IS NULL, IS NOT NULL, truthiness among other assertions on MySQL and PostgreSQL

People like to complain about JavaScript, how can one thing be equal to the other, i.e. null == undefined evaluates to true unless you use the triple equals ===. Other dynamic typed languages have its peculiarities, such as Ruby where 0 == true evaluates to true, the reason for Ruby is that considers 0 as a value and any value evaluates to true.

How about SQL? The answer is… it depends.

Which database are you using?

Some may be more forgiving, like MySQL doing casts for you all over the place, or more strict like PostgreSQL where you can only compare the truthiness of something of the same type.

• Replication used to replicate data from the Master node to a slave node[Replica].
• By default Replication is asynchronous.
• It uses binary logs for reading data from the Master node and relay log on slave[Replica].
• Depending on the configuration, you can replicate all databases, selected databases, or even selected tables within a database.

Replication Methods:

• File-based Replication:

The traditional method is based on replicating events from the master’s binary log, and requires the log files and positions in them to be synchronized between master and slave.

• GTID Replication:

The newer method based on global transaction identifiers (GTIDs) is transactional and therefore does not require working with log files or positions within …

In Generic binary Installation method, we are extracting compressed tar files of MySQL and later we can do customization for MySQL setup as per our requirement. Like having different data directory, log directory etc.

MySQL Generic Binaries can be used to install MySQL on Unix/Linux platforms.

MySQL Installation has a dependency on the libaio library. Make sure that is there on a server before mysql install.

• Create a mysql user and group, which we will use as a service account for the mysql server.

shell> groupadd mysql

shell> useradd -r -g mysql -s /bin/false mysql

• Extract MySQL binaries TAR to mysql base directory for example in /mysql dir

• Create require directories and set appropriate permissions.

shell> cd mysql

…

Point In Time Recovery - is a nightmare for DBAs if the MySQL clusters are self managed. It was 10PM, after had my dinner I was simply watching some shows in YouTube. And my phone was ringing, the customer on other side. Due to some bad queries, one of the main table get updated without where clause. Then suddenly everyone joined the call and asking me to bring the data back. That day it took 6 to 8 Hours to bring the data. Yes, every DBAs will do one or two biggest mistakes. In my carrier I would say this was that day. So here is my MySQL PITR the fastest way with DevOps.

Where I failed in this DR setup?

• PITR starts with last full backup + binlogs
• I missed in my backup script to add --master-data, So I don’t know how to start applying binlogs.
• No Delay replica. I got the call within 10mins when the data has been messed up. But all of my replicas are real time sync. Its affected all of …

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I few months ago, I wrote about using the Django framework with MySQL 8. There are also other Python frameworks that are worth considering. In this blog, I will look at using SQLAlchemy with MySQL 8.

In order for you to be able to use MySQL 8 with SQLAlchemy, you need three pieces of software: MySQL Server, MySQL Connector/Python, and SQLAlchemy. I will go through the installations, then I will look at a code example.

Information

The examples in this blog uses MySQL Server 8.0.15, MySQL Connector/Python 8.0.15, and SQLAlchemy 1.2.18. It should be possible to reuse the instructions with other MySQL versions as well, except in older MySQL versions you …

The latest enhancement in ProxySQL v2.0.0 is the native support of Galera Cluster. No more need to use an external script within the scheduler like explained also in this post of ours.

This document will cover how to take an advantage of the new feature and integrate ProxySQL with Percona XtraDB Cluster to monitor galera node status and read-write split performed by ProxySQL. To illustrate we will use a cluster of 3 nodes, below are the details:

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MySQL changed the timestamp format in the log files in MySQL 5.7. Since then, I have a few times seen questions about the new format, and how to change the time zone that is used. Latest in a comment to my blog about log_slow_extra in 8.0.14, where the question was what T and Z in the timestamp (for example 2019-01-31T07:24:06.100447Z) means. In this blog, I will discuss the timestamp format and show you how you can change the time zone used.

Examples of the timestamps from the MySQL error log when restarting MySQL (click to enlarge).
The MySQL 5.7 Change

In MySQL 5.7 it was decided to make two …

Since January 2019 FromDual tries to contribute actively a little bit against global warming too.

The best for the climate would be to NOT travel to the customer at all! For this cases we have our FromDual remote-DBA services for MariaDB and MySQL.

But sometimes customer wants or needs us on-site for our FromDual in-house trainings or our FromDual on-site consulting engagements. In these cases we try to travel by train. Travelling by train is after walking or travelling by bicycle the most climate friendly way to travel:

• Die SBB steigt um auf Bahnstrom aus 100 Prozent …

Data is captured and stored for a variety of reasons. Hours beyond count (and even more budget) invested in collecting, ingesting, structuring, validating, and ultimately storing of data; to say that it is a valuable asset is to drive home a moot point. This day in age it may, in fact, be our most precious commodity.

Some data is used strictly as an archive. Perhaps to record or track events that happened in the past. But the other side of that coin is that historical data has value in basing decisions for the future and future endeavors.

• What day to have our sale on? (Planning for future sales based on how we did in the past.)
• Which salesperson performed the best in quarter one? (Looking back, who can we reward for their efforts.)
• Which restaurant is frequented the most in the middle of July? (The travel season is upon us... Who can we sell our foodstuffs and goods to?)

You get the …

Percona is glad to announce the release of Percona XtraDB Cluster 5.6.43-28.32 on February 28, 2019. Binaries are available from the downloads section or from our software repositories.

This release of Percona XtraDB Cluster includes the support of Ubuntu 18.10 (Cosmic Cuttlefish). Percona XtraDB Cluster 5.6.43-28.32 is now the current release, based on the following:

• Percona Server 5.6.43-84.3
• Codership WSREP API release 5.6.42
• Codership Galera library 3.25

All Percona software is …