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 […]
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 […]
How to corrupt your PostgreSQL database
Of course most people do not want to corrupt their databases. These people will profit from avoiding the techniques used in this article. But for some, it might be useful to corrupt a database, for example if you want to test a tool or procedure that will be used to detect or fix data corruption. […]
Better SQL functions in PostgreSQL v14
We all know and value SQL functions as a handy shortcut. PostgreSQL v14 has introduced a new, better way to write SQL functions. This article will show the advantages of the new syntax. An example of an SQL function Let’s create a simple example of an SQL function with the “classical” syntax so that we […]
Transaction anomalies with SELECT FOR UPDATE
© Laurenz Albe 2022 I was recently confronted with a nice example of how adding FOR UPDATE to a query can introduce transaction anomalies. This article will explain how that happens and how you can cope with the problem. Be ready to learn some PostgreSQL implementation details! The example Setting the stage We have a […]
Debugging deadlocks in PostgreSQL
© Laurenz Albe 2022 Even if you understand what a deadlock is, debugging deadlocks can be tricky. This article shows some techniques on how to figure out the cause of a deadlock. A simple deadlock example Setting the stage We will test our techniques for debugging deadlocks with the following example: The deadlock To provoke […]
Case-insensitive pattern matching in PostgreSQL
© Renée Albe 2022 Case-insensitive search is a much-requested feature, partly (I suspect) to maintain compatibility with Microsoft SQL Server. There are several solutions to the problem, one of which is to use case-insensitive ICU collations. This works like a charm, except if you want to perform pattern matching. So let’s have a closer […]
View permissions and row-level security in PostgreSQL
© Laurenz Albe 2022 The details of how view permissions are checked have long puzzled me. PostgreSQL v15 introduces “security invoker” views, which change how permissions are checked. The new security invoker views make it possible to use row-level security effectively. I’ll use this opportunity to explain how view permissions work and how you can […]
Help, I cannot cancel a PostgreSQL query!
© Laurenz Albe 2022 Sometimes a PostgreSQL query takes forever. Usually, it is easy to interrupt (cancel) such a statement, but sometimes it can turn into a problem, and a query cannot be canceled. This article discusses what might be the cause. I’ll also show you a trick how to solve the problem (not for […]
Time zone management in PostgreSQL
© Laurenz Albe 2022 Next to character encoding, time zones are among the least-loved topics in computing. In addition, PostgreSQL’s implementation of timestamp with time zone is somewhat surprising. So I thought it might be worth to write up an introduction to time zone management and recommendations for its practical use. Time zones and the […]
How to DROP ROLE or DROP USER in PostgreSQL
© Laurenz Albe 2022 You might, at first glance, believe that DROP ROLE (or DROP USER, which is the same) is a simple matter. However, that’s not always the case. So I thought it might be a good idea to show you the problems involved and how to solve them. Why is there no DROP […]