Comments on: Should you name indexes while doing ALTER TABLE ?

By: krteQ

krteQ — Tue, 10 Jun 2008 15:18:05 +0000

I just add, that this problem doubles while using FOREIGN KEYS. You just drop a foreign key and think the DELETE will perform how you expect, but…

By: Gregory Haase

Gregory Haase — Fri, 30 May 2008 20:49:56 +0000

I was really surprised to discover that mySQL does not support naming the primary key. If you select contraint_name from information_schema.table_constraints, you get an aweful lot of constraints named “PRIMARY”. Do we really need this here, we have another column in the same table called constraint_type which happily tells us it’s a PRIMARY KEY.

But what surprised me the most was the fact that the following syntax does not produce an error:

CREATE TABLE `test`.`testing`
( testing_id INT NOT NULL auto_increment,
PRIMARY KEY `pk_testing` (`testing_id`)
);

You table will be happily created with primary key, but when you do a show create table, you get the following:

CREATE TABLE `testing` (
`testing_id` int(11) NOT NULL AUTO_INCREMENT,
PRIMARY KEY (`testing_id`)
)

As far as naming conventions, I usually name my foreign key constraints fk__ and my indexes i__# (and up until about 10 minutes ago I was naming my primary key constraints pk_).

By: peter

peter — Thu, 29 May 2008 17:05:54 +0000

Olexandr,

Thanks I changed prefix to suffix.

By: Olexandr Melnyk

Olexandr Melnyk — Thu, 29 May 2008 15:43:36 +0000

> No, it won’t. It stops at 64.
> (Don’t ask me how I know…)

This applies not just to duplicate indexes, but is a generic MyISAM limitation.

By: Eric

Eric — Thu, 29 May 2008 15:38:15 +0000

> What happens if you try to create the same index without specifying index
> name? MySQL will happily create (and maintain) as many duplicate keys as you
> like without even giving you a warning:

No, it won’t. It stops at 64.
(Don’t ask me how I know…)

- Eric

By: Olexandr Melnyk

Olexandr Melnyk — Thu, 29 May 2008 15:34:58 +0000

> it will add numeric prefix to it

It’s a postfix or a suffix, but not a prefix

By: peter

peter — Thu, 29 May 2008 05:32:21 +0000

Monty,

I surely agree. Though I would make sure the index type is same as well (it is OK to have column indexes as normal BTREE index and FullText for example)
Regarding but reports – you should be in the best position to post them as MySQL/Sun employee.

I think I proposed fixing first one but it did not ended up going any where.

By: Monty Taylor

Monty Taylor — Thu, 29 May 2008 05:24:24 +0000

Seems like there are a couple of bug/feature requests in this post too. (to me, at least)

- MySQL allows duplicate identical index creation

(I can see no reason why two indexes on the exact same column would be useful – but maybe I’m wrong)

- MySQL creates crap auto_generated names

Instead of just using the first column name as the index name, how about firstcolumn_secondcolumn_thirdcolumn – etc – until it runs out of space? This is a common practice in the field anyway. (As is prefixing idx_ – although I don’t like this very much myself)

Anybody want to file there?

By: peter

peter — Thu, 29 May 2008 05:17:58 +0000

Peter,

May be if you get too conservative this is the case, Though you can find a lot of “indexes” used as plural for index.
Some people say this is also preferred form these days:
http://wiki.answers.com/Q/What_is_the_plural_of_index

By: Peter A. Shevtsov

Peter A. Shevtsov — Thu, 29 May 2008 04:01:48 +0000

The plural form of the word “index” is “indices”