I am officially open to new international opportunities! 🌍

3 June 2026:

After a temporary stay in Japan to focus on my health and personal responsibilities, I am fully recovered, ready, and excited to work abroad again.

I am highly interested in returning to Europe, as well as opportunities in the Southern Hemisphere and Southeast Asia.

Looking for:

  • Challenging tasks in PostgreSQL.
  • Roles offering international visa sponsorship OR Remote work that supports a digital nomad lifestyle.

If your team is hiring, let’s connect! Please feel free to reach out via e-Mail(hironobu @ interdb.jp or interdb.mx @ gmail.com) or DM.

What’s New
DateDescription
1 June 2026 Added Section 3.4.3 Constraints.
27 May 2026 Updated Chapter 8 to focus on version 9.6 and later, removing deprecated content for version 9.5 and older.
25 May 2026 Fixed an error in Section 8.4.2 by correcting the sequence of Steps (5) and (6), along with Figure 8.9.
23 May 2026 Refactor all chapters: reduced by 4,890 words (5.6%).
11 May 2026 Added Section 1.3.2 TOAST (The Oversized-Attribute Storage Technique).
1 May 2026 Added Chapter 12: Logical Replication (Beta Version).
27 Oct 2025 Improved the explanation in Section 8.6.
09 Oct 2025 Added the explanation about Cardinality Estimation in Section 3.2.4.
15 Apr 2025 Added the explanation about pg_stat_progress_vacuum view in Section 6.1.
15 Dec 2024 Added Section 9.5.1.
14 Dec 2024 Added the explanation about Conflicts in Section 11.2.4.
13 Dec 2024 Added Replication Slots in Section 11.4.
5 Dec 2024 Added the explanation about Sharing the Ring Buffer with Two Backends in Section 8.5.1.
4 Dec 2024 Added Local Buffer Management in Section 8.5.2.
1 Dec 2024 Added Quorum-Based Synchronous Replication in Section 11.3.2.1.
30 Nov 2024 Corrected an error in the Checkpoint explanation.
In the checkpoint sequence described in Section 9.7.1, the timing of the checkpoint WAL record write has been moved from step (2) to step (4).
28 Nov 2024 Added 3.7. Parallel Query.
24 Nov 2024 Added 3.4.2. Aggregate Functions.
Improved 3.4.1. How the Executor Performs.
28 Oct 2024 Added the descriptions of Incremental Backup:
04 Jan 2024 Changed framework from Cascade to Relearn.
11 Sep 2023 Updated Sections 8.2.2 and 8.3.2.
Although the original text was based on version 9.5, these sections have been updated based on versions 9.6 or later due to the significant changes made to the BufferDesc structure in version 9.6.
02 Aug 2023 Fixed bug in Section 5.9.
CheckTargetForConflictsIn -> CheckForSerializableConflictIn
CheckTargetForConflictsOut -> CheckForSerializableConflictOut
02 Aug 2023 Added "Conditions for autovacuum to run" in Section 6.5.1 and "Maintenance tips" in Section 6.5.2.
02 May 2023 Splitted Chapter 3 in three files since this part was too long.
24 Feb 2023 Removed "9.9.3. WAL Segment Management in Version 9.4 or Earlier" in Section 9.9.
12 Jan 2023 Changed txid_current_snapshot() to pg_current_snapshot() in Section 5.5.
22 Oct 2022 Added "archive_library" in Section 9.10.
22 Oct 2022 Updated function names:pg_backup_start and pg_backup_stop in Chapter 10.
02 Jan 2022 Added "WAL, Backup, and Replication" in Section 9.1.3.
12 Nov 2021 Changed the description in the preface of Chapter 5.
  • Concurrency Control is a mechanism that maintains consistency atomicity and isolation,...
25 Mar 2021 Added a command to delete archiving logs in Section 9.10.
28 Jun 2020 Changed the color scheme of the all figures.
19 Jun 2020 Added Section 3.5.3.3.
06 Jun 2020 Updated the table 4.1 in Section 4.2.
Added "PARALLEL option" in Section 6.1.
Added the description about the "cleaning up indexes" phase in Section 6.1.
04 Jun 2020 Added a description related to recovery.conf in Section 10.2.
27 Mar 2019 Added "Indexes Internals" in Section 1.4.2.
15 Dec 2018 Fixed Section 3.3.2.1.
  • Based on the cheapest access path obtained here, a query tree a plan tree is generated.
10 Oct 2018 Improved Section 8.1.2.
01 Oct 2018 Fixed Section 3.3.2.2.
  • (3) Create a path, estimate the cost of the sequential scan and add the path to the indexlist pathlist of the RelOptInfo.
24 Aug 2018 Added Section 4.1.
13 Aug 2018 Changed in Section 9.7.
13 Aug 2018 Added "How to Maintain AUTOVACUUM" in Section 6.5.
03 Aug 2018 Added "Why the checkpointer was separated from the background writer?" in Section 8.6.
3 Jun 2018 Updated for Version 11.
  1. Updated Section 6.1.1.
  2. Added "WAL segment file size" in Section 9.2.
  3. Added "Removal of prior checkpoint in PostgreSQL 11" in Section 9.7.2.
  4. Updated Section 9.9.2.
  5. Updated Section 10.1.1.

