In some situation (as described below in “how to repeat”) the table_rows column
in the information_schema.tables table is not computed correctly.
The problem arise only for tables included in a merge table.

It seems that if you issue a select statement on a “merged table” the following
insert statement does not update the metadata table_rows.

How-to-repeat

First of all let’s try the example showing the expected behavior


mysql> create table t1 (a int);
Query OK, 0 rows affected (0.00 sec)



mysql> create table t2 (a int);
Query OK, 0 rows affected (0.01 sec)



mysql> create table t (a int) engine=merge union=(t1,t2) insert_method=last;
Query OK, 0 rows affected (0.01 sec)



mysql> insert into t values(1),(2);
Query OK, 2 rows …

I already wrote in the blog as well mentioned in presentation there is often a choice you have to make between having prefix index - which can be significantly smaller in size and having index being covering index, which means query can be executed using only data from the index without reading the row itself.

Today I had a chance to do couple of experiments to see when exactly it works or does not work:

PLAIN TEXT SQL:

1. CREATE TABLE `t` (
2.   `i` int(11) DEFAULT NULL,
3.   `j` char(10) DEFAULT NULL,
4.   `k` int(11) DEFAULT NULL,
5.   KEY `i` (`i`,`j`(5),`k`)
6. ) ENGINE=MyISAM

Now lets see if index can be used as covering index if it has some key parts which are prefixes:

PLAIN TEXT SQL:

1. mysql> EXPLAIN SELECT k FROM t WHERE i=5 \G
…

My blogging hasn't been so active lately. Mostly due to that I've been busy on
other things. One of the things that have kept me busy the last few months
is a project which I highly enjoy. I've been performing a benchmark study
of MySQL Cluster using Dolphin SuperSockets. Performance is one of my
favourite topics and a parallel database like MySQL Cluster has a wide array
of performance challenges that makes it very interesting to optimize it.

I will present the results in two webinars on the 30th Nov and 13 dec. The
webinars will also provide some input to the features in Dolphin
SuperSockets and MySQL Cluster that enables high performance and
real-time characteristics. With these changes to MySQL Cluster and using
the Dolphin SuperSockets MySQL Cluster becomes even more adapted for
all types of real-time applications.
See:
…

As mentioned in an earlier post the partitioning in 5.1 has reached a level of
stability so that it can now be put to some heavier test. To spread further
insights of the new partitioning feature I'll deliver two webinars next week
and the week after that (29 nov and 5 Dec).

You'll find a reference to both from the MySQL Home Page.
http://www.mysql.com/

The first one will give an introduction to partitioning in MySQL and
describe the variants of partitioning that will be supported, which
management variants that are possible and so forth.

The second webinar is a follow-up that will do some repetition to
ensure it can be viewed stand-alone but will mainly dive a little
deeper into various areas of partitioning amongst other how it
relates to MySQL Cluster.

David Kaefer, the director of business development for intellectual property and licensing at Microsoft, is on the record as saying a rather curious thing:

We've been very clear from the outset, and the financial realities of the deal underscore this, that Novell's patents have value. One need only go back to the late 90s with Novell's leadership in the directory space to recognize the benefits of much of the research and development that they conducted at that time.I'm sure this is true; at least, I'm sure it's true (in fact, I know so) that Novell's patent portfolio is significant. Not nearly as extensive as Microsoft's, but significant in its own right.

But let's assume David is telling the truth. If so, then Microsoft, not Novell, …

Ubuntu Wins Most User Friendly Linux Distribution Award, Canonical (Press Release)

IBM sees Novell/MS deal benefiting Linux, Linux-Watch, Steven J. Vaughan-Nichols (Article)

Good karma for Red Hat, iTWire, Sam Varghese (Article)

Microsoft-Novell Honeymoon Ends, LinuxInsider, Jay Lyman (Article)

Enterprise Open Source, Line56 E-Business Blog, Simon Phipps (Blog)

Patent peace for our time?, …

BuilderAU released a recent article titled Developer skills outlook 2007: What’s hot for employers. There are a few things to take away from the article, that seem to apply not only to Australia, but elsewhere.

“The biggest issue that we see generally speaking is that the overall skill level of the developers is not where it needs to be,” said Jeff Pope, Asia Pacific vice president for Agitar Software.

The general idea of skills shortage. And its not that there’s a shortage of people in the market, the universities and TAFEs are churning them out by the dozen; its the lack of highly-skilled people. So where should aspiring IT people aim to spend their passion and hone their talents and ambitions in 2007?

It would seem that it’s in the Java and C# …

I often find links to my own stuff when googling for one thing or another - particularly when googling for ODBC stuff. Today I found an old Linux Journal article I did 7 years ago. I recall being upset about the fact that they printed the draft - but it seems to be mostly fine.

It makes me realize how fast time zips by but also how far ODBC on non-Windows platforms has come since those days. We can now deliver a good MySQL Connector/ODBC solution on all platforms where the MySQL client library is available - and that is a dizzying list of platforms!

I think nobody would argue today, that search engines are most import sites in todays Internet. There are lots of information sources in the Net today, and every day they are generating lots of useful content. One of major parts of this content is generated by forums aka bulletin boards. But Google - most popular search engine is not to efficient on this side of search - if you try to find something using Google, you can find information on some public forum, but Google SERP is designed for generic pages search and search results will be not so clear. That is why more specialized search engines are so popular. Technorati, Google and Yahoo blog search engines, etc are really popular today.

Just few days ago new search engine was released. Its name is Board Reader. IMHO, its major advantage of this search engine is specialization on search by …

Is it possible to run Stored Procedures on MySQL 4.x? Yes and no - of course the feature is not available directly in MySQL 4.x, but if you have a MySQL 5.x server with the FEDERATED Storage Engine available, it's no big deal to accomplish that.

Here's how it works - we start with this on a MySQL 4.x server:

mysql> SELECT version();
+-----------+
| version() |
+-----------+
| 4.0.18-nt |
+-----------+
1 row in set (0.03 sec)

mysql> SHOW CREATE TABLE tt \G
*************************** 1. row ***************************
       Table: tt
Create Table: CREATE TABLE `tt` (
  `id` int(10) unsigned NOT NULL auto_increment,
  `val` int(10) unsigned NOT NULL default '0',
  `ts` timestamp(14) NOT NULL,
  PRIMARY KEY  (`id`)
) TYPE=MyISAM
1 row in set (0.03 sec)

mysql> SELECT * FROM tt;
Empty set (0.03 sec)

The next step …