Tag: postgresql
WITH HOLD cursors and transactions in PostgreSQL
© Laurenz Albe 2021 Both cursors and transactions are basic ingredients for developing a database application. This article describes how cursors and transactions interact and how WITH HOLD can work around their limitations. We will also see the dangers involved and how to properly use WITH HOLD cursors in a PL/pgSQL procedure. Cursors in PostgreSQL […]
Gaps in sequences in PostgreSQL
© Laurenz Albe 2021 Most database tables have an artificial numeric primary key, and that number is usually generated automatically using a sequence. I wrote about auto-generated primary keys in some detail in a previous article. Occasionally, gaps in these primary key sequences can occur – which might come as a surprise to you. This […]
JSON in PostgreSQL: how to use it right
© Laurenz Albe 2021 The comprehensive JSON support in PostgreSQL is one of its best-loved features. Many people – particularly those with a stronger background in Javascript programming than in relational databases – use it extensively. However, my experience is that the vast majority of people don’t use it correctly. That causes problems and unhappiness […]
PostgreSQL schedulers: comparison table
Hello, my name is Pavlo Golub, and I am a scheduler addict. That began when I implemented pg_timetable for PostgreSQL. I wrote a lot about it. In this post, I want to share the result of my investigations on the schedulers available for PostgreSQL. I gave a talk about this topic at the CERN meetup, so […]
Index bloat reduced in PostgreSQL v14
© Laurenz Albe 2021 PostgreSQL v12 brought more efficient storage for indexes, and v13 improved that even more by adding deduplication of index entries. But Peter Geoghegan is not done yet! PostgreSQL v14 will bring “bottom-up” index entry deletion, which is targeted at reducing unnecessary page splits, index bloat and fragmentation of heavily updated indexes. […]
PostGIS upgrade with Ubuntu 20.04.02
Last time, we installed PostGIS on top of PostgreSQL. Today, I will complement this article by describing how someone can upgrade PostGIS on Ubuntu. A detailed description can be found at postgis.net and should be referred to in parallel. Let me first define our scenario and goal: An artificial customer wants his PostGIS-enabled PostgreSQL 13 […]
Fixing out-of-sync sequences in PostgreSQL
Creating auto increment columns in PostgreSQL is easy. Simply use two pseudo data types serial and serial8, respectively, then PostgreSQL will automatically take care of your auto increment columns. However, once in a while problems can still occur. Let us take a look and see. Sequences: Avoid manual values To understand the underlying problem, one […]
PostgreSQL vs Redis vs Memcached performance
When I recently stumbled on an article comparing some main properties, and also the read-write performance of two very popular pieces of caching software, often used to speed up applications heavy on database queries, I immediately felt an itch – how would it actually look for PostgreSQL vs Redis vs Memcached on the performance side? […]
From MD5 to scram-sha-256 in PostgreSQL
© Laurenz Albe 2021 Since v10, PostgreSQL has provided support for scram-sha-256 for password hashing and authentication. This article describes how you can adapt your application safely. Why do we need scram-sha-256? PostgreSQL uses cryptographic hashing for two purposes: The actual database password is a hash of the clear text password entered by the user. […]
Disabling autocommit in PostgreSQL can damage your health
© Laurenz Albe 2021 When analyzing customer’s problems, I have seen the mess you can get into if you disable autocommit in your interactive client, so I’d like to bring this topic to a wider audience. What is autocommit? In PostgreSQL, like in any other ACID-complicant database, each statement runs in a transaction: if the […]
How to interpret PostgreSQL EXPLAIN ANALYZE output
© Laurenz Albe 2021 EXPLAIN ANALYZE is the key to optimizing SQL statements in PostgreSQL. This article does not attempt to explain everything there is to it. Rather, I want to give you a brief introduction, explain what to look for and show you some helpful tools to visualize the output. How to call EXPLAIN […]
PostgreSQL: Bulk loading huge amounts of data
Bulk loading is the quickest way to import large amounts of data into a PostgreSQL database. There are various ways to facilitate large-scale imports, and many different ways to scale are also available. This post will show you how to use some of these tricks, and explain how fast importing works. You can use this […]