maria-discuss team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxxx>]

Hi, Oleg!

On Aug 18, Oleg Tsarev wrote:
> 
> Hello,
> 
> I don't understand how right work with decimal type.
> As you talk, i change column types from CHAR(...) to DECIMAL in my patch:
> http://www.percona.com/docs/wiki/patches:response_time_distribution
> 
> Now i have trouble with decimal precision/scale.
> 
> Here is my definition of system table INFORMATION_SCHEMA.QUERY_RESPONSE_TIME:
> 
> ST_FIELD_INFO query_response_time_fields_info[] =
>   {
>     {"TIME",  MY_INT64_NUM_DECIMAL_DIGITS, MYSQL_TYPE_LONGLONG, 0, MY_I_S_UNSIGNED, "time",  SKIP_OPEN_TABLE },
>     {"COUNT", MY_INT32_NUM_DECIMAL_DIGITS, MYSQL_TYPE_LONG,     0, MY_I_S_UNSIGNED, "count", SKIP_OPEN_TABLE },
>     {"TOTAL", MY_INT64_NUM_DECIMAL_DIGITS, MYSQL_TYPE_LONGLONG, 0, MY_I_S_UNSIGNED, "total", SKIP_OPEN_TABLE },
>     {0,       0,                           MYSQL_TYPE_STRING,   0, 0,  0,       SKIP_OPEN_TABLE }
>   };
> 
> So, i want use DECIMAL(20,6) for columns time and total, and
> DECIMAL(14,0) for columns count.
> 
> 1) Does above definiton correct, or should include some information
> about precision/scale?

It is not correct. If you want to use DECIMAL you need to write
MYSQL_TYPE_DECIMAL, not MYSQL_TYPE_LONG or MYSQL_TYPE_LONGLONG.

See sql_show.cc or sql_profile.cc for other information_schema tables
with DECIMAL columns.
 
Regards,
Sergei