From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Julien Rouhaud <julien.rouhaud@dalibo.com>,
        pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: segfault in HEAD when too many nested functions call
In-reply-to: <20170724161954.gbqswhukk7c4lygt@alap3.anarazel.de>
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Mon, 24 Jul 2017 09:19:54 -0700"
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Date: Mon, 24 Jul 2017 13:27:58 -0400
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Andres Freund <andres@anarazel.de> writes:
> On 2017-07-21 20:17:54 -0400, Tom Lane wrote:
>>> I dislike having the miscadmin.h include in executor.h - but I don't
>>> quite see a better alternative.

>> I seriously, seriously, seriously dislike that.  You practically might as
>> well put miscadmin.h into postgres.h.  Instead, what do you think of
>> requiring the individual ExecProcNode functions to perform
>> CHECK_FOR_INTERRUPTS?  Since they're already responsible for doing that
>> if they have any long-running internal loops, this doesn't seem like a
>> modularity violation.  It is a risk for bugs-of-omission, sure, but so
>> are a lot of other things that the per-node code has to do.

> That'd work. Another alternative would be to move the inline definition
> of ExecProcNode() (and probably a bunch of other related functions) into
> a more internals oriented header. It seems likely that we're going to
> add more inline functions to the executor, and that'd reduce the
> coupling of external and internal users a bit.

Well, it still ends up that the callers of ExecProcNode need to include
miscadmin.h, whereas if we move it into the per-node functions, then the
per-node files need to include miscadmin.h.  I think the latter is better
because those files may need to have other CHECK_FOR_INTERRUPTS calls
anyway.  It's less clear from a modularity standpoint that executor
callers should need miscadmin.h.  (Or in short, I'm not really okay
with *any* header file including miscadmin.h.)

>> * I think the comments need more work.  Am willing to make a pass over
>> that if you want.

> That'd be good, but let's wait till we have something more final.

Agreed, I'll wait till you produce another version.

>> * Can we redefine the ExecCustomScan function pointer as type
>> ExecProcNodeCB, eliminating the unsightly cast in nodeCustom.c?

> That'd change an "extension API", which is why I skipped it at this
> point of the release cycle. It's not like we didn't have this type of
> cast all over before. Ok, with changing it, but that's where I came
> down.

Is this patch really not changing anything else that a custom-scan
extension would touch?  If not, I'm okay with postponing this bit
of cleanup to v11.

			regards, tom lane


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