Re: Reviewing freeze map code

On Thu, Jun 30, 2016 at 3:12 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Thu, Jun 30, 2016 at 9:13 AM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> 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).
>>
>
> For back branches, I agree that heap_lock_tuple is sufficient,

Even if we use heap_lock_tuple, If server crashed after flushed heap
but not vm, after crash recovery the heap is still marked all-visible
on vm.
This case could be happen even on released branched, and could make
IndexOnlyScan returns wrong result?

Regards,

--
Masahiko Sawada