I was reading some points on a Blog post today here. I didn’t see it via Planet MySQL but via a Google Alert.

The post has several good beginner points on MySQL Performance, but included the point “Literal current date is better than using the CURRENT_DATE() function because literals will use the query cache but functions won’t.”

How true, I must admit I’d not considered this in reviewing code for sites that use the Query Cache heavily. Non deterministic functions invalid use of the Query Cache (Except for recent Bug #29053 which is also an interesting read. Note to self, read the new bugs more often when free time permits). Back on point.

So if you have a query like “Select the news for today” and use CURDATE(), it will not be stored in the Query Cache, yet if your application code determines the current date and passes “Select the news for 2007-06-26″ for example it will.

Sometimes the simple things are easy to forget, or not have thought about in this case for me.

I’ve been able to steal some more time to work on my script following My ‘hourly’ MySQL monitor script Version 0.03 almost a month ago.

The purpose of this script is simple. Create an hourly ‘cron’ job that records and monitors information against the OS and MySQL Server. This is most helpful when environments simply don’t have any monitoring in place. I’ve found it very productive when running a benchmark on site to simply enable for an hour. An amount of analysis is required, but I at least have a baseline of data collection. That is the first goal.

So hourly.0.05.tar.gz is taking some shape, and has the following new features:

• Provide configurable flag to enable/disable OS and MySQL tests
• Added MYSQL_SID support, allowing for running MySQL tests against multiple instances on a single server
• Added configurable mysql.conf support, again supporting multiple server instances
• Revised file name standards, again to support multiple server instances
• Added additional error checking for correct MySQL Configuration and operational environment
• Corrected file pathing of dependent files

My next step now is to provide some simple analysis, I’ll be starting with Statpack Version 2 by colleague Mark Leith.

I didn’t know you could actually do this before addressing this problem in a benchmark using 5.0.36.

MySQL allows you to update two tables with a single UPDATE statement. I knew you could reference two tables in an UPDATE statement but not update both. However when working with a client after benchmarking I observed a large number of Created_tmp_disk_tables via SHOW GLOBAL STATUS and found that this query was the offending query only for certain circumstances. Understanding took a little longer.

schema.sql

DROP TABLE IF EXISTS a;
CREATE TABLE a(
id  INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
i   INT UNSIGNED NOT NULL,
c   CHAR(1) NOT NULL)
ENGINE=INNODB;
DROP TABLE IF EXISTS b;
CREATE TABLE b(
id  INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
i   INT UNSIGNED NOT NULL,
c   CHAR(1) NOT NULL,
t   TEXT NOT NULL)
ENGINE=INNODB;

data.sql

INSERT INTO a VALUES(1,1,'a');
INSERT INTO a VALUES(2,2,'b');
INSERT INTO a VALUES(3,3,'c');
INSERT INTO a VALUES(4,4,'d');
INSERT INTO b VALUES(1,1,'a',REPEAT('The quick brown fox jumped over the lazy dog',100));
INSERT INTO b VALUES(2,2,'b',REPEAT('The quick brown fox jumped over the lazy dog',200));
INSERT INTO b VALUES(3,3,'c',REPEAT('The quick brown fox jumped over the lazy dog',300));
INSERT INTO b VALUES(4,4,'d',REPEAT('The quick brown fox jumped over the lazy dog',400));

test.sql

SHOW SESSION STATUS LIKE '%tmp%tables';
SHOW SESSION STATUS LIKE '%tmp%tables';
UPDATE a,b SET a.i = 10, a.c = 'x', b.i = 20 WHERE a.id = b.id and a.id=1;
SHOW SESSION STATUS LIKE '%tmp%tables';
UPDATE a,b SET a.i = 10, a.c = 'x', b.i = 20,b.t=REPEAT('b',5000) WHERE a.id = b.id and a.id=3;
SHOW SESSION STATUS LIKE '%tmp%tables';
UPDATE b SET t = REPEAT('a',5000) WHERE b.id=2;
SHOW SESSION STATUS LIKE '%tmp%tables';

Output

The following output shows the following.

