| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Simon Riggs <simon(at)2ndquadrant(dot)com>, alvherre(at)commandprompt(dot)com, david(at)fetter(dot)org, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Page Checksums + Double Writes |
| Date: | 2011-12-23 20:25:57 |
| Message-ID: | 1547.1324671957@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Jeff Janes <jeff(dot)janes(at)gmail(dot)com> writes:
> I had a perhaps crazier idea. Aren't CLOG pages older than global xmin
> effectively read only? Could backends that need these bypass locking
> and shared memory altogether?
Hmm ... once they've been written out from the SLRU arena, yes. In fact
you don't need to go back as far as global xmin --- *any* valid xmin is
a sufficient boundary point. The only real problem is to know whether
the data's been written out from the shared area yet.
This idea has potential. I like it better than Robert's, mainly because
I do not want to see us put something in place that would lead people to
try to avoid rollbacks.
regards, tom lane
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