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From:Marc Alff Date:May 19 2009 4:07pm
Subject:Re: Performance Schema (WL#2360): OBJECT_INSTANCE_BEGIN column for
files
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Hi Guilhem

Guilhem Bichot wrote:
> Hello Marc,
> 
> I see that for files, object_instance_begin is always 0 in my tests:
> 
> mysql> select * from EVENTS_WAITS_SUMMARY_BY_INSTANCE where
> object_instance_begin=0 order by 1 ;
>
> +---------------------------------------------+-----------------------+------------+----------------+----------------+----------------+----------------+
> 
> | EVENT_NAME                                  | OBJECT_INSTANCE_BEGIN |
> COUNT_STAR | SUM_TIMER_WAIT | MIN_TIMER_WAIT | AVG_TIMER_WAIT |
> MAX_TIMER_WAIT |
>
> +---------------------------------------------+-----------------------+------------+----------------+----------------+----------------+----------------+
> 
> | wait/io/file/maria/control                  |                     0 |
>          6 |      113417304 |        1987986 |       18902884 | 62948886 |
> | wait/io/file/maria/log_descriptor_directory |                     0 |
>          2 |       85008924 |        5579574 |       42504462 | 79429350 |
> | wait/io/file/maria/recovery_trace           |                     0 |
>          7 |      182696514 |         780780 |       26099502 | 60282222 |
> | wait/io/file/myisam/dfile                   |                     0 |
>          1 |       12882870 |       12882870 |       12882870 | 12882870 |
> | wait/io/file/myisam/dfile                   |                     0 |
>          1 |       12924912 |       12924912 |       12924912 | 12924912 |
> | wait/io/file/myisam/dfile                   |                     0 |
>          4 |       24180156 |        1285284 |        6045039 | 13159146 |
> | wait/io/file/myisam/dfile                   |                     0 |
>          3 |       17951934 |        1327326 |        5983978 | 13975962 |
> 
> As this is a "by_instance" table (one line per MyISAM data file, the
> dfile lines above), I expected a discriminating information to be
> present, so that I can know, among the 3 dfile above, which one belongs
> to what; for this, I expected file names to show up.
> I see that for mutex instances, the column is not 0.

object_instance_begin is only an address, it can not be a file name.

For files, there is no "identity" pointer that can be used, since there
is no file object the code can use (FILE* is a file handle, not
representative of the underlying file itself).

So, I used the address of the PFS_FILE* structure itself for:
- EVENTS_WAITS_CURRENT.OBJECT_INSTANCE_BEGIN
- EVENTS_WAITS_HISTORY.OBJECT_INSTANCE_BEGIN
- EVENTS_WAITS_HISTORY_LONG.OBJECT_INSTANCE_BEGIN
- EVENTS_WAITS_SUMMARY_BY_INSTANCE.OBJECT_INSTANCE_BEGIN

so that there is always a discriminant in OBJECT_INSTANCE_BEGIN,
globally unique

Now, this raise the question about adding an OBJECT_INSTANCE_BEGIN
column in FILE_INSTANCES, so that we have both the file name and
address, to join data ...

The same question will arise for tables, where a table can be named:
- either by schema + name
- or by object_instance_begin (the address of the table share),

when we get to something like TABLE_INSTANCES, and summary by tables.

Peter, any opinion ?



Thread
Performance Schema (WL#2360): OBJECT_INSTANCE_BEGIN column for filesGuilhem Bichot18 May
  • Re: Performance Schema (WL#2360): OBJECT_INSTANCE_BEGIN column forfilesMarc Alff19 May
    • Re: Performance Schema (WL#2360): OBJECT_INSTANCE_BEGIN column forfilesPeter Gulutzan22 May
    • Re: Performance Schema (WL#2360): OBJECT_INSTANCE_BEGIN column forfilesPaul DuBois26 May
      • Re: Performance Schema (WL#2360): OBJECT_INSTANCE_BEGIN column forfilesMarc Alff26 May