The Internals of PostgreSQL

PostgreSQL is a well-designed, open-source multi-purpose relational database system which is widely used throughout the world.

It is one huge system with the integrated subsystems, each of which has a particular complex feature and works cooperatively with each other. Although understanding of the internal mechanism is crucial for both administration and integration using PostgreSQL, its hugeness and complexity make it difficult.

The main purposes of this documentation are to explain how each subsystem works, and to provide the whole picture of PostgreSQL.

This documentation covers versions 18 and earlier.

Some academic papers have referred to this documentation. The Chinese version of this documentation was published in June 2019.

This documentation was first published on 26 September 2015.

Contents

Author

Hironobu SUZUKI

I am a software programmer/engineer, the author of:

I graduated from graduate school in information engineering (M.S. in Information Engineering), have worked for several companies as a software developer and technical manager/director. I published seven books in the fields of database and system integration (4 PostgreSQL books and 3 MySQL books). In June 2019, the Chinese book of this documentation was published.

As a director of the Japan PostgreSQL Users Group (2010-2016), I organized the largest (non-commercial) technical seminar/lecture on PostgreSQL in Japan for more than six years, and also served as the program committee chair of the Japan PostgreSQL Conference in 2013 and as a member in 2008 and 2009.

In June 2022, my interview article was published in “PostgreSQL person of the week”.

Cuando era joven, vivió en Sudamérica por unos años. Recientemente, a veces vuelve a allí.

I am seeking a remote position focused on the application of ML and AI technologies to DBMS. For personal reasons, I will be living in Japan for several years.

      Blog

Contact

Please read the following FAQ before sending messages.

Since publishing my content, I’ve been fortunate to receive a lot of positive feedback, which is truly gratifying. However, unfortunately, I’ve encountered individuals in the past who tried to misuse my content for self-promotion 1.

These experiences have shaped the approach I’ve outlined below.

  1. Who can use this documentation freely?
    If you are a teacher or a student belonging to an educational organization, you can freely use this documentation and figures in your study. Anyone can use this documentation and figures with noncommercial meetings and lectures, if you state the link to this site and the copyright; otherwise, contact me.
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    This content can be used under two options:
    There was a comment on Hacker News that took this seriously, but of course, it’s a joke. To be clear, I have no intention of having any commercial ties to this. Regardless, you can imagine the kind of requests I get on a daily basis.
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    No. I am writing for my own enjoyment. Even if you send me your article, I will never include it in my documentation.
  4. Why doesn’t the author use the GitBook or other e-book formats/sites?
    I am using the best tools I need and I will decide what I use. I am always trying a lot of tools for better explanations.
    Simply put, this documentation is optimized to read on html file and it is hard to convert to other formats.
    I do not have any plan to make PDF version and Smartphone versions because of same reason.
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    I keep my domain and my server to provide my documentation; you can read when you want to read. What do you want more?
  6. Why doesn’t the author waive the copyright of this documentation or use the creative commons license?
    I’d like to ask you what problems you have by that I keep on having the copyright of my documentation.

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