Re: Feature improvement for pg_stat_statements - Mailing list pgsql-hackers

On 2020/11/30 12:08, Seino Yuki wrote:
> 2020-11-27 22:39 に Fujii Masao さんは書きました:
>> On 2020/11/27 21:39, Seino Yuki wrote:
>>> 2020-11-27 21:37 に Seino Yuki さんは書きました:
>>>> 2020-11-16 12:28 に Seino Yuki さんは書きました:
>>>>> Due to similar fixed, we have also merged the patches discussed in the
>>>>> following thread.
>>>>> https://commitfest.postgresql.org/30/2736/
>>>>> The patch is posted on the 2736 side of the thread.
>>>>>
>>>>> Regards.
>>>>
>>>
>>> I forgot the attachment and will resend it.
>>>
>>> The following patches have been committed and we have created a
>>> compliant patch for them.
>>> https://commitfest.postgresql.org/30/2736/
>>>
>>> Please confirm.
>>
>> Thanks for updating the patch! Here are review comments from me.
>>
>> +    OUT reset_exec_time TIMESTAMP WITH TIME ZONE
>>
>> I prefer "stats_reset" as the name of this column for the sake of
>> consistency with the similar column in other stats views like
>> pg_stat_database.
>>
>> Isn't it better to use lower cases for "TIMESTAMP WITH TIME ZONE"
>> because other DDLs in pg_stat_statements do that for the declaraion
>> of data type?
>>
>> @@ -565,6 +568,8 @@ pgss_shmem_startup(void)
>>          pgss->n_writers = 0;
>>          pgss->gc_count = 0;
>>          pgss->stats.dealloc = 0;
>> +        pgss->stats.reset_exec_time = 0;
>> +        pgss->stats.reset_exec_time_isnull = true;
>>
>> The reset time should be initialized with GetCurrentTimestamp() instead
>> of 0? If so, I think that we can completely get rid of reset_exec_time_isnull.
>>
>> +    memset(nulls, 0, sizeof(nulls));
>>
>> If some entries in "values[]" may not be set, "values[]" also needs to
>> be initialized with 0.
>>
>> MemSet() should be used, instead?
>>
>> +    /* Read dealloc */
>> +    values[0] = stats.dealloc;
>>
>> Int64GetDatum() should be used here?
>>
>> +    reset_ts = GetCurrentTimestamp();
>>
>> GetCurrentTimestamp() needs to be called only when all the entries
>> are removed. But it's called even in other cases.
>>
>> Regards,
> 
> Thanks for the review!
> Fixed the patch.

Thanks for updating the patch! Here are another review comments.

+       <structfield>reset_exec_time</structfield> <type>timestamp with time zone</type>

You forgot to update the column name in the doc?

+        Shows the time at which <function>pg_stat_statements_reset(0,0,0)</function> was last called.

What about updating this to something like "Time at which all statistics
in the pg_stat_statements view were last reset." for the sale of
onsistency with the description about stats_reset column in other
tats views?

+    /* Read stats_reset */
+    values[1] = stats.stats_reset;

TimestampTzGetDatum() seems necessary.

+        reset_ts = GetCurrentTimestamp();
          /* Reset global statistics for pg_stat_statements */

Isn't it better to call GetCurrentTimestamp() before taking
an exclusive lwlock, in entry_reset()?

Regards,

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