Re: [HACKERS] log_checkpoint's "0 transaction log file(s) added" is extremely misleading

2016-01-26 Thread Fujii Masao 
On Fri, Jan 22, 2016 at 11:33 AM, Andres Freund  wrote:
> On January 22, 2016 3:29:44 AM GMT+01:00, Simon Riggs  
> wrote:
>>On 22 January 2016 at 01:12, Andres Freund  wrote:
>>
>>> Hi,
>>>
>>> While in theory correct, I think $subject is basically meaningless

What about just changing "added" to "preallocated" to avoid the confusion?

>>> because other backends may have added thousands of new segments. Yes,
>>it
>>> wasn't the checkpointer, but that's not particularly relevant
>>> imo. Additionally, afaics, it will only ever be 0 or 1.
>>>
>>
>>Even better, we could make it add >1
>
> That'd indeed be good, but I don't think it really will address my complaint: 
> We'd still potentially create new segments outside the prealloc call. 
> Including from within the checkpointer, when flushing WAL to be able to write 
> out a page.

IMO it's more helpful to display such information in something like
pg_stat_walwriter view rather than checkpoint log message.

Regards,

-- 
Fujii Masao


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Re: [HACKERS] log_checkpoint's "0 transaction log file(s) added" is extremely misleading

2016-01-21 Thread Andres Freund 
On January 22, 2016 3:29:44 AM GMT+01:00, Simon Riggs  
wrote:
>On 22 January 2016 at 01:12, Andres Freund  wrote:
>
>> Hi,
>>
>> While in theory correct, I think $subject is basically meaningless
>> because other backends may have added thousands of new segments. Yes,
>it
>> wasn't the checkpointer, but that's not particularly relevant
>> imo. Additionally, afaics, it will only ever be 0 or 1.
>>
>
>Even better, we could make it add >1

That'd indeed be good, but I don't think it really will address my complaint: 
We'd still potentially create new segments outside the prealloc call. Including 
from within the checkpointer, when flushing WAL to be able to write out a page.

Andres

---
Please excuse brevity and formatting - I am writing this on my mobile phone.


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Re: [HACKERS] log_checkpoint's "0 transaction log file(s) added" is extremely misleading

2016-01-21 Thread Simon Riggs 
On 22 January 2016 at 01:12, Andres Freund  wrote:

> Hi,
>
> While in theory correct, I think $subject is basically meaningless
> because other backends may have added thousands of new segments. Yes, it
> wasn't the checkpointer, but that's not particularly relevant
> imo. Additionally, afaics, it will only ever be 0 or 1.
>

Even better, we could make it add >1


> I think we should either remove that part of the log output, or make it
> display the number of segments added since the beginning of the
> checkpoint.
>

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Simon Riggshttp://www.2ndQuadrant.com/

PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

[HACKERS] log_checkpoint's "0 transaction log file(s) added" is extremely misleading

2016-01-21 Thread Andres Freund 
Hi,

While in theory correct, I think $subject is basically meaningless
because other backends may have added thousands of new segments. Yes, it
wasn't the checkpointer, but that's not particularly relevant
imo. Additionally, afaics, it will only ever be 0 or 1.

I think we should either remove that part of the log output, or make it
display the number of segments added since the beginning of the
checkpoint.

Greetings,

Andres Freund


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