Re: COPY FREEZE and PD_ALL_VISIBLE

On Tue, Nov 3, 2015 at 6:37 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On 3 November 2015 at 15:23, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>
>> On Fri, Oct 23, 2015 at 6:29 AM, Simon Riggs <simon(at)2ndquadrant(dot)com>
>> wrote:
>>>
>>> On 21 October 2015 at 13:31, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
>>>
>>>> Index-only scans will visit the heap for each tuple until the first
>>>> VACUUM is done.
>>>>
>>>> The first vacuum will read the entire table, but not need to write it
>>>> anymore. And will create the _vm file.
>>>>
>>>> I think we really want to create _vm file as well as set PD_ALL_VISIBLE,
>>>> but I don't know the best way to do that. Set a flag somewhere and then
>>>> create it in bulk at the end of the transaction? Set it bit by bit as the
>>>> pages are extended and initialized?
>>>
>>>
>>> Easy enough to do it at the end of the COPY FREEZE in one step.
>>
>>
>> Here, we might want to consider that setting bit in visibility map
>> will generate WAL log whereas Copy Freeze otherwise skip WAL
>> when wal_level is less than archive. This can lead to extra disk
>> writes which can slow down Copy Freeze, but OTOH that might
>> be acceptable.
>
>
> I'm building the map as I go, in the latest version of this patch I'm
> working on.

Hi Simon,

Is this still on your radar? If you would like someone else to pick
it up, can you post the WIP patch you have?

Thanks,

Jeff