© Laurenz Albe 2023 Different from many other database systems, PostgreSQL does not support query hints. That makes it difficult to force the hand of the query planner when it comes to a certain join order that you know to be good. This article explains how you can influence execution plans in PostgreSQL. Why no […]

© Laurenz Albe 2023 A while ago, I wrote about how difficult it is to get an execution plan for a parameterized query. The method suggested in that article works, but is still somewhat complicated. So I wrote a patch to support an EXPLAIN option GENERIC_PLAN, which provides native support for that. My patch got […]

What is a parallel aggregate? In PostgreSQL, a parallel aggregate refers to a way of processing aggregate functions (such as SUM, AVG, MAX, MIN, etc.) on large amounts of data in a parallel and distributed manner, thereby making the query execution faster. When executing an aggregate query, the database system automatically breaks up the result […]

© Laurenz Albe 2023 The PostgreSQL documentation has some information about row locks. But typically, you cannot see them in pg_locks, and not everybody knows how they work and how to track and debug row locks. This article intends to give some insight into how PostgreSQL row locks work “under the hood”. Why are there […]

Data isn’t only about storage and accumulation – sometimes it’s also about deletion, cleanup and archiving. In SQL there’s more than one way to empty a table. Two essential methods are available: DELETE TRUNCATE DELETE vs. TRUNCATE Both commands serve totally different purposes, which are sometimes not fully understood. The key difference is that DELETE […]

© Laurenz Albe 2022 When processing a big result set in an interactive application, you want to paginate the result set, that is, show it page by page. Everybody is familiar with that from the first web search on. You also get a button to scroll to the next page, and you get a total […]

Analyzing time series often comes with challenges. This is especially true if you want to do a bit more than just run simple counts on values in a column. More often than not you’ll want to create a month’s report, a weekly overview and so on. This requires you to group on expressions rather than […]

As of version 15, PostgreSQL offers you the ability to write the server log in JSON format. This feature has been desired for a long time and has finally made it to PostgreSQL core. In this post we will discuss how JSON logs can be configured and what this brand new feature does for users. […]

© Laurenz Albe 2022 A while ago, I wrote about the performance impact of query parameter data types. Recently I encountered a similar problem with UNION ALL that baffled me for a while, so I’d like to share it with you. UNION ALL to implement polymorphism Different entities can have something in common. For example, […]

What is pg_dump compression? pg_dump is a PostgreSQL utility for backing up a local or remote PostgreSQL database. It creates a logical backup file that contains either plain SQL commands for recreating the database, or a binary file that can be restored with the pg_restore utility. The binary backup file can be used to restore […]

While the term faceting may sound foreign to you, you almost certainly have run into it in your adventures online. It is those helpful little boxes that turn up when browsing in web shops or searching in catalogs, telling how to further narrow down the search results, (for example, by color) and how many items […]

© 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 […]