1. Impact of a SHOW SESSION STATUS increments Created_tmp_tables
2. A two table update increments Created_tmp_tables
3. A two table update including a text field increments Created_tmp_tables and Created_tmp_disk_tables
4. A single table update with the text field increments Created_tmp_tables

So the culprit was the combination of a two table update and a TEXT field.

mysql> source test.sql
--------------
SHOW SESSION STATUS LIKE '%tmp%tables'
--------------

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 0     |
| Created_tmp_tables      | 3     |
+-------------------------+-------+
2 rows in set (0.00 sec)

--------------
SHOW SESSION STATUS LIKE '%tmp%tables'
--------------

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 0     |
| Created_tmp_tables      | 4     |
+-------------------------+-------+
2 rows in set (0.00 sec)

--------------
UPDATE a,b SET a.i = 10, a.c = 'x', b.i = 20 WHERE a.id = b.id and a.id=1
--------------

Query OK, 2 rows affected (0.02 sec)
Rows matched: 2  Changed: 2  Warnings: 0

--------------
SHOW SESSION STATUS LIKE '%tmp%tables'
--------------

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 0     |
| Created_tmp_tables      | 6     |
+-------------------------+-------+
2 rows in set (0.00 sec)

--------------
UPDATE a,b SET a.i = 10, a.c = 'x', b.i = 20,b.t=REPEAT('b',5000) WHERE a.id = b.id and a.id=3
--------------

Query OK, 2 rows affected (0.00 sec)
Rows matched: 2  Changed: 2  Warnings: 0

--------------
SHOW SESSION STATUS LIKE '%tmp%tables'
--------------

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 1     |
| Created_tmp_tables      | 8     |
+-------------------------+-------+
2 rows in set (0.00 sec)

--------------
UPDATE b SET t = REPEAT('a',5000) WHERE b.id=2
--------------

Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

--------------
SHOW SESSION STATUS LIKE '%tmp%tables'
--------------

+-------------------------+-------+
| Variable_name           | Value |
+-------------------------+-------+
| Created_tmp_disk_tables | 1     |
| Created_tmp_tables      | 9     |
+-------------------------+-------+
2 rows in set (0.00 sec)

First it was the SlashDot effect, then it was the Digg effect, now it’s the Facebook effect. I have a friend at Facebook and he was talking about the effect of the Facebook Platform API that was released a few weeks ago. Sites were now struggling to cope with the effect of massive amounts of new traffic, ensuring that experienced MySQL Consultants will have plenty of scale out opportunities.

Here is an abstract from an article I read recently. Analyzing the Facebook Platform, three weeks in

Translation: unless you already have, or are prepared to quickly procure, a 100-500+ server infrastructure and everything associated with it — networking gear, storage gear, ISP interconnetions, monitoring systems, firewalls, load balancers, provisioning systems, etc. — and a killer operations team, launching a successful Facebook application may well be a self-defeating proposition.

This is a “success kills” scenario — the good news is you’re successful, the bad news is you’re flat on your back from what amounts to a self-inflicted denial of service attack, unless you have the money and time and knowledge to tackle the resulting scale challenges.

This comes from the success of iLike. Some more reading references are Crazy love when startup iLike hits pay dirt and Holy cow… 6mm users and growing 300k/day!. Wow!

You can’t buy viral marketing with this type of traffic growth figures. Given the current MySQL 12 Days of Scale-out and recent experiences where clients are seeking HA & scale-out solutions but have not architectured present systems to manage any level of scale-out via the MySQL proven techniques of replication and sharding.

It’s an important lesson that any organization wanting to develop a successful web site needs to ensure the architecture is designed with massive scale-out in mind from the beginning. This means starting with your application supporting partitioning of your data (both vertically and horizontally), and supporting replication, including the possibility of lag with MySQL Replication slaves.

