MySQL HeatWave enables users to process and query hundreds of terabytes of data in the object store—in a variety of file formats, such as CSV, Parquet, and Aurora/Redshift export files. This ability to store data on Object Storage and retrieve it dynamically when necessary is a notable advantage of Lakehouse when managing MySQL historical data […]

MySQL binlog | Laravel exception handling | WordPress plugin context | MySQL GUIs. OpenLampTech is a media and content source for MySQL, PHP, and the LAMP stack.

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Freelance web developer Phil Kurth shares a fantastic developer interview with the OpenLampTech newsletter readers.

The Newsletter for PHP and MySQL Developers

Receive a copy of my ebook, “10 MySQL Tips For Everyone”, absolutely free when you subscribe to the OpenLampTech newsletter.

Phil Kurth works with a wide range of clients and builds WordPress plugin extensions for the ever-popular Advanced Custom Fields plugin.

Phil has a lot of knowledge, insight, and experience in the web development industry so I’m very excited he agreed to share this information (and more) with the OpenLampTech newsletter readers.

And now without any further ado, on to the interview.

Which is faster: LIMIT 1 or LIMIT 20? Presumably, fetching less rows is faster than fetching more rows. But for 16 years (since 2007) the MySQL query optimizer has had a “bug”† that not only makes LIMIT 1 slower than LIMIT 20 but can also make the former a table scan, which tends to cause problems. This happened last week where I work, and although MySQL DBAs are familiar with this bug, I’m writing this blog post for developers to more clearly illustrate and explain what’s going on and why because it’s really counterintuitive.

Which is faster: LIMIT 1 or LIMIT 20? Presumably, fetching less rows is faster than fetching more rows. But for 16 years (since 2007) the MySQL query optimizer has had a “bug”† that not only makes LIMIT 1 slower than LIMIT 20 but can also make the former a table scan, which tends to cause problems. This happened last week where I work, and although MySQL DBAs are familiar with this bug, I’m writing this blog post for developers to more clearly illustrate and explain what’s going on and why because it’s really counterintuitive.

Which is faster: LIMIT 1 or LIMIT 20? Presumably, fetching less rows is faster than fetching more rows. But for 16 years (since 2007) the MySQL query optimizer has had a “bug”† that not only makes LIMIT 1 slower than LIMIT 20 but can also make the former a table scan, which tends to cause problems. This happened last week where I work, and although MySQL DBAs are familiar with this bug, I’m writing this blog post for developers to more clearly illustrate and explain what’s going on and why because it’s really counterintuitive.

Last week, from November 21 to 24, the DOAG Conference took place in Nuremberg, Germany.

The MySQL Team was present at the Oracle booth. I attended the conference Thursday and Friday.

There were 20 sessions tagged “MySQL” and one full day workshop dedicated to students. I delivered the first part of the workshop dedicated to MySQL for Developers, DBAs and Ops. My colleague Carsten who attended the full week, delivered the second part of the workshop dedicated to the MySQL offer in OCI: MySQL HeatWave and LakeHouse.

The first day was a special “theme” day about Open Source Databases and other topics. Colin Charles talked about MySQL Security, Raphael Salguero presented the differences between Oracle Database, PostgreSQL and MySQL.

There were also presentations about MySQL Clustering and HA from Matthias Jung and future …

Last week, from November 21 to 24, the DOAG Conference took place in Nuremberg, Germany. The MySQL Team was present at the Oracle booth. I attended the conference Thursday and Friday. There were 20 sessions tagged “MySQL” and one full day workshop dedicated to students. I delivered the first part of the workshop dedicated to […]

MySQL Invisible Columns | Lightweight Linux distros | 10 PHP libraries for 2023 | New WooCommerce install default blocks. OpenLampTech is a media and content source for PHP, MySQL, and the LAMP stack.

The Newsletter for PHP and MySQL Developers

Receive a copy of my ebook, “10 MySQL Tips For Everyone”, absolutely free when you subscribe to the OpenLampTech newsletter.

Thank you for reading OpenLampTech. If you are not yet subscribed, be sure and grab a free subscription today.

Thank you for reading this post. Please share it with someone else who would enjoy it as well.

…

Introduction In this article, we are going to see how Index Selectivity works in relational database systems and why the database Optimizer might choose to avoid using an index if the number of matching records is large. Index selectivity is inversely proportional to the number of index entries matched by a given value. So, a unique index has the highest selectivity because only a single entry can be matched by any given value. On the other hand, if column values are skewed, then a column value matching a large number of table... Read More

The post Index Selectivity appeared first on Vlad Mihalcea.