Comments on: Stored Function to generate Sequences

By: Silvio Delgado

Silvio Delgado — Thu, 14 Oct 2010 15:47:25 +0000

Very good! It works fine!

Thanks a lot.

By: David Smith

David Smith — Thu, 07 Oct 2010 21:04:54 +0000

Well, I see I’m a little late to the party…

I’m wondering if I can use something like this for two user classes sharing the same int table row, by auto-incrementing in ranges, e.g. user class one has user_id in the 0 – 1000 range, and user class two in the > 1000 range.

The reason I would need to do this instead of just cresting another table for the new user class, is because I am attempting to modify an existing, and rather complicated (to me) php app.

What sort of syntax would I need to use, given that I want to modify transactions to/from an existing row rather than CREATE TABLE (as your example does)? I just want to write and filter on queries for user_id’s from the two seperate ranges, and auto-increment new users of the two clases in their respective ranges.

Thanks!

By: Bruno Braga

Bruno Braga — Sat, 24 Oct 2009 00:15:13 +0000

Yeah, I did a stress testing on this, and worked fine (on InnoDB as well).

By: Baron Schwartz

Baron Schwartz — Fri, 23 Oct 2009 12:23:59 +0000

MyISAM has table-level locking. It works.

By: Bruno Braga

Bruno Braga — Thu, 22 Oct 2009 07:06:04 +0000

This code does not handle concurrency/locking. Has anyone tested this against overloaded systems? I have the feeling it will not work properly.

By: saroj

saroj — Tue, 02 Jun 2009 05:15:38 +0000

thanks peter code worked

By: Using Multiple Sequences in a Table « Everything MySQL

Using Multiple Sequences in a Table « Everything MySQL — Tue, 16 Sep 2008 18:32:21 +0000

[...] issues.Â After lot of trials, debates and finally referring Planet MySQL, I went ahead with this suggestion by Peter from MySQL Performance Blog and some help from here. CREATE TABLE sequences ( event_id [...]

By: Justin Huff

Justin Huff — Thu, 31 Jul 2008 01:22:16 +0000

I typically see the update step written like:
UPDATE sequence SET nValue=last_insert_id(nValue+1) WHERE strName=?

I’d like to allow servers the option of asking for more than one id per call by moving the increment step outside the last_insert_id:
UPDATE sequence SET nValue=last_insert_id(nValue)+? WHERE strName=?

The value in the table shifts from being the ‘last id handed out’ to ‘the next id to hand out’. That way requesters don’t need to know how big the last block was.

Am I missing something here?
Thanks!

By: Links for Wed 7 May 2008 - Joseph Scott’s Blog

Links for Wed 7 May 2008 - Joseph Scott’s Blog — Thu, 08 May 2008 16:52:56 +0000

[...] Stored Function to generate Sequences | MySQL Performance Blog – You could combine this with an INSERT trigger and get even more auto_increment like functionality. Tags: database mysql sequence [...]

By: peter

peter — Fri, 04 Apr 2008 01:41:33 +0000

Arjen,

Indeed insert on dup key updates saves you from initialization though I’m wondering what way would be the faster.
Though I guess there would not be any significant difference here.