| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Kevin Grittner <kgrittn(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Steve Singer <steve(at)ssinger(dot)info>, Kevin Grittner <kgrittn(at)ymail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: snapshot too old, configured by time |
| Date: | 2016-03-30 20:26:23 |
| Message-ID: | 20160330202623.GA2882@alvherre.pgsql |
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| Lists: | pgsql-hackers |
Kevin Grittner wrote:
> On Wed, Mar 30, 2016 at 2:22 PM, Alvaro Herrera
> <alvherre(at)2ndquadrant(dot)com> wrote:
> > I said that we should change BufferGetPage into having the snapshot
> > check built-in, except in the cases where a flag is passed; and the flag
> > would be passed in all cases except those 30-something you identified.
> > In other words, the behavior in all the current callsites would be
> > identical to what's there today; we could have a macro do the first
> > check so that we don't introduce the overhead of a function call in the
> > 450 cases where it's not needed.
>
> In many of the places that BufferGetPage is called there is not a
> snapshot available. I assume that you would be OK with an Assert
> that the flag was passed if the snapshot is NULL?
Sure, that's fine.
BTW I said "a macro" but I was forgetting that we have static inline
functions in headers now, which means you can avoid the horrors of
actually writing a macro.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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