Re: Is it necessary to rewrite table while increasing the scale of datatype numeric???

On Thu, Sep 05, 2013 at 11:07:43AM +0800, wangshuo@highgo.com.cn wrote:
> ??? 2013-09-04 19:30, Noah Misch ??????:
>> On Wed, Sep 04, 2013 at 12:08:48PM +0800, wangshuo@highgo.com.cn  
>> wrote:
>>> I find that it takes a long time when I increase the scale of a  
>>> numeric
>>> datatype.
>>> By checking the code, I found that's because it needs to rewrite  
>>> that
>>> table's file.
>>> After checking that table's data file, I found only parameter  
>>> n_header
>>> changed.
>>> And, I found the data in that numeric field never changed.
>>> So I thank It's not necessary to rewrite the table's file in this  
>>> case.
>>
>
> Noah Misch <noah@leadboat.com> wrote:
>> n_header is part of the numeric field's data.  That's not just  
>> pedantry: the
>> display scale stored in n_header affects how numeric_out() formats the 
>> value.
>
> Thanks for your reply.
>
> Just because of what you said, I think increasing scale only lead to  
> differently
> diaplay. There's no difference between 5.25 and 5.2500 in use.
> So thers's no need to rewrite the table.

Right or wrong, our numeric type caters to applications that do care about the
difference between those outputs.  I grant that others do not care.

-- 
Noah Misch
EnterpriseDB                                 http://www.enterprisedb.com