In MySQL a big portion of the problems you’re facing is different replication delays so there’s no surprise this is one of the most common interview questions on DBA interviews and I still found people having problems with explaining what they would do in a certain situation. This is why I decided to write a bit about the subject.

1. IO

99% of times the reason is IO. The slave cannot keep up with the amount of writes it gets from the binary logs while in parallel it has to return results of queries as well. In spite of the common belief in MySQL it’s much easier to saturate the disk subsystem (even a raid 10 with 8 SAS disk and cache) than the network.

In this situation all you can do is try to remove some pressure from the slaves.

One way to do this is setting innodb_flush_log_at_trx_commit  to 2 if it used to be 1. Usually this is enough.

SQLAchemy has support for MySQL Connector/Python for a while now. Here is a little HOWTO showing how install both, and setup a database engine.

There are multiple ways of installing both projects, but here is the simplest using pip, whatever platform you use:

shell> pip install SQLAlchemy
shell> pip install mysql-connector-python 

Start your SQLAlchemy engines using a URL pointing to Connector/Python. Note the connect_args argument which passes extra connection arguments to Connector/Python. In the following example we set the MySQL session variable time_zone …

Fetching data from a database to then get it into an Excel spreadsheet to do analysis, reporting, transforming, sharing, etc. is a very common task among users. This task can be accomplished in several different ways and with different tools getting the same result; but users may find the process rather complicated, too technical and lengthy. With MySQL for Excel the task of importing data from a MySQL database to an Excel spreadsheet becomes an easy one and accessible to all types of users.  Here is a quick guide describing how to import data to Excel using MySQL for Excel.

It is possible with MySQL Connector/Python to define your own cursor classes. A very good use case is to return rows as dictionary instead of tuples. This post shows how to do this using MySQL Connector/Python v1.0 and is an update for an older blog entry.

In the example below we are subclassing the MySQLCursor class to create a new class called MySQLCursorDict. We change the _row_to_python() method to return a dictionary instead of a tuple. The keys of the dictionary will be (unicode) column names.

from pprint import pprint
import mysql.connector

class MySQLCursorDict(mysql.connector.cursor.MySQLCursor):
    def _row_to_python(self, rowdata, desc=None):
        row = super(MySQLCursorDict, self)._row_to_python(rowdata, desc)
        if …

Read the original article at Consulting essentials: Building your business

In the last two posts on how to build a successful consulting business I shared advice and tips on closing deals and managing and completing your engagements.

This post will look at where to focus your efforts in order to sustain your consulting business, and build skills.

Focus on your subject matter expertise

Being a subject matter expert takes years of education, and professional experience to build. It’s your most valuable asset. Build it, and use it. This is not to say there isn’t great value in …

Background Knowledge

I using PHP v5.3.3-7 PDO running a MySQL v14.14 Distrib 5.1.49 on Debian v6.0.4 64-bit and executing a SQL load data infile statement.

I received “PHP Warning: PDOStatement::execute(): SQLSTATE[HY000]: General error: 126 Incorrect key file for table ‘/tmp/#sql_66f_0.MYI’; try to repair it”. My database table in this instance is using the storage engine of InnoDB and therefore one can not use the “repair table”.

From my experience I’ve found that this error can mean one of two issues however I have not found information from MySQL confirming this.

Solution – Repair Table

The error message may mean the database table is corrupted and requires a repair.

1. Run repair table on the …

Background Knowledge

The progress of a task in TaskFreak! is shown as a percentage value and is not exactly visually appealing to quickly spot the progress. With a few minor alterations we can show the percentage completed bar that fills as the task progresses and a gradient bar indicating the progress along with the percentage value.

This solution was posted by Searcher at Re: Taskfreak Customizing Status.

Solution

1. Edit at line #268 as shown below.
   Cod Before

   268	<th width="<?php echo FRK_STATUS_LEVELS * 2; ?>%" onclick="freak_sort('statusKey')" colspan="< ?php echo FRK_STATUS_LEVELS ?>" class="sortable">< ?php echo (FRK_STATUS_LEVELS == …

MySQL Cluster is, without doubt, the most interesting MySQL product Oracle offers to the people out there. It’s the flagship, the holy grail, based on the knowledge and technology developed doing our well known MySQL Server. I’m not going to go through why MySQL Cluster is so great, that you can find anywhere. I’m going [...]

This post explains how to debug MySQL Cluster 7.1, installed using the RPM packages, using gdb on a Linux box (Red Hat, Oracle Enterprise Linux, CentOS, ..).

When a data node crashes lots of information goes into the error log, trace files and out log. However, it makes sometimes sense when you can repeat the crash, to run the data node in debug mode, or using gdb.

First, using RPMs and a Linux distribution, make sure you have the ‘debuginfo’ package installed. For example, for Red Hat or Oracle Enterprise Linux on a 64-bit machine, this package would be called: MySQL-Cluster-gpl-debuginfo-7.1.15-1.rhel5.x86_64.rpm .

Create a file with the following commands, we will name it ‘ndbd.gdb’:

set pagination off
set logging overwrite on
set logging file …

There is a log file called ndb_<NodeID>_out.log created by the MySQL Cluster data nodes which can become quite big overtime. There is, unlike the cluster logs created by the management nodes, no rotation build in. So you have to revert to the basics and copy the file away, truncating the old one.

For example, if you want to ‘rotate’ the log file of data node with NodeID 3:

shell> mv ndb_3_out.log.1.gz ndb_3_out.log.2.gz
shell> cp ndb_3_out.log ndb_3_out.log.1
shell> cat /dev/null > ndb_3_out.log
shell> gzip ndb_3_out.log.1

It’s not elegant, and you might lose some entries, but it will help you keeping disk usage minimal. If you don’t need the log at all, just line 3 would do the trick.

You can use logrotate‘s copytruncate to …