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PostgreSQL ERROR: permission denied for schema public
In PostgreSQL 15, a fundamental change took place which is relevant to every user who happens to work with permissions: The default permissions of the public schema have been modified. This is relevant because it might hurt you during application deployment. You need to be aware of how it may affect you. Creating users Many […]
EXPLAIN that parameterized statement in PostgreSQL!
© Laurenz Albe 2022 For detailed query performance analysis, you need EXPLAIN (ANALYZE, BUFFERS) output for an SQL statement. With a parameterized statement, it can be difficult to construct a run-able statement for EXPLAIN (ANALYZE). Sometimes, you don’t even know the parameter values. I’ll show you how you can get at least plain EXPLAIN output […]
Rewrite OR to UNION in PostgreSQL queries
Rewriting OR is not always the best solution © Laurenz Albe 2022 In my article that reviles OR, I showed how in certain cases, it is possible to rewrite OR in a WHERE condition to a longer query with UNION that can perform much better (the “ugly” OR). Now people have asked me repeatedly why […]
btree vs. BRIN: 2 options for indexing in PostgreSQL data warehouses
Indexing is the key to good performance. However, people often ask: Is there an alternative to btree indexing? Can we make indexes in PostgreSQL smaller? Can we create indexes in PostgreSQL faster? And how can we index in a data warehouse? This blog will answer all those questions and show which options you have to […]
PostGIS: Upgrade GEOS with Ubuntu in 3 Steps
Many blog posts deal with installing or upgrading PostGIS. Today we’ll talk about upgrading related libraries such as GEOS or GDAL. Since PostGIS’ functionality stack relies heavily on these libraries, downloading current library versions is unavoidable; you want to use the latest stunning spatial features. Unfortunately, not all repositories serve PostGIS with the latest libraries. […]
Why are my PostgreSQL updates getting slower?
© Laurenz Albe 2022 Recently, a customer asked me why a bulk load into a PostgreSQL table kept slowing down as time went by. They saw that it was a trigger on the table that took longer and longer, and in that trigger, the updates were getting slower all the time. Now slow updates are […]
pgbouncer: Types of PostgreSQL connection pooling
pgbouncer is one of the most widely used tool for connection pooling. At CYBERTEC, we’ve successfully deployed it in many different situations. It has proven to be reliable as well as useful. Before we dive into different pooling modes and their implications, why do we need a connection pooler in the first place? The reason […]
VACUUM does not shrink my PostgreSQL table
Did you ever wonder why VACUUM does not make your PostgreSQL tables smaller? Did you ever wonder why VACUUM does not shrink data files? Well, maybe this is the article you have been looking for. The point is: usually, space is not returned to the operating system after a cleanup and it is important to […]
LISTEN / NOTIFY: Automatic client notification in PostgreSQL
What is LISTEN and NOTIFY? LISTEN / NOTIFY is a feature that enables users to listen to what goes on in the database. It is one of the oldest functionalities in PostgreSQL and is still widely used. The main question is: What is the purpose of the asynchronous query interface (LISTEN / NOTIFY), and what […]
PostgreSQL: Sequences vs. Invoice numbers
Sequences are a core feature of SQL. However, some users are tempted to implement sequences to generate invoices. That’s dangerous and should be avoided. The core question is: Why? What’s the problem with using database-side sequences to put unique invoice numbers to send to clients? Let’s dive in and find out. Getting started with CREATE […]
What is an inner join in SQL? And what is an outer join?
A join is a concept in IT which is widely used and often referred to but rarely really understood. What are the differences between inner joins, outer joins, semi joins and so on? Let’s shed some light on them and see how inner and outer joins really work. Producing sample data Before we can get […]
ERROR: nextval: reached maximum value of sequence
serial is a popular pseudo data type in PostgreSQL which is often used to generate auto-increment columns. However, this can lead to issues which are often underestimated. So what is the problem? Some of you might have already seen the following error message in real life: What happened here is that the underlying integer column […]