There seems to be an optimizer problem in 5.1, if you put a NULL in the IN clause of a SELECT. For example, given the following table:

CREATE TABLE foo (
    a INT NOT NULL AUTO_INCREMENT,
    PRIMARY KEY (a)
);

Compare these two EXPLAINs:

mysql> EXPLAIN * FROM foo WHERE a IN (160000, 160001, 160002)\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: foo
         type: range
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 4
          ref: NULL
         rows: 3
        Extra: Using where
1 row in set (0.06 sec)
mysql> EXPLAIN SELECT * FROM foo WHERE a IN (NULL, 160000, 160001, 160002)\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: foo
         type: ALL
possible_keys: PRIMARY
          key: NULL

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Problem

With the release of MySQL 5.1, many DBAs are going to be scheduling downtime to upgrade their MySQL Server. As with all upgrades between major version numbers, it requires one of two upgrade paths:

• Dump/reload: The safest method of upgrading, but it takes out your server for quite some time, especially if you have a large data set.
• mysql_upgrade: A much faster method, but it can still be slow for very large data sets.

I’m here to present a third option. It requires minimal application downtime, and is reasonably simple to prepare for and perform.

Preparation

First of all, you’re going to need a second server (which I’ll refer to as S2). It will act as a ’stand-in’, while the main server (which I’ll refer to as S1) is upgraded. Once S2 is ready to go, you can

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MySQL 5.1 has a lot of nice new features, partitioning, event scheduler, dynamic logging, etc... Most of these require changing some application code or design logic to make use of them. However, there is a few new features that almost every user of InnoDB can take advantage of right away and that is the ability to set MySQL so that less locking is required for many statements in InnoDB. There are a few changes which make this possible.

The first one is the new auto_increment locking for InnoDB. There is a good article which talks about this here and a large section the in the manual.

In MySQL 5.0 and previous, InnoDB used a special



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There’s a change of behaviour in MySQL 5.1.31 for Row Based Replication, if you have InnoDB transactions that also write to a MyISAM (or other non-transactional engine) table. It’s a side effect of fixing Bug #40116. Take this simple example:

Transaction 1: INSERT INTO myisam_tbl (item, val) VALUES (1, 0);
Transaction 1: INSERT INTO innodb_tbl (item, val) VALUES (1, -1), (2, -1);
Transaction 1: START TRANSACTION;
Transaction 1: UPDATE myisam_tbl SET val=val+1 WHERE item=1;
Transaction 1: UPDATE innodb_tbl SET val=( SELECT val FROM myisam_tbl WHERE item=1 ) WHERE item=1;
Transaction 2: START TRANSACTION;
Transaction 2: UPDATE myisam_tbl SET val=val+1 WHERE item=1;
Transaction 2: UPDATE innodb_tbl SET val=( SELECT val FROM myisam_tbl WHERE item=1 ) WHERE

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So being that I am a support engineer with Sun/MySQL, I figured I would chime in with my opinion of MySQL 5.1 GA so far since I have been using it for a while. For history, I have been with MySQL AB/Sun since the 4.0 release cycle. This post does not represent any official views of my employer, Sun Microsystems, and all such disclaimers.

First off, I want to say that Sun assisted greatly with MySQL 5.1. I think it is a much better release than it would have been with MySQL AB doing the release. I do think this will continue in the future from everything I have experienced and seen so far. Sun knows how to make solid software.


So do I think that 5.1 was released too early? Not at all from my experiences of the MySQL releases. 5.1 is fairing quite well, and I think everyone that has a reason to upgrade to it (such as less locking for InnoDB




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Do you remember Guy Adams? He was one of the winners of the “5.1 Use Case Competition”, ending up on position #2. Guess what: He has a webinar coming up tomorrow, by the title Deploying MySQL in a High Performance Satellite Network Management Environment by Parallel.
 
Guy works with Parallel Ltd. in Milton Keynes in the UK. You may also want to read up on

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Here is my personal recipe for celebrating MySQL 5.1 GA (called “Five shot one“):

Ingredients:

• Kalashnikov vodka from Izhevsk, Udmurtia (

I suspect that few of the readers of my blog have missed it, but MySQL 5.1 is GA (http://www.mysql.com/products/enterprise/server.html" target="_blank). And I suspect it was no surprise to my readers, nor those of Giuseppe, the Community Team Lead. Nor those who read Sheeri’s blog, with the picture of Dups unmistakably setting GA date expectations at the OpenSQL Camp a number of weeks ago.

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With the delivery of MySQL 5.1 GA, our release policy sees a couple of changes in relation to that of MySQL 5.0.

First, initially we will deliver both MySQL Enterprise Server and MySQL Community Server in parallel. The bug fixes to the initial MySQL 5.1 GA releases will thus be delivered also in binary form for both MySQL Community Server and MySQL Enterprise Server.

Second, after a period of time, we will revert to the different release schedule for MySQL Enterprise Server and MySQL Community Server that we have been using. MySQL Enterprise Server will have more frequent binary releases. However, at this point, we do not have

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MySQL 5.1 is here! It’s announced! And it’s time for the overall winner, Position 1 in the MySQL 5.1 Use Case Competition.

1. Greg Haase (Lotame Solutions Inc., Elkridge, Maryland, USA): Using Partitioning and Event Scheduler to Prune Archive Tables. See Greg’s DevZone article, and his blog.

Thanks and congratulations,

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The GA announcement of MySQL 5.1 is coming, and for downloading, it’s already available, as I hope you have noticed from Giuseppe’s blog. We continue our preparations, this time by announcing Position 2 in the MySQL 5.1 Use Case Competition.

2. Guy Adams (Parallel Ltd., Milton Keynes, United Kingdom): Using Partitioning to Manage Satellite Networks. See Guy’s DevZone article.

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The GA announcement of MySQL 5.1 is getting closer by the minute! So it’s time for Position 3 in the MySQL 5.1 Use Case Competition.

3. Corrado Pandiani (Football Club Internazionale Milano Spa, Milan, Italy): Using Partitioning and Event Scheduler for online logging & real-time stats. See Corrado’s DevZone article, and his blog.

Thanks and congratulations, Corrado! I hope you are in a position to take

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The GA announcement of MySQL 5.1 is close, so close that we’re seeding the mirrors (I hope you noted Giuseppe’s blog entry)! So it’s time for Position 4 in the MySQL 5.1 Use Case Competition.

4. Volker Oboda (TeamDrive Systems GmbH, Hamburg, Germany): Using the Pluggable API for TeamDrive. See Volker’s DevZone article, and

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With the GA announcement of MySQL 5.1 coming up, we have picked the winners in the MySQL 5.1 Use Case Competition.

To keep you in suspense, let me first announce those on positions 5 to 10:

5. Fourat Zouari (TriTUX.com, Tunis, Tunisia): Using Partitioning for Data Warehousing. See Fourat’s DevZone article, and

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