| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
| Cc: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Reviewing freeze map code |
| Date: | 2016-06-30 03:43:17 |
| Message-ID: | 20160630034317.r7axkleum65u6t2l@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
On 2016-06-30 08:59:16 +0530, Amit Kapila wrote:
> On Wed, Jun 29, 2016 at 10:30 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On 2016-06-29 19:04:31 +0530, Amit Kapila wrote:
> >> There is nothing in this record which recorded the information about
> >> visibility clear flag.
> >
> > I think we can actually defer the clearing to the lock release?
>
> How about the case if after we release the lock on page, the heap page
> gets flushed, but not vm and then server crashes?
In the released branches there's no need to clear all visible at that
point. Note how heap_lock_tuple doesn't clear it at all. So we should be
fine there, and that's the part where reusing an existing record is
important (for compatibility).
But your question made me realize that we despearately *do* need to
clear the frozen bit in heap_lock_tuple in 9.6...
Greetings,
Andres Freund
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