From: | Kevin Grittner <kgrittn(at)gmail(dot)com> |
---|---|
To: | Edson Richter <edsonrichter(at)hotmail(dot)com> |
Cc: | "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Overhead changing varchar(2000) to text |
Date: | 2015-12-09 23:31:48 |
Message-ID: | CACjxUsNs9jiy4-PCjQgcZLimU-6Xw7zqxyCoAKAr-DzeTp-0NA@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
On Wed, Dec 9, 2015 at 5:17 PM, Kevin Grittner <kgrittn(at)gmail(dot)com> wrote:
> On Wed, Dec 9, 2015 at 5:13 PM, Edson Richter <edsonrichter(at)hotmail(dot)com> wrote:
>
>> I do have several tables that uses varchar(2000) as store for remarks.
>> Lately, one customer need to store more than 2000 characteres, and I'm
>> considering changing from varchar(2000) to text.
>>
>> What is the overhead?
>
> None -- they are stored in exactly the same format; the only
> difference is whether the length is limited.
I probably should have mentioned that an ALTER TABLE to change the
column type from varchar(2000) to text does not rewrite the data
(since it is in the same format) -- it just changes the catalogs to
reflect the lack of a limit on length. Changing the other way
would require a pass to check that all existing data passes the
length check.
>> Is there any place where I can learn about storage impacto for each data
>> type?
>
> http://www.postgresql.org/docs/current/interactive/datatype-character.html
While it's fairly technical, you might also be interested in this:
http://www.postgresql.org/docs/current/interactive/storage-toast.html
--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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