Next up in the "quick look" series is a discussion of connection management best practices and the memory usage implications of idle connections in Aurora and MySQL. I'll also throw in some notes on how to configure your connection pools to avoid unpleasant surprises.

Thread handling in Aurora vs MySQL Community MySQL editions use "one-thread-per-connection" approach to thread handling. It means that each individual user connection receives a dedicated OS thread within the mysqld process. This comes with issues, such as: 

• Relatively high memory usage with large number of user connections, even if the connections are completely idle.
• Higher internal server contention and context switching overhead when working with thousands of user connections.

To avoid such issues, some servers support a thread pool approach. Examples include Percona Server and Amazon Aurora.

…

Join Percona’s Chief Evangelist, Colin Charles as he presents MariaDB Server 10.2: The Complete Guide on Tuesday, June 27, 2017, at 7:00 am PDT / 10:00 am EDT (UTC-7).

Register Now

The new MariaDB Server 10.2 release is out. It has some interesting new features, but beyond just a list of features we need to understand how to use them. This talk will go over everything new that MariaDB 10.2 has to offer.

In this webinar, we’ll learn about Window functions, common table expressions, finer-grained CREATE USER statements, and more – including getting mysqlbinlog up to parity with MySQL. …

Indexing and the MySQL Document StoreThe MySQL Document Store allows developers who do not know Structured Query Language (SQL) to use MySQL as a high efficient NoSQL document store. It has several great features but databases, NoSQL and SQL, have a problem searching through data efficiently. To help searching, you can add an index on certain fields to go directly to certain records. Traditional databases, like MySQL, allow you to add indexes and NoSQL databases, for example MongoDB, lets you add indexes. The MySQL Document Store also allows indexing.

So lets take a quick look at some simple data and then create an index.

mysql-js> db.foo.find()
[
    {
        "Name": "Carrie",
        "_id": "888881f14651e711940d0800276cdda9",
        "age": 21
    },
    {
        "Name": "Alex",
        "_id": "cc8a81f14651e711940d0800276cdda9",
        "age": 24
    },
    {
 …

This Log Buffer Edition covers Oracle, SQL Server and MySQL.

Oracle:

You may wish to clone an Oracle Home (for example you have all your databases on a single Oracle Home, but you want to separate Development from Test

Removing Outliers using stddev()

Installing Scala and Apache Spark on a Mac

Introduction to Oracle Big Data Cloud Service – Compute Edition (Part V) – Pig

More on …

This Log Buffer Edition covers Oracle, SQL Server and MySQL.

Oracle:

You may wish to clone an Oracle Home (for example you have all your databases on a single Oracle Home, but you want to separate Development from Test

Removing Outliers using stddev()

Installing Scala and Apache Spark on a Mac

Introduction to Oracle Big Data Cloud Service – Compute Edition (Part V) – Pig

More on …

In several RDBMS databases, including MySQL, subqueries are often one of the causes for performance issues. Therefore, we have an incentive to avoid them whenever we can and to find alternative ways to implement our requirements.

One of the most popular uses for subselects in SQL is when one needs to fetch the first, last, maximum or minimum row for each group in a table. For example, how would you implement an SQL query that should fetch the employees with the maximum salary for each department from the employees table? Actually, fetching the salary itself is pretty easy, but it becomes more complicated when you want to fetch the employee name (the row data) along with the maximum salary.

Let’s look at the table:

For the impatient:

# echo -e "deb http://repo.mysql.com/apt/debian/ stretch mysql-5.7\ndeb-src http://repo.mysql.com/apt/debian/ stretch mysql-5.7" > /etc/apt/sources.list.d/mysql.list
# wget -O /tmp/RPM-GPG-KEY-mysql https://repo.mysql.com/RPM-GPG-KEY-mysql
# apt-key add /tmp/RPM-GPG-KEY-mysql
# apt update
# apt install mysql-server

In the latest stable version of Debian, if you ask to install mysql-server, you now get installed mariadb automatically, with no (evident) way of installing Oracle’s MySQL. Any major version upgrade has to be done carefully (not only for MariaDB, but also for MySQL and Postgres), and I bet that a MySQL 5.5 to MariaDB 10.1 will cause a huge confusion. Not only it will fail user expectations, I think this will cause large issues now that MariaDB has chosen to become a “hard” fork, and become incompatible in many ways with MySQL. Not only the server upgrade will cause user struggle, the connector is …

Last Thursday, I was introducing MySQL Document Store in Ghent, BE at Percona University.

I was explaining how great is this technology and how MySQL can replace your NoSQL database but still provides you all the benefits from a RDBMS.

This is the full presentation:

Introduction to MySQL Document Store from Frederic Descamps

Then somebody came with a nice question. Let me put first some context:

• we will create a collection to add people in it
• we will create a virtual column on the age
• we will index that column
• we will query and add records to that collection

Collection creation and add some users

mysql-js> schema = …

以前の記事では、MySQL 8.0.1で導入された新しい 日本語のutf8bm4のCollation(文字照合順)について ご紹介しました。このcollation (utf8mb4_ja_0900_as_cs) は、CLDR 30で定義されたアクセント記号(清音濁音半濁音)ならびに大文字小文字(拗音促音など)を判別する実装となっています。

今日ご紹介するのはひらがなカタカナを判別できる新しい「かなセンシティブ」なCollation utf8mb4_ja_0900_as_cs_ksです。 …

MySQL 8.0.1では、utf8mb4の大文字小文字およびアクセント記号付きの文字を判別するas_cs collationに加えて、日本語用のCollation(文字照合順)を追加しました。

utf8mb4_ja_0900_as_csについて

日本語に関する文字照合およびソートのルールは複雑です。日本語ではひらがな、カタカナ、漢字、アルファベット(ラテン文字)を混在させて利用しています。さらに、全角と半角が存在する文字もあります。では、‘あ’, ‘ア’, ‘a’, ‘ｱ’はどのようにソートされるのでしょうか？

Unicode照合アルゴリズム(UCA / Unicode Collation …