Re: Reviewing freeze map code

On Sat, Jul 2, 2016 at 12:17 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Sat, Jul 2, 2016 at 12:53 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> On 2016-07-01 15:18:39 -0400, Robert Haas wrote:
>>> On Fri, Jul 1, 2016 at 10:22 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>>> > Ah, you're right, I misunderstood.
>>> >
>>> > Attached updated patch incorporating your comments.
>>> > I've changed it so that heap_xlog_lock clears vm flags if page is
>>> > marked all frozen.
>>>
>>> I believe that this should be separated into two patches, since there
>>> are two issues here:
>>>
>>> 1. Locking a tuple doesn't clear the all-frozen bit, but needs to do so.
>>> 2. heap_update releases the buffer content lock without logging the
>>> changes it has made.
>>>
>>> With respect to #1, there is no need to clear the all-visible bit,
>>> only the all-frozen bit. However, that's a bit tricky given that we
>>> removed PD_ALL_FROZEN. Should we think about putting that back again?
>>
>> I think it's fine to just do the vm lookup.
>>
>>> Should we just clear all-visible and call it good enough?
>>
>> Given that we need to do that in heap_lock_tuple, which entirely
>> preserves all-visible (but shouldn't preserve all-frozen), ISTM we
>> better find something that doesn't invalidate all-visible.
>>
>
> Sounds logical, considering that we have a way to set all-frozen and
> vacuum does that as well. So probably either we need to have a new
> API or add a new parameter to visibilitymap_clear() to indicate the
> same. If we want to go that route, isn't it better to have
> PD_ALL_FROZEN as well?
>

Cant' we call visibilitymap_set with all-visible but not all-frozen
bits instead of clearing flags?

Regards,

--
Masahiko Sawada