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Displaying posts with tag: Tech (reset)

Hibernate Query Cache: A Dirty Little Secret
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You Mean, Memory Is Not Infinite?

We're working hard getting MySQL Enterprise Monitor 2.0, featuring Query Analyzer (http://www.mysql.com/trials/enterprise), ready for release. As part of that, we started really ramping up the number of MySQL servers reporting in query data to see how we could scale. Not surprising (to me, anyway), the first efforts did not go so well. My old friend OutOfMemoryError reared its ugly head once again.

Query Cache -- It's More Than Just Results!

We're big (ab)users of hibernate query caching, and more importantly to us the natural id optimized query cache. Firing up the profiler, I was not shocked to see that the
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MySQL and the Missing Rows
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I was doing some multi-threaded, multi-transactional testing for the backend of the MySQL Enterprise Monitor. I came across a weird failure, where it appeared I was able to successfully insert a row, and then (in the same transaction), a select from the same table did not return any rows.

Consider the following transactions:


mysql> create table t1 (id integer primary key auto_increment, name varchar(32) unique) engine=innodb;

a> begin;

b> begin;
b> select * from t1;

a> insert into t1 values(null, 'oldag');

b> insert into t1 values(null, 'oldag) on duplicate key update id=LAST_INSERT_ID(id);
(b blocks)

a> commit;

(b is released)
...
Query OK, 0 rows affected (0.00 sec)
b> select * from t1;
Empty set (0.00 sec)
























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Mysql Error
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I was running an import script today taken from a mysqldump from another user, when I saw an error that looked like this:

ERROR 1005 (HY000) at line 123: Cant create table
 (errno: 150)

This is caused by a mysqldump or export process exporting tables in alphabetical order and not in the order in which they rely on one another. My tables had foreign keys which fail on import if the other table doesn't exist when you create the table with the key. In this case I was only importing six or eight tables so I simply opened the script in a text editor and re-ordered the import blocks. On a bigger scale a more technical solution might be required!

Lorna is an independent web development consultant, writer and trainer, open source project lead and community evangelist. This post was originally published at LornaJane

Hibernate: Cache Queries the Natural Id Way
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I work on the MySQL Enterprise Tools (http://www.mysql.com/products/enterprise/monitor.html) team, formerly of MySQL and now with Sun Microsystems. The 2.0 version of the Enterprise Monitor is well under way. As part of this, the Java server backend has been refactored to utilize Spring and Hibernate. Honestly, I didn't know either one of those technologies before starting this project. Oh, what a fun road it has been...

A big draw for using an off-the-shelf ORM was so that we didn't have to write our own (kind of bad and slightly wrong -- those darn transactions) caching implementations for the custom one-off ORM that existed previously. A lot of our internal meta-model is very static, so clearly caching

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Certified MySQL 5.1 Cluster Administrator
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Yesterday I passed the CMCDEV exam.

I only used the study guide (previous entry) and the official manual to prepare for the exam.

The study guide is a good preparation for the exam.(Thanks to Roland Bouman and all other people involved with the book. The only minor issue with the book is that it didn't feel finished. Images which should've been printed in high quality and some phrases about a CD which is absent (All listed/fixed in the errata)

I filed a few bug reports while studying. (patched included :) )

So now let's wait for MySQL 5.1 to become GA.
FOSDEM
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MySQL 5.1 Cluster Certification Study Guide
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Today I received the "MySQL 5.1 Cluster Certification Study Guide".

I will compare this book to the "MySQL 5.0 Certification Study Guide" from MySQL Press. This is the book I used to study for the MCDEV (Certified Developer) and MCDBA (Certified DBA) exams.

The MySQL study guide was published by MySQL Press which is a cooperation with a n old-school publisher.

The MySQL cluster study guide  is published by Lulu.com which is an online on-demand publisher.

Lulu.com Cons:
1. The print quality is worse.
2. The paper is less white.
3. The layout is more compact. The margins are really small.

Lulu.com Pros:
1. On-demand print. This will make updated versions possible.
2. The book is smaller














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My MySQL wishlist
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This is my personal whishlist for MySQL.

Please let me know if I'm wrong or if there is a workaround for any of these items.

1. Per user and/or per database quota
Would very useful in setups for shared hosting. This would also prevent one database from bringing down the whole server. Separate tablespaces on different mountpoint can ease the pain, but I consider that a nasty hack.

2. External authentication
I've seen numerous scripts which fetch the authentication info from ldap, a file, another database or some other authentication store. This should be integrated into mysql. The mysql grant tables should be pluggable so it is possible to write a custom authentication plugin. We already have plugable engines and function (UDF) so this shouldn't be that hard is it?

3. Database locator
So you've got hundreds of servers.... and a multitude of databases.










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Good luck, MySQL!
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BusinessWeek reports MySQL continuing with their IPO preparations. As a long-time user (about ten years now), and almost as long-time customer (in many companies, obviously currently and most significantly Sulake and Habbo), I wish you guys the best of luck on that road. Don't lose your sight of the ballgame while doing that -- we need you to continue to do better with the product itself while the distractions of investor communications will be great.

I'm sure we can all name a few nuisances in every software product we use, and I certainly have a few of those of the MySQL database, but what I really admire the guys for is their approach to innovating in the sales and

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What is the Next Big Thing? (longish)
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In a decade, on-demand virtualized utility computing will be an invisible utility, part of the vital infrastructure of the technological economy.

People will mostly have forgotten what an enormous pain in the ass provisioning computation was today. Today, we don't truly feel that pain, because it seems "normal", everyone has to suffer it together.

The situation right now is, if you have a delivery van, you have to make your own gasoline. And you have to hire and pay for your own mechanics. Seems stupid, doesn't it? It's amazing that there are any delivery vans at all …

Think of the internet itself, what it did to telecoms.

Twenty-five years ago, if you wanted a high speed data connection to a computer in San Francisco, it was a pain. You'd have to come up with a pile of money, and wait a couple of months, at best. Hardware would be dedicated and provisioned, and

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10 Newer Entries Showing entries 31 to 40 of 54 10 Older Entries

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