From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, Noah Misch <noah(at)leadboat(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Suspicious behaviour on applying XLOG_HEAP2_VISIBLE. |
Date: | 2016-04-15 17:12:07 |
Message-ID: | 22798.1460740327@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Apr 14, 2016 at 12:11 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> The easiest way to achieve that seems to be to just assign an xid if
>> that's the case; while it's not necessarily safe/efficient to do so at
>> the point the invalidation message was queued, I think it should be safe
>> to do so at commit time. Seems less invasive to backpatch than to either
>> support commit records without xids, or a separate record just
>> transporting invalidation messages.
> I agree that's better for back-patching. I hope it won't suck
> performance-wise. In master, we might think of inventing something
> new.
I'm a little worried about whether this will break assumptions that
vacuum doesn't have an XID. I don't immediately see how it would,
but it seems a bit shaky.
I find it hard to believe that the act of assigning an XID would add
measurably to the cost of a vacuum, so Robert's performance concern
doesn't sound very exciting. If this works, I think it's fine to
adopt as a permanent solution.
regards, tom lane
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