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Showing entries 1 to 17

Displaying posts with tag: Intermediate (reset)

Recovering a MySQL `root` password – Three solutions
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Three ways to recover a root user password:

The order of solutions here under gets more creative on the way down :)

1. obviously, before starting messing around check my.cnf or scripts for passwords entries, then try home directories for password files
2. secondly – can you restart mysql? if yes, restart with –skip-grant-tables, log into mysql, change your password and restart without –skip-grant-tables
3. third option – (on linux / unix ONLY)
If you haven’t found the password anywhere and can’t afford to restart your mysql.

cd data/mysql
cp -rp user.MYD bck_user.MYD_`date +%Y%m%d`
cp -rp user.MYD /tmp/user.MYD
vi /tmp/user.MYD #(edit the hashed passwords next to root*)
cp -rp /tmp/user.MYD user.MYD
sudo kill -HUP `pidof mysqld`

Note that the latter method of recovering a




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Could not find first log file name in binary log index file
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Scenario Master – Master replication

MasterA is a client facing server
MasterB is a warm standby server (read only)

MasterB restarted abruptly and when instances were braught back up MasterA (it’s slave) was showing the following error:

MasterA has the following error in show slave status:
Last_IO_Errno: 1236
Last_IO_Error: Got fatal error 1236 from master when reading data from binary log: ‘Could not find first log file name in binary log index file’

Solution:

Slave: stop slave;

Master: flush logs
Master: show master status; — take note of the master log file and master log position

Slave: CHANGE MASTER TO MASTER_LOG_FILE=’log-bin.00000X′, MASTER_LOG_POS=106;
Slave: start slave;

CRIB – CentRal Information Base for MySQL
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CRIB is a CentRal Information Base for MySQL, a long time coming project since I worked on it on and off for a few weeks and now I decided it’s time to hand it over to the global MySQL community.

So, what is CRIB?

CRIB is a central database which collects information about all your MySQL instances which you set as clients. It is monitoring in a way, but not the typical number of connections, memory, index usage, table scans, cpu usage and such, but rather consists of a repository where, if you have tens, hundreds or even thousands of clients, you can see where a particular user was created, where a certain database name features or which tables does a database consists of. It also features a script which logs table sizes periodically (customizable) so you can graph disk usage over time and be able to forecast future disk space requirements

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Do you use MySQL replication? Do you use “FLUSH LOGS”? If yes you might want to read this.
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Scenario: Master-Master replication
Description: Master A is the active db server whilst Master B is a read only swappable db server hence both are creating binary logs. During backup I run “FLUSH LOGS” in order to have a simpler point in time recovery procedure if that case arises.
Problem: Flush logs is mean mean command :) …. it rotates not only my binary logs but my error log too (since I user error-log=blahblahblah in my my.cnf). Well given I flush logs every night my error log is cycled through every night, but unlike binary logs which have an incrimental number attached to the fine, error logs only have a `-log` attached to the filename and a second “FLUSH LOG” would just clear all error logs permanently. That is really not fun believe me!

So what is the solution?



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Getting a return code from a stored procedure
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Sometimes we have some special need for a stored procedure to call another to do something. That is fine, but what if the second stored proc failed for some reason? Maybe you want to halt the first stored procedure (the caller) and not proceed with the work until the problem is verified and resolved. So How do you do it?

Simple, get a return code from the called procedure to determine if it worked or not!

Here’s a sample piece of code to explain better:


DROP PROCEDURE IF EXISTS `test`.`testing123`;
DELIMITER $$

CREATE
PROCEDURE `test`.`testing123`(OUT a INT)
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
SET a=2;
END;
SET a=0;

# toggle the below as comment or not to see the call at the bottom working
#










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Datetime & Timestamp manipulation / migration explained
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Are you doing some datetime manipulation or maybe you are migrating from some database technology to MySQL or possibly using milliseconds?
Here is an example on how to go about it:

Say you have the following date: MAR 16 2008 09:12:51:893AM
SELECT DATE_FORMAT(STR_TO_DATE('MAR 16 2008 09:12:51:893AM','%M %d %Y %h:%i:%s:%f%p'),'%Y%m%d%k%i%s.%f'); --> 2008031691251.893000

What if its PM rather than AM
SELECT DATE_FORMAT(STR_TO_DATE('MAR 16 2008 09:12:51:893PM','%M %d %Y %h:%i:%s:%f%p'),'%Y%m%d%k%i%s.%f'); --> 20080316211251.893000

Ok so this is just simple string manipulation where:
%M is the month name
%d is day number
%Y is the year
%h is the hour
%i is the minute
%s is the second
%f is the microsecond
%p is the












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Automating MySQL access with expect and bash scripting
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If you have multiple database servers with strange names, or if you have to hop over multiple machines to connect to any mysql database server, then you know what a pain it can be to administer such a setup. Thanks to some scripting, you can automate such tasks as follows:

Create an expect script:
/path/to/sshmysql.exp

#!/usr/bin/expect -f
#script by darren cassar
#mysqlpreacher.com

set machine [lindex $argv 0]

set timeout -1

spawn ssh username@$machine
match_max 100000
expect -exact “assword: “
send — “password\r”
send — “sudo -k; sudo su – mysql\r”
expect -exact “sudo -k; sudo su – mysql”
expect -exact “assword:”
send — “password\r”











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MySQL vs InfoBright optimizer battle
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MySQL instance running an Infobright engine


mysql> explain SELECT COUNT(ac.UID) FROM ACTIVE ac JOIN ALL a;
+----+-------------+-------+------+---------------+------+---------+------+---------+-------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+------+---------------+------+---------+------+---------+-------+
| 1 | SIMPLE | ac | ALL | NULL | NULL | NULL | NULL | 124426 | |
| 1 | SIMPLE | a | ALL | NULL | NULL | NULL | NULL | 7594256 | |
+----+-------------+-------+------+---------------+------+---------+------+---------+-------+
2 rows in set (0.01 sec)

mysql> SELECT COUNT(ac.UID) FROM ACTIVE ac JOIN ALL a ON ac.UID=a.UID;
+---------------+









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Once upon a timestamp(milliseconds)….
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Once upon a time`stamp`, in a `data`base far far away, someone filed a bug named: `Microseconds precision is not retained by TIME, DATETIME, and TIMESTAMP field types.` – Bug Number 8523. This was the beginning of 2005, yet now that we are approaching the end of 2009, after 4.5 years, many (including myself) are still asking for this.

