Re: [PATCH] Add features to pg_stat_statements

2020-11-17 01:46 に Fujii Masao さんは書きました:
> On 2020/11/16 12:22, Seino Yuki wrote:
>>> Thanks for updating the patch!
>>>
>>> +        pgss_info->dealloc = 0;
>>> +        SpinLockInit(&pgss_info->mutex);
>>> +        Assert(pgss_info->dealloc == 0);
>>>
>>> Why is this assertion check necessary? It seems not necessary.
>>>
>>> +    {
>>> +        Assert(found == found_info);
>>>
>>> Having pgssSharedState and pgssInfoCounters separately might make
>>> the code a bit more complicated like the above? If this is true, what
>>> about
>>> including pgssInfoCounters in pgssSharedState?
>>>
>>> PGSS_FILE_HEADER needs to be changed since the patch changes
>>> the format of pgss file?
>>>
>>> +    /* Read pgss_info */
>>> +    if (feof(file) == 0)
>>> +        if (fread(pgss_info, sizeof(pgssInfoCounters), 1, file) !=
>>> 1)
>>> +            goto read_error;
>>>
>>> Why does feof(file) need to be called here?
>>>
>>> +pgss_info_update(void)
>>> +{
>>> +    {
>>>
>>> Why is the second "{" necessary? It seems redundant.
>>>
>>> +pgss_info_reset(void)
>>> +{
>>> +    {
>>>
>>> Same as above.
>>>
>>> +pg_stat_statements_info(PG_FUNCTION_ARGS)
>>> +{
>>> +    int64        d_count = 0;
>>> +    {
>>>
>>> Same as above.
>>>
>>> +        SpinLockAcquire(&c->mutex);
>>> +        d_count = Int64GetDatum(c->dealloc);
>>> +        SpinLockRelease(&c->mutex);
>>>
>>> Why does Int64GetDatum() need to be called here? It seems not
>>> necessary.
>>>
>>> +   <varlistentry>
>>> +    <term>
>>> +     <function>pg_stat_statements_info() returns bigint</function>
>>> +     <indexterm>
>>> +      <primary>pg_stat_statements_info</primary>
>>> +     </indexterm>
>>> +    </term>
>>>
>>> Isn't it better not to expose pg_stat_statements_info() function in
>>> the
>>> document because pg_stat_statements_info view is enough and there
>>> seems no use case for the function?
>>>
>>> Regards,
>>
>> Thanks for the comment.
>> I'll post a fixed patch.
>> Due to similar fixed, we have also merged the patches discussed in the
>> following thread.
>> https://commitfest.postgresql.org/30/2738/
>
> I agree that these two patches should use the same infrastructure
> because they both try to add the global stats for pg_stat_statements.
> But IMO they should not be merged to one patch. It's better to
> develop them one by one for ease of review. Thought?
>
> So I extracted the "dealloc" part from the merged version of your
> patch.
> Also I refactored the code and applied some cosmetic changes into
> the patch. Attached is the updated version of the patch that implements
> only "dealloc" part. Could you review this version?
>
> Regards,

Thank you for posting the new patch.

I checked "regression test" and "document" and "operation of the view".
No particular problems were found.

I just want to check one thing: will the log output be unnecessary this
time?
Quotes from v2.patch
>
> + {
> entry_dealloc();
> + /* Update pgss_info */
> + {
> + volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
> + SpinLockAcquire(&s->mutex);
> + s->pgss_info.dealloc += 1; /* increment dealloc count */
> + SpinLockRelease(&s->mutex);
> + }
> + ereport(LOG,
> + (errmsg("The information in pg_stat_statements has been
> deallocated.")));
> + }

Regards.