Re: Is it necessary to rewrite table while increasing the scale ofdatatype numeric??? - Mailing list pgsql-hackers

From wangshuo@highgo.com.cn
Subject Re: Is it necessary to rewrite table while increasing the scale ofdatatype numeric???
Date
Msg-id 007bc903ebd09778bbedbd2282cf0916@highgo.com.cn
Whole thread Raw
In response to Re: Is it necessary to rewrite table while increasing the scale of datatype numeric???  (Noah Misch <noah@leadboat.com>)
Responses Re: Is it necessary to rewrite table while increasing the scale of datatype numeric???
List pgsql-hackers
于 2013-09-04 19:30, Noah Misch 回复:
> 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.




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