In fairness sake, MySQL have indeed supplied a way to retain milli and micro seconds in a decimal field `DECIMAL(17,3)`, and it is also queryable as if it were a timestamp BUT why isn’t it possible to store in a `DATETIME` or `TIMESTAMP` field? Why can’t we run a ’select now()’ or ’select curtime()’ etc and get a full timestamp including milli / micro seconds?

I have counted 37 different usernames asking for this feature, spanning from 15th Feb 2005 to recently. (list found below)

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Security – Roles and Password Expiry on MySQL using SECURICH
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Lately there has been quite some talk about security on MySQL, and I've decided to GPL a package I wrote, implmenting Roles on MySQL. This technology has been available on other databases for quite some time, but hasn't quite yet made it to MySQL's feature list and apart from this tool, the only solution I know of is google's patches for MySQL 5.0.
Replicating from MySQL to *
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Recently I needed to replicate between MySQL and another database technology. You might say, why on earth would you want to do something like that, but believe me there are reasons and definitely not (to go away from MySQL to some other DB technology like Oracle or SQL server). Unsurprisingly there are quite a few different tools to do it from any platform towards MySQL but very few which do it the other way round, just to name a couple: Golden Gate and DSCallards.
MCDBA Certification – KPIs
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A few interesting KPIs about certified people and their current location (the fact that many people travel from one country to the other for work is very popular these days especially in the IT sector): Before starting to read, I am hereby assuming the MySQL list of MCDBAs is on a residence basis not citizenship. There are [...]
MySQL HA – Let’s take a look at Sequoia
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MySQL HA: 1. Desirable – most of the time, 2. Needed – often enough, 3. Available – there are some good options out there. Typical solutions consist of: Heartbeat with DRBD on Linux. Although HB was introduced to Linux, it can be used on Solaris, FreeBSD and others without the DRBD but with other solutions. Sun Cluster, Veritas (commercial), MySQL Proxy (still in [...]
Save time and energy: How to …
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Save time and energy: How to:

Listening to “Highway to Hell” in an Oxford University computer lab on a sunday afternoon writing a MySQL blog can be legitimally defined by some as sick but thats what a geek calls a relaxing yet productive sunday afternoon.

For the sake of all those CLI ambassadors like myself, I wanted to share a couple of tips and tricks I use quite often when doing my mysql db administration work / scripting. I strongly suggest any mysql dba / dev use CLI simply because thats the one thing you should always have on any machine on which mysql is installed, be it Unix, Linux, Mac, Microsoft or whatever platform you are using.

Cancelling a query you are typing without exiting to the terminal:
`\c` – How many times you ended up hitting `CTRL+C` (default process kill in most OSes) in order to cancel a command, finding

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Slap’em
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Giving a bunch of mysql instances something you do everyday and you might think ….. how should I do it? Write a bunch of selects and inserts manually? nahh that takes s**tload of time, should I run binlogs collected from a live system on my test server? nahh thats not practical nor is it real since it doesn’t contain selects, should I gather the general query log and try that out? nahhh  …..

MySQL has been kind enough to supply us with their mysql_slap which does the job for us and given I needed to do a proof of concept on monitoring a group of 4 circular replicated servers I wrote a small script which does the job of slapping them with a varying level of concurrancy, iterations, number of queries and connections for as long as you like.

Here it is and I hope some of you might find it useful for slapping their own test servers :).

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Circular Replication Implementation / Testing using MySQL Sandbox
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This is a simple mysql circular replication implementation on a single machine (just a proof of concept) which can easily be done on a broader scale. Just be aware of the cons of circular replication which mainly gets down to: once a node freaks out or stops for one reason or the other, it’s a bitch and you need to take care of IMMEDIATELY.

Download Sandbox from https://launchpad.net/mysql-sandbox/+download
Download MySQL from http://dev.mysql.com/downloads

Copy the downloaded software onto the your *nix box onto any folder of your preference called $BASEDIR

run:

cd /$BASEDIR

gunzip mysql_sandbox_X.X.XX.tar.gz
tar -xf mysql_sandbox_X.X.XX.tar

ln -s mysql_sandbox_X.X.XX sandbox

time /$BASEDIR/sandbox/make_replication_sandbox –circular=4 –topology=circular



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MySQL Installing: Binary tarball (.tar.gz) *nix based platforms
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Installing MySQL is quite an easy thing to do, especially when done using pkgs, dmgs or exes. It gets just a tad more time consuming and brain intensive when installing a .tar.gz binary package. It is when you’re compiling MySQL source directly that you’ll need some planning and playing, but the latter is only done in particular cases such as when you’ll need a particular engine not shipped with a pre-compiled package etc.

Today we’re going through the steps required for a typical MySQL installation from a .tar.gz package on a *nix based platform, including the download, installation, configuration and securing.

Steps involved:
1. Download MySQL binary tarball from mysql.com
2. Create a folder structure where the installation will be held.
3. Install the package
4. Secure the



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Showing entries 1 to 17

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