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© Laurenz Albe 2025

Saving storage space should not be your first objective in a PostgreSQL database. Very often, the desire to conserve space aggressively comes at the expense of performance. But there is also no reason to needlessly waste space. Therefore, it is a good idea to be familiar with the concepts of data type alignment and padding bytes in PostgreSQL.

And we’re back.

PostgreSQL 18 changes this week

With all five CommitFests over, we're now into the testing and bugfix phase, and no new features are likely to be added. Having said that, there have been a few tweaks to SQL function performance and handling this week.

April 9 Christoph Berg spoke at the Postgres Extensions Ecosystem Mini-Summit #3 (slides, recording, transcript), a series of virtual events leading up to the gathering at PGConf.Dev.

April 2nd the Talking Postgres podcast airs live, with Claire Giordano as the host, Bruce Momjian as the guest, and Aaron Wislang as its producer.

Henrietta Dombrovskaya kicked off Prairie Postgres, with help from Pat Wright, Dian Fay and Anna Bailliekova.

Gülçin Yıldırım Jelínek organized the [Prague PostgreSQL Meetup, March Edition on March 31st]((https://www.meetup.com/prague-postgresql-meetup/events/306440481). Mayuresh B and Tomáš Vondra presented sessions.

Nordic PGDay (March 18) was organized by Daniel Gustafsson, Magnus Hagander, Georgios Kokolatos.

The following speakers contributed with a talk:

PostgreSQL Person of the week: Emma Saroyan

... Thanks Andreas Scherbaum, for publishing these interviews since - checks notes - February 2020!

I wrote an article about PostgreSQL 18.  It is in Czech language, but translators from Czech to English, German, ... works relatively well today.

 https://www.root.cz/clanky/postgresql-18-tricet-let-otevreneho-vyvoje-databaze/

On 5th of April 2025, Álvaro Herrera committed patch: Add modern SHA-2 based password hashes to pgcrypto.   This adapts the publicly available reference implementation on https://www.akkadia.org/drepper/SHA-crypt.txt and adds the new hash algorithms sha256crypt and sha512crypt to crypt() and gen_salt() respectively.

Just a quick note to users of pgenv and anyone else who compiles Postgres on macOS. In macOS 15.4, Apple introduced a new API, strchrnul, which is common from other platforms. As a result attempting to compile Postgres on 15.4 and later will lead to this error:

Postgres does a great job of making queries really efficient. By gathering data in internal statistics tables, Postgres estimates before a query is run lots of things - like will an index scan be better than a sequential scan. How to pull data for the WHERE statement.

I wrote User, User, Who Is the User? in January of 2024, but didn't publish the slides at that time. I was planning to publish them once I delivered the presentation, but it has been a year and I have still not deivered the talk, so I am now publishing the slides.

On 4th of April 2025, Andrew Dunstan committed patch: Non text modes for pg_dumpall, correspondingly change pg_restore   pg_dumpall acquires a new -F/--format option, with the same meanings as pg_dump. The default is p, meaning plain text. For any other value, a directory is created containing two files, globals.data and map.dat.

Performance optimization in a production database is important, but trying to over-optimize can make things more complicated without real improvements.

In this post, I’ll share two very basic EXPLAIN ANALYZE outputs from a production system. A user asked us to help optimize these queries. I've changed the table and column names for privacy. We will look at how to spot slow parts of a query, improve performance the right way, and avoid unnecessary tuning.

Plan A: Identifying and Resolving a Bottleneck

In the previous post we have imported a fairly large data set containing Wikipedia data, which we downloaded using pgai. However, importing all this data is not enough because we also need to keep an eye on efficiency. Therefore, it is important to understand that indexing is the key to success.

In general, pgvector provides us with two types of indexes that we can use:

- hnsw
- ivfflat

Last week Christoph Berg, who maintains PostgreSQL’s APT packaging system, gave a very nice talk on that system at the third PostgreSQL Extension Mini-Summit.

 Way back in PostgreSQL 9.5, there was a simple entry in the release notes:

Improve PL/pgSQL array performance (Tom Lane)

We are proud of what we have done in Bolzano.

PgTraining OpenDay is over!

Last Friday was PgTraining OpenDay in Bolzano, a free of charge day entirely dedicated to PostgreSQL, that we at PgTraning organized.

Well, the code freeze has come and gone, so it's all over for PostgreSQL 18 development, bar the testing. RC1 is likely due at the start of September, so fire up those test environments sooner rather than later!

Any new features from here on out will be for the future PostgreSQL 19 , whose first CommitFest will start in July ( 2025-07 ).