A question to the internal #DBA channel at work: »Is it possible to change a column type from BIGINT to VARCHAR ? Will the numbers be converted into a string version of the number or will be it a byte-wise transition that will screw the values?«

Further asking yielded more information: »The use-case is to have strings, to have UUIDs.«

So we have two questions to answer:

• Is ALTER TABLE t CHANGE COLUMN c lossy?
• INTEGER AUTO_INCREMENT vs. UUID

Is ALTER TABLE t CHANGE COLUMN c lossy?

ALTER TABLE is not lossy. We can test.

mysql> create table kris ( id integer not null primary key auto_increment);
Query OK, 0 rows affected (0.16 sec)

mysql> insert into kris values (NULL);
Query OK, 1 row affected (0.01 sec)

mysql> insert into kris select NULL from kris;
Query OK, 1 …

MySQL uses connection and config parameters from a number of possible sources. The easiest way to find out where it is looking for config files is to run

$ mysql --help | grep cnf
                      order of preference, my.cnf, $MYSQL_TCP_PORT,
/etc/my.cnf /etc/mysql/my.cnf /Users/kkoehntopp/homebrew/etc/my.cnf ~/.my.cnf

As can be seen, my version of the MySQL client checks in this order

• /etc/my.cnf
• /etc/mysql/my.cnf
• /Users/kkoehntopp/homebrew/etc/my/cnf
• ~/.my.cnf

The cnf file is a file in dot-ini syntax, so you have [groups] and each group contains lines with key = value pairs. Which groups are read?

$ mysql --help | grep "groups are"
The following groups are read: mysql client

So in my case, I would create a /Users/kkoehntopp/.my.cnf looking like this:

[client] …

Iterating schemas over time is not an uncommon thing. Often requirements emerge only after you have data, and then directed action is possible. Consequently, working on existing data, and structuring and cleaning it up is a common task.

In todays example we work with a log table that logged state transitions of things in freeform VARCHAR fields. After some time the log table grew quite sizeable, and the log strings are repeated rather often, contributing to the overall size of the table considerably.

We are starting with this table:

CREATE TABLE `log` (
  `id` int NOT NULL AUTO_INCREMENT,
  `device_id` int NOT NULL,
  `change_time` datetime NOT NULL,
  `old_state` varchar(64) NOT NULL,
  `new_state` varchar(64) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB

That is, our log table has an id field to allow individual row addressing, and then logs the state change of a …

I recently watched a fantastic Python Pandas library tutorial series on YouTube. Without a doubt, Pandas is great for all sorts of data stuff. On the same token, MySQL Shell in Python mode is quite powerful in the sense that Python and the MySQL Shell (version >= 8.0) are somewhat united in the same environment. Although Pandas is in a league all its own when it comes to data analysis, between the power of MySQL and Python, we can also perform some basic analysis easily in MySQL Shell Python mode. In this blog post, I will cover some basic data analysis using Python mode in the MySQL Shell. Continue reading to see examples…

Business vector created by freepik – www.freepik.com

OS, Software, and DB used:

• OpenSuse Leap …

Author Andriy Lysyuk.

The unDROP for InnoDB tool can be used to recover corrupt MySQL databases. In this post, we will show how to repair a MySQL database if its files got corrupted and even innodb_force_recovery=6 doesn’t help.

The corruption of InnoDB tablespace may be caused by many reasons. A dying hard drive can write garbage, thus, page checksum will be wrong. InnoDB then reports to the error log:

InnoDB: Database page corruption on disk or a failed
InnoDB: file read of page 4.

MySQL is well known for its poor start-up script. A simple upgrade procedure may end up with two mysqld processes writing to the same tablespace. That leads to corruption too. Sometimes, power reset corrupts not only the InnoDB files, but the whole file system becomes unusable for …

 Launching Your First MySQL DB System

Step 1 - Pre-requisites

1.    1.     Create a compartment and user group to organize the resources and access. In this example, we create a compartment named as MySQL_Sandbox, and a group MySQL_Test_Group. Log-in the Console as an Administrator, under the Identity menu, create a MySQL_Sandbox compartment, and a …

 Using MySQL Enterprise Workbench to write SQL statements against MDS

Assume that you wanted to access/write sql statements on MDS from MySQL Workbench Running on On-premises (Windows OS)

How? Below are steps you needed to follow.

To connect with MySQL Workbench ,you require below details handy :-

Prerequisite:-

Guide to Migrate Production MySQL Database running on On-premises to Oracle Cloud MySQL Database Service(MDS) ?

I have one production database which i would like to migrate into Oracle Cloud PaaS model i.e MySQL Database Service , we will walk through on how to migrate customerDB database from On-premises to Oracle Cloud MySQL Database Service(MDS).

Note:- Recommended is to have MySQL DB On-Premises and MDS  both must have same version i.e 8.0 and Utility shell MySQL shell must be 8.0.21 onwards.

make sure app is disconnected and not allowing any traffic during the migration process.

We will use two new features introduced with latest release of MySQL 8.0.21.

1.       Dump Schema Utility

a.       This will help us to take the backup from On-promises database and export  to Oracle Cloud Object …

Why Does InnoDB Need A Dictionary

An InnoDB dictionary is a set of internal tables InnoDB uses to maintain various information about user tables. It serves as API between a human and the database. While the humans refer to tables by their names, InnoDB works with integer identifiers. The dictionary stores correspondence between table name and index_id.

The dictionary tables are normal InnoDB tables, but they’re not visible to a user. However, some versions of MySQL provide read-only access to the dictionary in information_schema database.

The dictionary is stored in ibdata1. Root page of SYS_TABLES, for example, has id 8, so it’s the eighth page from the beginning of ibdata1.

The dictionary pages are in REDUNDANT format even if you use MySQL 5.6. I hope to write more about record formats in future posts. For now, it’s enough to mention that REDUNDANT is the oldest record format. It was available since 4.0 …

MySQL for RDS and DBaaS, in general, are very controlled environments by the vendors, meaning that there are missing things like a SUPER grant for the root user (and any user in general). This has some implications on operations, one of them being the impossibility of running pt-table-checksum to verify data consistency between a primary and its replicas.

However, there’s a workaround that might overcome this situation and involves three things:

• The pt-table-checksum itself
• A way to collect executed queries
• And the last one, which can be controversial, is to remove the read-only from the replica and use a maintenance window to stop traffic to the database while pt-table-checksum runs.

The problem with RDS is that you cannot change binlog_format to STATEMENT, which is one of the requirements for pt-table-checksum to run.

The workaround consists of capturing the executed …