You see on a lot of larger Web 2.0 sites these days after saving data, a message like “Your information will be available momentarily” or a message of this nature and the data saved not automatically displayed. This is a clear means of supporting lag, even if only for a few milliseconds. This is just the first of many steps in application design managing scale-out architectures.

I was reading only last week the notes from Wikipedia: Site Internals, Configuration and Code Examples, and Management Issues Tutorial by Domas Mituzas at the recent 2007 MySQL Conference. I didn’t attend this session, like a lot of sessions too much good stuff at the same time.

It’s obviously taken a while to catch up on my reading, but with the present MySQL 12 days of Scale-Out I thought I’ll complete my notes for all to see.

If you have never used Wikipedia well, why are you reading this, you should spend an hour there now. Alexa places Wikipedia in one of the top 10 visited sites on the Internet.

Wikipedia runs on the LAMP stack, powered by the MySQL database. Nothing new here, but how Wikipedia scales is. Some of the interesting points involved how a “Content Delivery Network” was build with components including Squid, Lighttpd, Memcached, LVS to improve caching. Appropriate caching is an important component to a successful scale-out infrastructure. An interesting quote however:

The common mistake is to believe that database is too slow and everything in it has to becached somewhere else. In scaled out environments reads are very efficient, and difference of time between efficient MySQL query and memcached request is negligible – both may execute in less than 1ms usually).
Sometimes memcached request may be more expensive than database query simply because it has to establish connection to a server, whereas database connection is usually
open.

Wikipedia has a developed an application Load Balancer. This offers a flexibility in efficient database use and is critical to any scale-out infrastructure. Combined with a good Database API and items such as the Pager class, allows you to write efficient index-based offsets pager (instead of ugly LIMIT 50 OFFSET 10000) syntax for example.

The main ideology in operating database servers is RAIS: – Redundant Array of Inexpensive/Independent/Instable[sic] Servers

• RAID0. Seems to provide additional performance/space. Having half of that capacity with an idea that a failure will degrade performance even more doesn’t sound like an efficient idea. Also, we do notice disk problems earlier. This disk configuration should be probably called AID, instead of RAID0.
• innodb_flush_log_at_trx_commit=0, tempted to do innodb_flush_method=nosync. If a server crashes for any reason, there’s not much need to look at its data consistency. Usually that server will need hardware repairs anyway. InnoDB transaction recovery would take half an hour or more. Failing over to another server will usually be much faster. In case of master failure, last properly replicated event is last event for whole environment. No ‘last transaction contains millions’ worries makes the management of such environment much easier – an idea often forgotten by web applications people.

The thing I found interesting in the RAIS mysql-node configuration was slave-skip-errors=0,1213,1158,1053,1007,1062

However, the greatest tip is “All database interaction is optimized around MySQL’s methods of reading the data.” This includes:

• Every query must have appropriate index for reads…
• Every query result should be sorted by index, not by filesorts. This means strict and predictable path of data access…
• Some fat-big-tables have extended covering indexing just on particular nodes…
• Queries prone to hit multiversioning troubles have to be rewritten accordingly…

Wikipedia is also clever in it’s sharding. A means to implement vertical and horizontal partition of data via the application for optimal scale-out. This comes down to designing your application correct from the start. Wikipedia considers it’s partition via:

• data segments
• tasks
• time

HiveDB (not used by wikipedia) is open source framework for horizontally partitioning MySQL systems. Well worth reviewing.

Wikipedia also makes use of compression. This works when your data can be compressed well like text. This improves performance, however analysis on other projects have shown this does place a CPU impact on the server so it is important to monitor and use appropriately.

Another clever approach is to move searching to tools more appropriate for this task, in this case Lucene. As with any scale-out it is important to leverage the power of appropriate tools for maximum benefit.

I have only summarized Domas’ notes. It’s well worth a detailed read.

I was asked recently to confirm a consistent state of data in a non-transactional MySQL table after a failing statement updating multiple rows did not complete successfully.

