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10 Newer Entries Showing entries 121 to 130 of 889 10 Older Entries

Displaying posts with tag: Uncategorized (reset)

Raspberry Pi – Running MySQL Cluster
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So my colleague Andrew Morgan did this a year or so ago, but I wanted to repeat his experiment and add a few features in order to make it a live demo. It should show how MySQL Cluster (CGE) can run even on very modest hardware..

 

The hardware has been purchased

2x Raspberry Pi’s (model b)

1x Adafruit LCD Pi Plate (16×2 LCD)

USB Hub for power

HDMI -> DVI adaptor

Netgear 100/Mbs Switch

 
Watch this space

 


So what is this all about?
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So the purpose of this blog is just to share with the world for those who are interested on what i’m working on in my role of Sales Consultant for Oracle MySQL in the Uk.


MySQL force user change password
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Since version 5.6.6 MySQL has introduced the capability to force an user to change their password.
You can archive that by issue ALTER USER PASSWORD EXPIRE statement.

ALTER USER 'marcelo'@'localhost' PASSWORD EXPIRE;

Next time marcelo tries to login from localhost it will block all statements rather then SET PASSWORD;

mysql> \s
ERROR 1820 (HY000): You must SET PASSWORD before executing this statement

To remove this block, just issue an :

SET PASSWORD = PASSWORD('pwd');
#Or use the hash received from SELECT PASSWORD('pwd');
SET PASSWORD = '*975B2CD4FF9AE554FE8AD33168FBFC326D2021DD';

But be careful, if you expire the password for


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MEM in WB
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In the new Workbench, click on the "Planet MySQL" shortcut, then search for my feed and find this post.

MEM

Big Data from Space: the “Herschel” telescope.
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” One of the biggest challenges with any project of such a long duration is coping with change. There are many aspects to coping with change, including changes in requirements, changes in technology, vendor stability, changes in staffing and so on”–Jon Brumfitt. On May 14, 2009, the European Space Agency launched an Arianne 5 rocket [...]
“Duplicate Entry” error for key PRIMARY on UPDATE query (RBR + Triggers)
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Recently, I have faced one interesting issue with Master(Active)-Master(Passive) replication (RBR + Triggers). Passive master was stopped due to “Duplicate Entry” error with update statement. It was something like this. Last_Error: Error ‘Duplicate entry ’29014131′ for key ‘PRIMARY” on query. Continue reading →   [Read more...]
EXPLAIN FORMAT=JSON vs regular EXPLAIN
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Valeriy has mentioned that MySQL manual has no documentation about EXPLAIN FORMAT=JSON feature. There was a bug filed for this since September, 2012. I had spent some time looking at EXPLAIN FORMAT=JSON, so I thought I would share my findings.

The first blog post about EXPLAIN FORMAT=JSON was made by Sheeri. She listed these features of FORMAT=JSON:

  • attached_condition and implicit casts
  • used_key_parts field

In addition to those, I was able to find

  • Pushed index condition information
  • More information about sorting/grouping
  • Subquery attachment points
  [Read more...]
Creating and restoring database backups with mysqldump and MySQL Enterprise Backup – Part 1 of 2
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Be sure to check out my other posts on mysqldump:
Scripting Backups of MySQL with Perl via mysqldump
Splitting a MySQL Dump File Into Smaller Files Via Perl

Part 1 of 2: (part two)
If you have used MySQL for a while, you have probably used mysqldump to



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MySQL 5.6, InnoDB statistics, and testcases for optimizer
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One of the new features in MySQL 5.6 is persistent table statistics. The word “persistent” makes you think that table statistics will be very stable from now on.
This is generally true, but there are some exceptions. There is a particular case where InnoDB statistics may change with no warning, even when there is no user activity on the server. Consider the following pattern (which nearly all bug or feature testcases follow):

CREATE TABLE t1 (...) ENGINE=INNODB;
INSERT INTO t1 VALUES (1),(2),(3),(4),(5);
EXPLAIN SELECT * FROM t1;
EXPLAIN SELECT * FROM t1;

With MySQL 5.6, the following is possible

  • the first EXPLAIN will show that the optimizer expects table t1 to have 6 rows
  • the second EXPLAIN will show that the optimizer expects table t1 to have 5 rows

For me, this was a big surprise. After all, table t1 never had 6 rows. If there was some


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What the Mean Really Means
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When analyzing response time, or latency, you need much more information than an average provides. The average, commonly the arithmetic mean, shows the index of central tendency. But, as I found in earlier posts, the tendency is often not central, but may be skewed by outliers, or split by multiple modes. How often these factors occur was determined quantitatively, using tests and a survey of hundreds of production servers and different types of latency: over 95% had six-sigma outliers, and

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10 Newer Entries Showing entries 121 to 130 of 889 10 Older Entries

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