first batch entry the client must call
>> PQbatchQueueProcess. It must then call PQgetResult and handle the
>> results until PQgetResult returns null (or would return null if
>> called). The result from the next batch entry may then be retrieved
>> using PQbatchQueueProcess and the cycle repeated"
>> Attached is a bare-bones testcase showing the problem.
>> As it is, it works, retrieving results for three "SELECT 1"
>> in the same batch. Now in order to use the single-row
>> fetch mode, consider adding this:
>> r = PQsetSingleRowMode(conn);
>> if (r!=1) {
>> fprintf(stderr, "PQsetSingleRowMode() failed for i=%d\n", i);
>> }
>> When inserted after the call to PQbatchQueueProcess,
>> which is what I understand you're saying works for you,
>> it fails for me when starting to get the results of the 2nd query
>> and after.
> Thanks for explaining the issue in detail and yes, I do see the issue
> using your attached test file.
> And I think the problem is with the "parseInput" call at the end of
> PQbatchQueueProcess().
> I don't see the need for "parseInput" to cover the scope of
> PQbatchQueueProcess(), also anyways we do it in PQgetResult().
> This function call changes the asyncstatus of connection to
> READY(following command complete message from backend), so eventually
> PQsetSingleRowMode() is failing. So, attached the alternative fix for this
> issue.
Please share me your thoughts.
> I would also like to hear Craig's opinion on it before applying this fix
> to the original patch, just to make sure am not missing anything here.
Attached the code patch applied with the fix explained above and moving the
CF status seeking review.

Thanks & Regards,
Fujitsu Australia.

Attachment Content-Type Size
0001-Pipelining-batch-support-for-libpq-code-v6.patch application/octet-stream 49.5 KB
0002-Pipelining-batch-support-for-libpq-test-v3.patch application/octet-stream 43.4 KB

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