Re: max_slot_wal_keep_size and wal_keep_segments

On 2020/07/20 21:21, David Steele wrote:
> On 7/20/20 6:02 AM, Fujii Masao wrote:
>>
>>
>> On 2020/07/20 13:48, Fujii Masao wrote:
>>>
>>>
>>> On 2020/07/17 20:24, David Steele wrote:
>>>>
>>>> On 7/17/20 5:11 AM, Fujii Masao wrote:
>>>>>
>>>>>
>>>>> On 2020/07/14 20:30, David Steele wrote:
>>>>>> On 7/14/20 12:00 AM, Fujii Masao wrote:
>>>>>>>
>>>>>>> The patch was no longer applied cleanly because of recent commit.
>>>>>>> So I updated the patch. Attached.
>>>>>>>
>>>>>>> Barring any objection, I will commit this patch.
>>>>>>
>>>>>> This doesn't look right:
>>>>>>
>>>>>> +   the <xref linkend="guc-wal-keep-size"/> most recent megabytes
>>>>>> +   WAL files plus one WAL file are
>>>>>>
>>>>>> How about:
>>>>>>
>>>>>> +   <xref linkend="guc-wal-keep-size"/> megabytes of
>>>>>> +   WAL files plus one WAL file are
>>>>>
>>>>> Thanks for the comment! Isn't it better to keep "most recent" part?
>>>>> If so, what about either of the followings?
>>>>>
>>>>> 1. <xref linkend="guc-wal-keep-size"/> megabytes of WAL files plus
>>>>>      one WAL file that were most recently generated are kept all time.
>>>>>
>>>>> 2. <xref linkend="guc-wal-keep-size"/> megabytes + <xref linkend="guc-wal-segment-size"> bytes
>>>>>      of WAL files that were most recently generated are kept all time.
>>>>
>>>> "most recent" seemed implied to me, but I see your point.
>>>>
>>>> How about:
>>>>
>>>> +   the most recent <xref linkend="guc-wal-keep-size"/> megabytes of
>>>> +   WAL files plus one additional WAL file are
>>>
>>> I adopted this and pushed the patch. Thanks!
>>>
>>> Also we need to update the release note for v13. What about adding the following?
>>>
>>> ------------------------------------
>>> Rename configuration parameter wal_keep_segments to wal_keep_size.
>>>
>>> This allows how much WAL files to retain for the standby server, by bytes instead of the number of files.
>>> If you previously used wal_keep_segments, the following formula will give you an approximately equivalent setting:
>>>
>>> wal_keep_size = wal_keep_segments * wal_segment_size (typically 16MB)
>>> ------------------------------------
>
> I would rework that first sentence a bit. How about:
>
> + This determines how much WAL to retain for the standby server,
> + specified in megabytes rather than number of files.
>
> The rest looks fine to me.

Thanks for the review!
I adopted your suggestion in the updated version of the patch and pushed it.

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION