Thread: Re: [COMMITTERS] pgsql: Prevent "snapshot too old" from trying to return pruned TOAST tu
Re: [COMMITTERS] pgsql: Prevent "snapshot too old" from trying to return pruned TOAST tu
From
Robert Haas
Date:
On Thu, Aug 4, 2016 at 10:58 PM, Robert Haas <robertmhaas@gmail.com> wrote: > On Thu, Aug 4, 2016 at 7:23 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote: >> Robert Haas <rhaas@postgresql.org> writes: >>> Prevent "snapshot too old" from trying to return pruned TOAST tuples. >> >> Looks like this patch broke the build on castoroides. Recommend >> changing InitToastSnapshot into a macro. (There's a reason why >> InitDirtySnapshot is a macro.) > > What is the reason? We refuse to separate frontend and backend > headers in any sort of principled way? That was poorly phrased. I'll try again: I can't see any reason for using a macro here except that it allows frontend code to compile this without breaking. But that doesn't seem like a very good way of solving that problem. There's surely no way for a casual reader of the code to realize that macros can be used here and inline functions cannot, especially because this works apparently works fine on most machines, including mine. Here's a patch. Is this what you want? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
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Re: Re: [COMMITTERS] pgsql: Prevent "snapshot too old" from trying to return pruned TOAST tu
From
Tom Lane
Date:
Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, Aug 4, 2016 at 10:58 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> What is the reason? We refuse to separate frontend and backend
>> headers in any sort of principled way?
> That was poorly phrased. I'll try again: I can't see any reason for
> using a macro here except that it allows frontend code to compile this
> without breaking.
Well, the alternative would be to put "#ifndef FRONTEND" around the
static-inline function. That's not very pretty either, and it's
inconsistent with the existing precedent (ie, InitDirtySnapshot).
Also, it presumes that a non-backend includer actually has defined
FRONTEND; that seems to be the case for pg_xlogdump but I do not
think we do that everywhere.
> Here's a patch. Is this what you want?
OK by me.
regards, tom lane
Re: Re: [COMMITTERS] pgsql: Prevent "snapshot too old" from trying to return pruned TOAST tu
From
Robert Haas
Date:
On Fri, Aug 5, 2016 at 11:05 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Robert Haas <robertmhaas@gmail.com> writes: >> On Thu, Aug 4, 2016 at 10:58 PM, Robert Haas <robertmhaas@gmail.com> wrote: >>> What is the reason? We refuse to separate frontend and backend >>> headers in any sort of principled way? > >> That was poorly phrased. I'll try again: I can't see any reason for >> using a macro here except that it allows frontend code to compile this >> without breaking. > > Well, the alternative would be to put "#ifndef FRONTEND" around the > static-inline function. That's not very pretty either, and it's > inconsistent with the existing precedent (ie, InitDirtySnapshot). > Also, it presumes that a non-backend includer actually has defined > FRONTEND; that seems to be the case for pg_xlogdump but I do not > think we do that everywhere. That may not be pretty, but it'd be a lot more transparent. If I see #ifndef FRONTEND, I think, oh, that's protecting some stuff that shouldn't be included in front-end compiles. If I see a macro, I not necessarily think of the fact that this may be a way of preventing that code from being compiled in front-end compiles. >> Here's a patch. Is this what you want? > > OK by me. OK, committed. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company