| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Kevin Grittner <kgrittn(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 16:37:32 |
| Message-ID: | 18814.1459355852@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> I think a safer proposition would be to replace all current
> BufferGetPage() calls (there are about 500) by adding the necessary
> arguments: buffer, snapshot, rel, and an integer "flags". All this
> without adding the feature. Then a subsequent commit would add the
> TestForOldSnapshot inside BufferGetPage, *except* when a
> BUFFER_NO_SNAPSHOT_TEST flag is passed. That way, new code always get
> the snapshot test by default.
That seems awfully invasive, not to mention performance-killing if
the expectation is that most such calls are going to need a snapshot
check. (Quite aside from the calls themselves, are they all in
routines that are being passed the right snapshot today?)
TBH, I think that shoving in something like this at the end of the last
commitfest would be a bad idea even if there were widespread consensus
that we wanted the feature ... which I am not sure there is.
I think it might be time to bounce this one to 9.7.
regards, tom lane
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