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Displaying posts with tag: Tips and Tricks (reset)
5 Database Insights Easy to See with VividCortex SaaS Monitoring

There are manifold ways to collect, visualize, and analyze data… but not all methods are equally useful. VividCortex, however, is singular as a database-centric SaaS monitoring platform, and it's designed to provide you with powerful insights into your system that are both inherently actionable and unique. Within minutes of first booting up VividCortex, users frequently discover new aspects of their system. They understand it in brand new ways, just by viewing our app’s basic dashboards and metrics.

But that's just the start. Even beyond those initial revelations, there are many more powerful insights that VividCortex can provide, if you know how and where to look. These views aren’t entirely automatic, but they’re simple to discover with a few tips. Here are 5 insights easy to see with VividCortex.

Find which queries affect the most rows

Understanding which queries are …

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How to setup MySQL replication on CentOS

In this tutorial we will show you how to setup basic MySQL replication on two CentOS 7 servers, but the same steps should work on all RPM based systems. We will use two test CentOS 7 virtual servers for this tutorial with the following IP addresses: MASTER: 123.456.789.1 SLAVE: 123.456.789.2 Master Server: Login to the master server as user root ssh root@IP_Address and install MySQL server if it is not already installed yum install mysql-server mysql Start the MySQL server and enable it to start at boot time systemctl start mysql systemctl enable mysql Next, open the MySQL configuration file […]

Fun with MySQL Cluster Memcached #1 - "ERROR: You can't mix -e with the old options"

When using the bundled memcached that comes with MySQL Cluster and trying to set one of the 'classic' options along with passing the cluster connect string with -e you may end up getting the following message:

  ERROR: You can't mix -e with the old options

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Configuring email in the Cloud

What a relief! A few simple configuration steps gives me new hope for coping with email.

It unlikely matters to you, but it does to me: My inbox is down to zero. That is, both my two inboxes are empty. I get work email to my @skysql.com address and private email to my @arno.fi, both of which have been suffering from bad email habits.

Inspired by years of discussions with Giuseppe Maxia, who is living proof that proper IT tools make geeks work smarter, faster and better, I bought the book "lifehacker". The first one out of over 100 hacks is labeled "Empty Your Inbox (and Keep It Empty"), so I judged that piece of advice to be worth following.

That was a few hours ago. No, in that short …

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Nasty InnoDB regression in MySQL 5.5.25

We just ran into a nasty InnoDB bug that only seems to exist in MySQL 5.5.25:

An InnoDB update that modifies a rows primary key can trigger some recursive behavior that creates new rows until all disk space is exceeded. This does not affect all primary key updates in general but only gets triggered when a few other conditions are also met, so you're not too likely to run into it, but if you do your mysqld server will waste a lot of IO bandwidth and storage space on this and will usually eventually run out of disk space.

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Adding a case insensitive, distinct unicode collation

Every once in a while questions like the one in MySQL Bug #60843 or Bug #19567 come up:

What collation should i use if i want case insensitive behavior but also want all accented letter to be treated as distinct to their base letters?

or shorter, as the reporter of bug #60843 put it:

I need something like utf8_bin + ci

utf8_general_ci and utf8_unicode_ci unfortunately do not provide this behavior and utf8_bin is obviously not case insensitive.

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Using the MySQL stack trace to isolate bugs

I came across an interesting error reported on #mysql the other day. When I went through it with the reporter it looks like we uncovered up to two bugs in InnoDB (or rather XtraDB as it was Percona Server). I thought it might be useful to go through the error message, including the stack trace, to show that you don't need to be a developer to track down some useful information.

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SkySQL Presents a New Community Resource

SkySQL has always been committed to the MySQL® community and today we've unveiled a new resource page for the community. This is designed for the community to get a single point of information, assistance, and inspiration. While we are starting quite modestly it is up to you, the community, to make this the best resource for MySQL and related technologies.

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Consistent transactions between storage engines

You may not realize it, but in MariaDB 5.2 and earlier and in MySQL up to version 5.5, START TRANSACTION WITH CONSISTENT SNAPSHOT does not give any guarantees of consistency between different storage engines.

For example, suppose you have two transactions which run in parallel:

Transaction T1:

BEGIN;
    SET @t = NOW();
    UPDATE xtradb_table SET a= @t WHERE id = 5;
    UPDATE pbxt_table SET b= @t WHERE id = 5;
    COMMIT;

Transaction T2:

SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;
    START TRANSACTION WITH CONSISTENT SNAPSHOT;
    SELECT t1.a, t2.b
      FROM xtradb_table t1 INNER JOIN pbxt_table t2 ON t1.id=t2.id
    WHERE t1.id = 5;

In the above case, it is possible, even with a "consistent" snapshot, to see the changes in a transaction only in InnoDB/XtraDB tables, and not in PBXT tables.

Naturally, it would be much better if the changes were visible no matter the …

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How to produce a full stack trace for mysqld

The information here was adapted from the AskMonty Knowledgebase.

There are two main parts to MariaDB and MySQL: The mysqld server and whatever client you use to interact with the server. The server is absolutely essential and must remain up and running. mysqld is normally very reliable, but there are rare occasions when it will fail. When mysqld fails hard (or core dump) it will, by default, write a stack trace in the 'hostname'.err file in the database directory. However, in some cases this is not enough to find out exactly what happened.

If you ever run into a situation where mysqld crashes and the 'hostname'.err file does not contain enough information for your DBA or support provider to diagnose the problem, you may need to use what is known as a "debug" build to produce a "full stack trace" and a core file. …

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