Hmmm, this is what I did.

• Created a MEMORY table
• Populated with some data, and a Primary Key
• Updated the Primary Key so that it failed with a Duplicate Key Error after updating only half the rows
• Confirmed that the rows that were updated, were, and the rows that were not updated, were not

DROP TABLE IF EXISTS mem1;
CREATE TABLE mem1(
i1  INT UNSIGNED NOT NULL PRIMARY KEY,
c1 CHAR(10) NOT NULL,
dt TIMESTAMP)
ENGINE=MEMORY;

INSERT INTO mem1(i1,c1) VALUES (1,'a'), (2,'b'), (3,'c'), (4,'d'), (5,'e');
SELECT * FROM mem1;
+----+----+---------------------+
| i1 | c1 | dt                  |
+----+----+---------------------+
|  1 | a  | 2007-06-14 17:26:29 |
|  2 | b  | 2007-06-14 17:26:29 |
|  3 | c  | 2007-06-14 17:26:29 |
|  4 | d  | 2007-06-14 17:26:29 |
|  5 | e  | 2007-06-14 17:26:29 |
+----+----+---------------------+
5 rows in set (0.00 sec)

UPDATE mem1 SET i1 = 9 - i1 - SLEEP(1), c1='x' ORDER BY i1;
ERROR 1062 (23000): Duplicate entry '5' for key 1
SELECT * FROM mem1;
+----+----+---------------------+
| i1 | c1 | dt                  |
+----+----+---------------------+
|  8 | x  | 2007-06-14 17:29:05 |
|  7 | x  | 2007-06-14 17:29:05 |
|  6 | x  | 2007-06-14 17:29:05 |
|  4 | d  | 2007-06-14 17:28:36 |
|  5 | e  | 2007-06-14 17:28:36 |
+----+----+---------------------+
5 rows in set (0.00 sec)

While I was also hoping for the TIMESTAMP column to reflect when the row was modified, it was when the statement was executed.

This test did however prove the requirements. Simple when you think about it, but it took a few minutes to think about it the first time.

I recently saw the Planet MySQL post Five months with MySQL Cluster by Brian Moon.

Thought I’d add my 5 cents worth (Australian’s don’t have 1 cent coins any more to make 2 cents worth)

Firstly, it’s great you wrote about your experiences in moving to MySQL Cluster. I think more people should.

Joins

“We used a lot of joins. We learned (later) that joins in the cluster are not a good idea.”

MySQL Cluster’s number one strength is Primary Key Lookups, it’s very good you learned that joins (especially say 5-6-7 table joins) are not a good idea, it is not a strength, and certainly not scalable to thousands of queries per second.

Rewrite

“We rewrote our application (basically, our public web site) to use the new cluster and its new table design.”

It’s great you acknowledged that you had to rewrite your application. I’m sure the attitude of people in the industry is: We need more HA, MySQL offers MySQL Cluster as a HA 5x9s solution, let’s just put out existing application on Cluster. This simply does not provide the results people think, and could in theory result in disaster, particularly when choosing H/W, see next point.

I would expand on a few cases of what you re-wrote, this level of education will help educate the masses.

Hardware

“Six new Dell dual-core, dual processor Opterons with a lot of memory”.

First, MySQL Cluster is an in-memory database, so lots of memory is essential. Second, Data Nodes are a single threaded process, so even with 4 cores your H/W will be underutilized as data nodes.

If an organization wants to say get two 4 CPU Dual Core machines (that’s 2×8 cores per machine), it’s impractical to use as Data Nodes. Far greater performance, reliability and scalability is obtained by having 8×2 core machines. The issue then becomes power consumption and rack space, this is what hurts MySQL Cluster. It’s important to remember MySQL Cluster was designed to run on low commodity hardware, and a lot of it.

“So, we configured the cluster with 4 replicas.”

Interesting. You don’t see many references to more then the default, documented and accepted 2 replicas.

Administration

“MySQL Cluster is a whole new animal.”

