于 2013-09-04 23:41, Jeff Janes 回复:
On Tue, Sep 3, 2013 at 9:08 PM, <wangs...@highgo.com.cn> wrote:
Hi, Hackers!
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.
Anyone has more idea about this, please come to talk about this!
Jeff Janes <jeff.ja...@gmail.com> wrote:
This was fixed in version 9.2. You must be using an older version.
Cheers,
Jeff
Thanks for your reply.
To declare a column of type numeric use the syntax:
NUMERIC(precision, scale).
What I said is this scale,not yours.
I made a test on PG9.2, as fellow:
postgres=# select version();
version
--------------------------------------------------------------------------------------------------------------
PostgreSQL 9.2.4 on x86_64-unknown-linux-gnu, compiled by gcc (GCC)
4.7.2 20121109 (Red Hat 4.7.2-8), 64-bit
(1 row)
postgres=# create table tt(t1 numeric(10,5));
CREATE TABLE
postgres=# insert into tt values (2.56);
INSERT 0 1
postgres=# select pg_relation_filepath('tt');
pg_relation_filepath
----------------------
base/12914/16384
(1 row)
postgres=# alter table tt alter COLUMN t1 type numeric(10,6);
ALTER TABLE
postgres=# select pg_relation_filepath('tt');
pg_relation_filepath
----------------------
base/12914/16387
(1 row)
So thers's no need to rewrite the table.
Wang Shuo
HighGo Software Co.,Ltd.
September 5, 2013
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
