I started translation of Part 3 "Other cases". In this part I mostly describe how wrong settings can lead to misterious errors. First chapter in this part about large amount of data.

Part 3. Other cases.


Chapter 8. Large amount of data.

There are cases when query is just symptom of wrong behavior, but true reason is wrong settings.

One of the cases is too small max_allowed_packet for data sent. MySQL
server variable max_allowed_packet defines maximum possible amount of
data which MySQL server can receive or send. Amount of
max_allowed_packet is specified in bytes.

Error usually looks like:


$mysql51 test <phpconf2009_1.sql

ERROR 1153 (08S01) at line 33: Got a packet …

SugarCRM. Funding for EnterpriseDB and Morphlabs. Even more core. And more

Follow 451 CAOS Links live @caostheory on Twitter and Identi.ca
“Tracking the open source news wires, so you don’t have to.”

Bittersweet
# OStatic asked whether SugarCRM has violated open source principles.

# Larry Augustin clarified SugarCRM’s approach to open source and openness.

# Savio Rodrigues advised anyone considering SugarCRM not to get hung-up on source code availability.

Funding round
# EnterpriseDB has reportedly raised $7.5m of a …

This is short chapter which gives some clue what to do with concurrent transactions.

Chapter 7. Concurrent transactions.

Yet another frequent example of similar problem is "Lock wait timeout
exceeded" error while you use InnoDB tables. Most often running query
SHOW ENGINE INNODB STATUS is enough to find the problem, because it
will show last transactions. But output of this command does not
contain information about all queries in the same transaction, but only
about last one. What to do if SHOW ENGINE INNODB STATUS doesn't provide
all information?

...

 Rest of the chapter is here

This is new part which contains information about what to do if problem is repeatable only when queries run concurrently.

Chapter 6. Locks and deadlocks.

In the last part we discussed how to find cause of the problem in case
if it is always repeatable. But there are cases when problem occurs
only under particular circumstances.

For example, such easy query can run long enough:


mysql> select * from t;

+-----+

| a   |

+-----+

|   0 |

| 256 |

+-----+

2 rows in set (3 min 18.71 sec)


…

There is not much new content this week. Just summary of what was written before.

Summary.

In the summary of this part I'd want to recommend following:

Try to find a query which causes inconsistent behavior

Use log files:

1. 
   
2. General query log
   
3. Log files in your application
   
4. MySQL Proxy or any other suitable proxy
   
5. Others
   

Analyze what is wrong, then solve the problem using your findings

Below I place a list of methods which we studied in the first part.

Method #1: use output operator to output query in exactly same way in which RDBMS gets it. …

Elephants on parade: Hadoop goes mainstream. And more.

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Elephants on parade
# Cloudera launched v3 of its Distribution for Hadoop and released v1 of Cloudera Enterprise.

# Karmasphere released new Professional and Analyst Editions of its Hadoop development and deployment studio.

# Talend announced that its Integration Suite now offers native support for Hadoop.

# Yahoo …

Translation of chapter 5 which describes alternate methods for searching problem query just published. It starts like:

Chapter 5. Alternate methods for finding problem query.

I already wrote about using of general query log requires resources.
Part of the problem can be solved if use new feature of MySQL 5.1:
online logging which allows to turn general query log to on or to off
without stopping the MySQL server.

Unfortunately this doesn't always work: you can have old
version of MySQL server which has not such a feature, general query log
can contain very large amount of information, so you can just miss the
problem in thousands of correct queries, you can have some other own
reason.

But what to do if you can not use general query log?

…

This chapter starts as:

Chapter 4. Miscellaneous.

There are cases when wrong output is just symptom of wrong input made before.

For example, you start to receive wrong data at particular step of the
scenario. After analysis of the SELECT query (or queries) is clear what
queries are correct and return exactly same data which exists in the
table (or tables).

This means wrong data was inserted at the earlier step.

How to know when it happened?

Start from the step of the scenario which exists just before
step which does output, check every query as was described in earlier
chapters. If everything works correctly, examine earlier step, repeat
until you find the error.

This Thursday (June 10th, 14:00 UTC), Darren Cassar will rerun his February 25 presentation of Securich - Security Plugin for MySQL. (Recording of the session failed in February; hopefully it will succeed this time.) According to Darren, the author of the plugin, Securich is an incredibly handy and versatile tool for managing user privileges on MySQL through the use of roles. It basically makes granting and revoking rights a piece of cake, not to mention added security it provides through password expiry and password history, the customization level it permits, the fact that it runs on any MySQL 5.0 or later and it's easily deployable on any official MySQL binary, platform independent.
More information here: …

This Thursday (June 10th, 14:00 UTC), Darren Cassar will rerun his February 25 presentation of Securich - Security Plugin for MySQL. (Recording of the session failed in February; hopefully it will succeed this time.) According to Darren, the author of the plugin, Securich is an incredibly handy and versatile tool for managing user privileges on MySQL through the use of roles. It basically makes granting and revoking rights a piece of cake, not to mention added security it provides through password expiry and password history, the customization level it permits, the fact that it runs on any MySQL 5.0 or later and it's easily deployable on any official MySQL binary, platform independent.
More information here: …