A friends table is the cornerstone of social applications. Its purpose is to define relationships and help answer the question what are my friends doing.

Here is an example friend’s table:

 CREATE TABLE `friends` (
  `user_id` bigint(20) unsigned NOT NULL,
  `friend_id` bigint(20) unsigned NOT NULL,
  `auto_ts` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`user_id`,`friend_id`),
  KEY `user_id-auto_ts` (`user_id`,`auto_ts`),
  KEY `friend_id-auto_ts` (`friend_id`,`auto_ts`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci


With the table above we can get a list of user_ids a user follows (following), or a list of people who follow said user (followers), or get a list of mutual follows. This is a very simple table structure yet very powerful.
…

We are excited to announce that VividCortex now supports Redis, a popular open source database. After announcing PostgreSQL support in January, our brainiacs continue to create a unified solution for diverse systems.

Baron Schwartz explains the product development further. “Redis is an important database for VividCortex, both strategically and commercially, due to its incredible popularity and our own usage. We rely on Redis to help analyze the massive amounts of time-series data we receive from agents running on customer systems. Although it is a high-performance and reliable system that generally just works, that doesn’t mean it can’t be improved. We were able to significantly optimize our usage of Redis with the network-traffic visibility built into our agents. Most of our …

Most of the time I like pt-kill, but sometimes it gets a little overzealous and kills a query that I need. That's why I'm glad Percona created pt-reanimate so I can bring those important queries back to life. Of course the queries are not exactly the same when they come back, but at least they come back.

Here's an example of pt-reanimate in action. First I add a column to a large table:

alter table big_table add column new_col int;

Here is my DDL in the processlist table:

+---------+------+----------------+----------------------------------------------+ | command | time | state | info | +---------+------+----------------+----------------------------------------------+ | Query | 146 | altering table | alter table big_table add column new_col int | …

I have done a lot of benchmarks of MySQL Cluster on large servers which
is obviously very interesting. As mentioned in a previous blog I have
an Intel NUC machine now easily accessible. So I thought it would be
fun to make some benchmarks on this machine to see how fast MySQL Cluster
runs on small HW.

First a little description of the HW. The CPU is an Intel Core i5-4250
CPU. It runs at 1.3GHz and have a turbo frequency of 2.3 GHz. The CPU
has two cores and each core can run two threads simultaneously
(called hyperhtreading in Intel CPUs). It comes with the box containing
the motherboard and the CPU. Then you buy one or two DRAMs to it and an
SSD drive. I installed two DDR3L DRAMs which gives me a total of 16GByte
memory in the machine. In addition I installed an SSD drive of 256GByte.
The box fits nicely into the palm of your hand.

On …

A Quick Security Update

Starting with MySQL 5.7.6, the following functions are now deprecated:

• DES_ENCRYPT
• DES_DECRYPT
• ENCRYPT

DES (Data Encryption Standard) is known to be less secure and slower than other available encryption methods. There are also many …

Yes, after many hours, late nights, hair pulling, some private yelling:

core@master ~/mysql_replication_kubernetes/galera_sync_replication $ kubectl get pods
POD                 IP                  CONTAINER(S)        IMAGE(S)                                     HOST                            LABELS              STATUS
pxc-node1           10.244.72.7         pxc-node1           capttofu/percona_xtradb_cluster_5_6:latest   172.16.230.136/172.16.230.136   <none>              Running
pxc-node2           10.244.15.2         pxc-node2           capttofu/percona_xtradb_cluster_5_6:latest   172.16.230.134/172.16.230.134   <none>              Running
pxc-node3           10.244.42.2         pxc-node3           capttofu/percona_xtradb_cluster_5_6:latest   172.16.230.135/172.16.230.135   <none>              Running

mysql> show status like 'wsrep_incoming_addresses';
+--------------------------+----------------------------------------------------+
| …

Wed, 2015-04-01 10:28guillaumelefranc

Upgrading a running MariaDB Galera Cluster from 5.5 (previous stable) to 10.0 (stable) is a question which comes up frequently with Remote DBA customers. Although a standard migration from 5.5 to 10.0 is well covered in the Knowledge Base, Galera Cluster upgrades haven’t been really documented in detail now. This howto will cover upgrades on CentOS or RHEL 6 but a similar logic can be applied to Ubuntu/Debian as well.

Prerequisites

It is indeed possible to do a rolling cluster upgrade if the Galera API and provider versions are compatible. Please refer yourself to my previous blog article (https://mariadb.com/blog/deciphering-galera-version-numbers) if you need to understand more about Galera versioning. A simple way to ensure Galera compatibility is to upgrade first to the latest 5.5 Galera …

Recently Todd Farmer shared an interesting story about the mysql command line prompt in MySQL 5.7: how it was changed to provide more context and why the change was finally reverted. This made me think that after using the command line client for MongoDB for awhile, I would love seeing a much more modern mysql shell prompt. Here are a few examples of what a modern command line client can do.

Add dynamic information to the prompt

If you use replication with MongoDB, you have probably noticed a nice feature of the prompt: it is replication aware. What I mean is that for a standalone instance, the prompt is simply:

>

When you configure this instance to be the primary of a replica set named RS, the prompt automatically becomes:

RS:PRIMARY>

and for secondaries, you will see:

1) Update_time not accurate in information_schema.tables

Information_schema.tables has a field called update_time and in 5.6 you will notice that it is always NULL. Future versions of MySQL will fix this problem

2) Multiple instance manager

Currently creating , managing and dropping instances in MySQL requires many DBA hours. mysqld_multi is there to help you but it requires initial configuration and there are other third party utilities that could come to your rescue

It would be better to have built in utilities to help us in this regard.. For example db2 has db2icrt that creates an instance , db2ilist to list instances and db2idrop to drop an instance

3) Quiesce database in MySQL

There is no built in quiesce option to block all activity on the database/instance. Although method mentioned in  below URL will help you in doing manual quiesce …

Everything seemed complete after configuring my standalone MySQL instance to a LAMP installation, but last night I started playing with the image files. It turns out that I failed to install the php-gd library.

There’s very little feedback when you try to troubleshoot why you can’t read an image. In fact, the error message for reading the BLOB from MySQL was only available on the local Firefox browser:

      The image "http://localhost/ConvertMySQLBlobToImage.php" cannot be displayed because it contains errors.

The fix requires root to install the php-gd library with the yum utility:

yum install php-gd

You’ll need to answer …