Yes it is, an ALL DUMP 1000 for example, and then having to parse log files for the “right” strings needs to be improved for example just to determine memory utilization. You may also want to check out ndbtop. I managed to get an earlier version working, but never really had the time to delve more. Monty also may have some admin stuff of interest buried within his NDB Connectors work.

Conclusions

“What a moron!”

Far from it, I hope your article helps in the education of MySQL Cluster more to the community. I’m certainly going to reference my responses to your article as “key considerations” in considering MySQL Cluster for existing applications.

I would add that with MySQL Cluster you require all equipment to be within a LAN, even the same switch. This is important, MySQL Cluster does not work in a WAN situation. I’ve seen an example H/W provided for a trial Cluster with some machines in a West Coast data center, and some in an East Coast data center.

You also can’t have a lag slave for example as in a Master/Slave environment.

You didn’t mention any specific sizes for data, I’d be interested to know, particularly growth and how you will manage that?
You also didn’t mention anything about Disk? MySQL Cluster may be an in-memory database but it does a lot of disk work, and having appropriate disk is important. People overlook that.
You didn’t mention anything about timings? Like how does backups for example compare now to previously.
You didn’t mention version? 5.1 (not GA) is significant improvement in memory utilization due to true varchar support, saving a lot of memory, but as I said not yet production software.

Ok, so I knew about innodb_table_monitor and innodb_tablespace_monitor. I’ve tried them before, looked at the output and given up, partly because it didn’t serve the purpose I wanted it to at the time, and also because it’s format was a little cryptic.

What I didn’t know was there are actually 4 monitors via this “create table functionality”. You can also do innodb_monitor which is the same as SHOW INNODB STATUS, and you can also do innodb_lock_monitor .

Another thing I didn’t know is that these commands don’t send the output just once, it’s on a timer. I’ve found the timers to be different. For innodb_monitor you get every 15 sec, as well as a nice line given time of averages which seems to always say 16 seconds.

=====================================
070601 15:11:25 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 16 seconds

innodb_table_monitor was in this case 65 seconds??

===========================================
070601 15:13:33 INNODB TABLE MONITOR OUTPUT
===========================================
 ...

===========================================
070601 15:14:37 INNODB TABLE MONITOR OUTPUT
===========================================

The fact it goes to the MySQL error log is annoying, rather then a log for Innodb Monitoring. It’s much easier to script when you know the content coming into a file and can control it, with the MySQL error log you can’t.

More info at SHOW ENGINE INNODB STATUS and the InnoDB Monitors.

So you have to read the fine print in the MySQL Manual to get these things. If you also read the manual page to completion, which I did after I wrote this initial post you find yet another option innodb_status_file. If this is set for the server, it writes the output of SHOW ENGINE INNODB STATUS to a file every 15 seconds. What about the other outputs to file? Seems a need to be consistent here.

Things to ponder more.

Now were are all those useful tools that parse this output?
Is this output worth parsing and monitoring at any regularity?

Updated: 06/09

Two additional references that help in the understanding of these monitors are:

• SHOW INNODB STATUS walk through – July 2006
• InnoDB Table and Tablespace Monitors – Jan 2009

Log Buffer #47: a Carnival of the Vanities for DBAs
June 1st, 2007 – by Ronald Bradford

Welcome to the 47^th edition of Log Buffer, the weekly review of database blogs. No time to wait, lets read more about this week’s database blogging activities.

The PostgreSQL Conference for Users and Developers wrapped up this week and Peter Eisentraut gives us a review including the lightning talks and wrap-up session with a charity auction in PGCon Day 4. Meanwhile Alex Gorbachev is at Miracle Scotland Database Forum – Day One, sounds like from his post there is a lot of drinking and tasting going on.

Tim Hall in Schema Owners and Application Users… starts with “I was trying to explain to a colleague the concept of using application users, rather than logging directly into the schema owner.” As he mentions, it’s an introductory topic however his article gives us a detailed discussion of implementation.

An OTN blog consolidates a number of announcements for Oracle, PHP and OPAL in it’s concise publication New PHP Doc and Software. Plenty of reading links here.

Paul Moen of Pythian covers an important step in Oracle: Standby Automatic File Management follows on from his earlier posts in creating a standby database.

Roland Bouman in MySQL User Defined Function Repository has made an effort to build a central repository of the varied UDF’s that exist to extend MySQL SQL Function syntax. His follow up article The MySQL UDF Repository: lib_mysqludf_sys shows just how dangerous these can really be.

Partitioning, a key new feature in MySQL 5.1 can be incorrectly used as Sergey Petrunia has described in Partition pruning tip: Use comparisons of column, not of partitioning function value. While 5.1 is not GA yet, and maybe not for some time Kevin Burton was quick to comment about software functionality about to be deployed with this new functionality. Of course partitioning in MySQL is free, in Oracle it is not as Mathias describes in Rant about partitioning licensing. Not only do you have to purchase the top of the line Enterprise Edition at 40K, you have to purchase an additional option on top of that. I didn’t know that.

Peter Zaitsev of the MySQL Performance Blog discusses Predicting how long data load would take. This is a very common problem particularly in a direct changeover of a production system to MySQL, and as with Peters example of loading 1TB, this is no longer an uncommon problem with MySQL.

Jag Singh from Optimize Data Warehouse uses a practical approach in Data type validation using regular expressions with a procedural language before data loading into a database, or performed within a database. It’s important we don’t lose site that some things are best done not in the database.

Slashdot starts a flame war with aptly titled 8 Reasons Not To Use MySQL (And 5 To Adopt It) with a reference between Five Compelling Reasons to Use MySQL and Eight Sound Reasons Not to Use MySQL, both published by CIO magazine on the same day. MySQL Performance Blog, and Curt Monash were quick to respond with MySQL – to use or not to use and Whether or not to use MySQL respectively.

Q&A Webinar Part 4 – MySQL Cluster by Ivan Zoratti gives us 33 points of reference with MySQL Cluster. Being involved with MySQL Cluster, it’s interesting to read the types of questions people are asking. Following up, Jonathan Miller a seasoned veteran with MySQL Cluster shows in Just when you think you know something that even the experts can be stretched with the new MySQL Cluster Certification Exam. Likewise I was surprised when I passed the exam myself recently of it’s complexity.

Andy Campbell in his blog Oracle Stuff I Should Have Known demonstrates he has too much spare time on his hand in understanding terminal colors in a novel but interesting Adding some colour to SQL*Plus. Would have looked better with some blue!

One of the features I promote in MySQL, and that exists in other RDBMS’, but Oracle does not have is native Multirow Inserts. Robert Vollman however provides Oracle’s two verbose alternatives. Only knew about one of them myself. Still they are far from the simplicity other database products have.

Brian Duff of DuffBuff writes If I had five Oracle wishes, they would be…. We all have wish lists and Brian writes, “I was thinking about things in the Oracle-sphere that I’d love to see happen over the next few years”. I won’t spoil his wish list, I think point 4 is a good one.

Using the OUTPUT and OUTPUT INTO clauses in SQL Server 2005 describes the new features for retrieving values that were just inserted/updated/deleted by a DML statement. Vardecimal Storage Format in SP2 discusses another new feature in SQL Server 2005, the new Vardecimal format. The caveat being that this functionality is restricted to the Enterprise and Developer Editions. One using SQL Server should also know about the Swiss-knife features in SQL Server to help you.

Things to take care before installing SQL Server 2005 on Vista operating system or Windows Server 2008?. Nothing more to say here, perhaps you need to read if your a SQL Server user.

Data Geek Gal Beth touches on one of my pet peeves in Data Quality: As Meets the Needs of an Organization. If data has a structure, appropriate rules should be put in place to ensure this is maintained in the database. You will forever be doing data cleansing if you simply bother to consider this basic step later. Developers should really learn to be smarter in this area. One point not discussed is, “Where are the validation rules applied, the application or the database?”

View Larger Image

I’m not sure if a Log Buffer has had any images before, but I recently stopped at the Oracle HQ in Redwood city to snap this photograph. The irony of the experience not portrayed within the photograph was I worked for Oracle Corporation in the 1990’s but never visited the HQ, and while I was out taking this photo I was wearing a MySQL shirt. (No honking by any peak hour Oracle workers).

That’s it for this week, until next week. Clocks ticking Frank!

NOTE: Problems presently exist, I’m seeking the expert help of the community and Perl Gurus

I have the need to do some quick benchmarking, I use MyBench as it’s effective in being able to plug in a query, some randomness and 2 minutes later (with a correctly configured Perl/MySQL environment) you have multi-threaded load testing.

However, when the environment you are on is not configured, and you only know the basics for Perl Operation and Installation, (code is just code, that’s the easy part) and the box is not accessible to the outside world say for cpan, it gets more complicated. I’ve attempted to install and configure DBI, DBD::mysql and Time::HiRes but without success.

DBI
DBI was straightforward, a download, make, install worked without issue. a make install was performed.

DBD:mysql
DBD::mysql didn’t need an compile, mysql.pm already existed and make said it was all up to date. However then running mybench gave the first error.


failed: Can't locate DBD/mysql.pm in @INC


Ok, so it wasn’t installed as ‘root’. Some small Perl Pathing.


PERL5LIB=~/DBD-mysql-4.004/lib;export PERL5LIB


Let to the next error:


failed: Can't locate loadable object for module DBD::mysql in @INC (@INC


Hmmm, a little more complicated. So going back to the compiling part, I realized I could force compile it, and this also confirmed one possible issue, the libmysqlclient library.


perl Makefile.PL
I will use the following settings for compiling and testing:
cflags (mysql_config) = -I/path/to/mysql/include
embedded (mysql_config) =
libs (mysql_config) = -L/path/to/mysql/lib -lmysqlclient -lz -lcrypt -lnsl -lm
..


Both the mysql.h and libmysqlclient software correctly located and valid, but still no luck.

Moving in parallel I then managed a SA that could install the rpm’s (being RHEL). Problem is, MySQL is not installed via RPM, so the only possible means of installing DBD::mysql is to force no dependencies. This did not prove successful be added clues to the problem.


failed: Can't load '/usr/lib64/perl5/vendor_perl/5.8.5/x86_64-linux-thread-multi/auto/DBD/mysql/mysql.so' for module DBD::mysql: libmysqlclient.so.14: cannot open shared object file: No such file or directory at /usr/lib64/perl5/5.8.5/x86_64-linux-thread-multi/DynaLoader.pm line 230.


So it used the installed DBD::mysql, and it couldn’t find the expected library path. This gives some confident that perhaps the earlier version is right, and that some other dependancy is missing.

I’ve not found any good resource to work though this online in my environmental situation, but surely this is pain that somebody else has experienced.

Thanks for those friends that have already contributed small parts to getting someway here, however it just ain’t working, and I need it to just work.

Any input appreciated.

I learned an extremely valuable lesson today on a client site. It’s important that users of MySQL read the right version of the manual for the product they are using. It’s very easy to just goto http://dev.mysql.com/doc/ which is what I type in directly and browser the manual. While the MySQL Manual has separate sections for 4.x, 5.0, 5.1 etc, the 5.0 Manual for example reflects the most current version of MySQL 5.0. You may not be running the most current version, infact most production systems rarely run the current version.

My specific case was with Connector/J (JDBC) Reference of 5.0.4. The manual pages reflects the new 5.0.5 or todays’ 5.0.6 release and a particular default is now a different value. With Connector/J the docs are bundled with the version. The MySQL Community Server product does not bundle the manual, and I don’t know where to view instances of the MySQL manual for each specific dot release!