Re: Optimization for updating foreign tables in Postgres FDW

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Noah Misch <noah(at)leadboat(dot)com>, Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Optimization for updating foreign tables in Postgres FDW
Date: 2016-04-27 03:16:01
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On 2016/04/26 21:45, Etsuro Fujita wrote:
> While re-reviewing the fix, I noticed that since PQcancel we added to
> pgfdw_xact_callback to cancel a DML pushdown query isn't followed by a
> ROLLBACK, the connection to the remote server will be discarded at the
> end of the while loop in that function, which will cause a FATAL error
> of "connection to client lost". Probably, that was proposed by me in
> the first version of the patch, but I don't think that's a good idea.
> Shouldn't we execute ROLLBACK after that PQcancel?
> Another thing I noticed is, ISTM that we miss the case where DML
> pushdown queries are performed in subtransactions. I think cancellation
> logic would also need to be added to pgfdw_subxact_callback.

Attached is a patch for that.

Best regards,
Etsuro Fujita

Attachment Content-Type Size
pgfdw-xact-subxact-callbacks.patch text/x-diff 2.2 KB

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