From: Jaime Casanova <systemguards@gmail.com>
To: fmiddleton@verizon.net <fmiddleton@verizon.net>
Cc: pgsql-sql@postgresql.org
Subject: Re: can UNIQUEness of TEXT datatype really be guaranteed?
Date: Tue, 22 Nov 2005 12:45:36 -0500
Message-ID: <c2d9e70e0511220945x57b9e965l283de897665497bb@mail.gmail.com> (raw)
In-Reply-To: <2238206.1132680900217.JavaMail.root@vms068.mailsrvcs.net>
References: <2238206.1132680900217.JavaMail.root@vms068.mailsrvcs.net>
On 11/22/05, fmiddleton@verizon.net <fmiddleton@verizon.net> wrote:
> I am in the process re-implementing some pgsql table declarations into a MySQL database. I have this one line where I say
> ...
> fieldname TEXT UNIQUE,
> ...
> in my pgsql table because I want to ensure that no one enters the same thing in this field and I didn't choose VARCHAR type because I have no idea how possibly long I might need to let the field be...
>
> ... but MySQL doesn't like this because a TEXT datatype is considered a BLOB that can't be indexed and it can't guarantee will be UNIQUE apparently...
>
> So I can't help but wonder, can Postgres really guarantee a TEXT field to be UNIQUE... or is declaring a TEXT field UNIQUE something an uninformed, novice user would do?... or is it something indicative of the strength and/or weeknesses that separate the functionality of the two DBMSs.
>
> Ferindo Middleton
>
TEXT fileds can be indexed in postgres and AFAIK it can be indexed
with a unique index (and i don't see any good reason to think it can't
guarantee uniqueness)...
but you have a limitation, btree index rows can only have certain size
(i don't remember the numbers now)... so if you exceed that size (and
in a text field you can) you will get an error... you have to control
within your application that...
--
Atentamente,
Jaime Casanova
(DBA: DataBase Aniquilator ;)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-sql@postgresql.org
Cc: systemguards@gmail.com, fmiddleton@verizon.net
Subject: Re: can UNIQUEness of TEXT datatype really be guaranteed?
In-Reply-To: <c2d9e70e0511220945x57b9e965l283de897665497bb@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox