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How slow is SELECT * ?

Pubblicato il 18 Settembre 2021 da Federico Razzoli — Nessun commento ↓

<img width="600" height="311" src="https://vettabase.com/blog/wp-content/uploads/2021/09/select_star.png" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/09/select_star.png 600w, https://vettabase.com/blog/wp-content/uploads/2021/09/select_star-300x156.png 300w, https://vettabase.com/blog/wp-content/uploads/2021/09/select_star-16x8.png 16w" sizes="(max-width: 600px) 100vw, 600px" />

The most widely known query optimisation rule is that developers should always avoid SELECT *. Even when all columns are needed, they should list their names, because more columns could be created in the future. But developers find this really Continua a leggere How slow is SELECT * ?→

Identify useless queries in MariaDB/MySQL

Pubblicato il 7 Settembre 2021 da Federico Razzoli — Nessun commento ↓

<img width="600" height="237" src="https://vettabase.com/blog/wp-content/uploads/2021/09/identify_useless_queries.png" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/09/identify_useless_queries.png 600w, https://vettabase.com/blog/wp-content/uploads/2021/09/identify_useless_queries-300x119.png 300w, https://vettabase.com/blog/wp-content/uploads/2021/09/identify_useless_queries-16x6.png 16w" sizes="(max-width: 600px) 100vw, 600px" />

Some queries always fail or never return rows. They should be eliminated to improve database performance. Continua a leggere Identify useless queries in MariaDB/MySQL→

NULL comparisons in MariaDB, PostgreSQL, and SQLite

Pubblicato il 6 Settembre 2021 da Federico Razzoli — Nessun commento ↓

<img width="600" height="311" src="https://vettabase.com/blog/wp-content/uploads/2021/09/null_comparisons-1.png" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/09/null_comparisons-1.png 600w, https://vettabase.com/blog/wp-content/uploads/2021/09/null_comparisons-1-300x156.png 300w, https://vettabase.com/blog/wp-content/uploads/2021/09/null_comparisons-1-16x8.png 16w" sizes="(max-width: 600px) 100vw, 600px" />

Comparisons are tricky when NULL values are involved. But some databases offer some special, handy syntax to solve the problem. Continua a leggere NULL comparisons in MariaDB, PostgreSQL, and SQLite→

Choosing Cassandra consistency levels

Pubblicato il 9 Agosto 2021 da Federico Razzoli — 2 commenti ↓

<img width="600" height="311" src="https://vettabase.com/blog/wp-content/uploads/2021/08/cassandra_choose_consistency_level.jpeg" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/08/cassandra_choose_consistency_level.jpeg 600w, https://vettabase.com/blog/wp-content/uploads/2021/08/cassandra_choose_consistency_level-300x156.jpeg 300w, https://vettabase.com/blog/wp-content/uploads/2021/08/cassandra_choose_consistency_level-16x8.jpeg 16w" sizes="(max-width: 600px) 100vw, 600px" />

Choose the best balance between speed and consistency by setting proper consistency levels. Continua a leggere Choosing Cassandra consistency levels→

ALERT: Many Cassandra users may need an urgent upgrade

Pubblicato il 28 Luglio 2021 da Federico Razzoli — Nessun commento ↓

<img width="446" height="300" src="https://vettabase.com/blog/wp-content/uploads/2021/06/hours_smaller.jpeg" class="attachment-featured-slider size-featured-slider wp-post-image" alt="Vettabase Monthly Time" srcset="https://vettabase.com/blog/wp-content/uploads/2021/06/hours_smaller.jpeg 446w, https://vettabase.com/blog/wp-content/uploads/2021/06/hours_smaller-300x202.jpeg 300w, https://vettabase.com/blog/wp-content/uploads/2021/06/hours_smaller-16x12.jpeg 16w" sizes="(max-width: 446px) 100vw, 446px" />

Vettabase Monthly Time

Cassandra 4.0 GA was released on 26th July 2021. Older versions users need to upgrade quickly. Continua a leggere ALERT: Many Cassandra users may need an urgent upgrade→

Automating interactive programs execution with Expect

Pubblicato il 13 Luglio 2021 da Federico Razzoli — Nessun commento ↓

<img width="640" height="318" src="https://vettabase.com/blog/wp-content/uploads/2021/07/automate_interactive_programs_with_expect-640x318.jpeg" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/07/automate_interactive_programs_with_expect-640x318.jpeg 640w, https://vettabase.com/blog/wp-content/uploads/2021/07/automate_interactive_programs_with_expect-16x8.jpeg 16w" sizes="(max-width: 640px) 100vw, 640px" />

How we automated the creation of immudb users and databases with the help of the Expect language. Continua a leggere Automating interactive programs execution with Expect→

Cassandra login error: Cannot achieve consistency level LOCAL_ONE

Pubblicato il 9 Luglio 2021 da Federico Razzoli — Nessun commento ↓

<img width="640" height="318" src="https://vettabase.com/blog/wp-content/uploads/2021/07/cassandra_cannot_achieve_local_one-640x318.jpeg" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/07/cassandra_cannot_achieve_local_one-640x318.jpeg 640w, https://vettabase.com/blog/wp-content/uploads/2021/07/cassandra_cannot_achieve_local_one-16x8.jpeg 16w" sizes="(max-width: 640px) 100vw, 640px" />

Cassandra login fails with: “Cannot achieve consistency level LOCAL_ONE”? Let’s see why it happens, and how to solve the problem Continua a leggere Cassandra login error: Cannot achieve consistency level LOCAL_ONE→

Populating tables faster in PostgreSQL

Pubblicato il 9 Luglio 2021 da Michael Aboagye — Nessun commento ↓

<img width="600" height="291" src="https://vettabase.com/blog/wp-content/uploads/2021/09/postgresql_populate_tables_faster-1.png" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/09/postgresql_populate_tables_faster-1.png 600w, https://vettabase.com/blog/wp-content/uploads/2021/09/postgresql_populate_tables_faster-1-300x146.png 300w, https://vettabase.com/blog/wp-content/uploads/2021/09/postgresql_populate_tables_faster-1-16x8.png 16w" sizes="(max-width: 600px) 100vw, 600px" />

Fast-loading rows into a PostgreSQL table using the COPY FROM command. Continua a leggere Populating tables faster in PostgreSQL→

A summary of MariaDB 10.6

Pubblicato il 7 Luglio 2021 da Federico Razzoli — Nessun commento ↓

<img width="640" height="318" src="https://vettabase.com/blog/wp-content/uploads/2021/07/upgrade_to_mariadb_10_6-640x318.jpeg" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/07/upgrade_to_mariadb_10_6-640x318.jpeg 640w, https://vettabase.com/blog/wp-content/uploads/2021/07/upgrade_to_mariadb_10_6-16x8.jpeg 16w" sizes="(max-width: 640px) 100vw, 640px" />

MariaDB 10.6 is now Generally Available! Let’s see what’s new and if it’s worth an upgrade. Continua a leggere A summary of MariaDB 10.6→

Tuning Linux kernel for PostgreSQL

Pubblicato il 19 Giugno 2021 da Michael Aboagye — Nessun commento ↓

<img width="600" height="314" src="https://vettabase.com/blog/wp-content/uploads/2021/06/tuning_linux_for_postgresql.jpeg" class="attachment-featured-slider size-featured-slider wp-post-image" alt="" srcset="https://vettabase.com/blog/wp-content/uploads/2021/06/tuning_linux_for_postgresql.jpeg 600w, https://vettabase.com/blog/wp-content/uploads/2021/06/tuning_linux_for_postgresql-300x157.jpeg 300w, https://vettabase.com/blog/wp-content/uploads/2021/06/tuning_linux_for_postgresql-16x8.jpeg 16w" sizes="(max-width: 600px) 100vw, 600px" />

Learn how to tune Linux parameters to improve PostgreSQL performance and reliability. Continua a leggere Tuning Linux kernel for PostgreSQL→