feat: recipe 23 - pgvector and postgis extension

Signed-off-by: Gabriele Bartolini <[email protected]>

Author: gbartolini

content/posts/20251201-extensions/cover.jpg

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+---
+title: "CNPG Recipe 23 - Managing extensions with ImageVolume in CloudNativePG"
+date: 2025-12-01T21:35:11+01:00
+description: "Leveraging the Kubernetes `ImageVolume` feature and PostgreSQL 18's `extension_control_path`, this article demonstrates the CloudNativePG method for declaratively managing extensions like `pgvector` and PostGIS from separate container images, marking the culmination of a multi-year vision to decouple the database core from extension distribution."
+tags: [ "postgresql", "kubernetes", "cloudnativepg", "pgvector", "postgis", "imagevolume", "declarative", "extensions", "immutability", "postgres18", "operator", "database", "cnpg", "dok", "extension_control_path" ]
+cover: cover.jpg
+thumb: thumb.jpg
+draft: false
+---
+
+_Say goodbye to the old way of distributing Postgres extensions as part of the
+main pre-built operand image. Leveraging the Kubernetes `ImageVolume` feature,
+CloudNativePG now allows you to mount extensions like `pgvector` and
+PostGIS from separate, dedicated images.
+This new declarative method completely decouples the PostgreSQL core from the
+extension binaries, enabling dynamic addition, easier evaluation, and
+simplified updates without ever having to build or manage monolithic custom
+container images._
+
+<!--more-->
+
+---
+
+In a [previous post]({{< relref
+"../20250303-volume-source-extension-control-path/index.md" >}}), I made the
+case for the **immutable future of PostgreSQL extensions** on Kubernetes.
+Traditionally, achieving immutability meant building large, custom container
+images for the Postgres operand with every extension needed.
+
+Before the method I am about to show you, the common approach for extensions like
+`pgvector` was to use the `standard` CNPG image, which already came
+pre-packaged with only a few extensions—a method I detailed in my article on
+[getting started with `pgvector` on Kubernetes]({{< relref "../20250926-postgresql-18/index.md" >}}).
+
+Now, I want to show you a groundbreaking, more flexible approach that I believe
+represents the *true* future of extension management: a moment that marks the
+beginning of the end of a multi-year vision we've had at EDB and, previously,
+at 2ndQuadrant.
+
+This new flexibility is unlocked by the latest crucial steps: the combination
+of PostgreSQL 18's `extension_control_path` GUC (Grand Unified Configuration
+variable) and the Kubernetes `ImageVolume` feature. We're leveraging this with
+CloudNativePG to mount extensions from dedicated container images. Notably,
+`pgvector` and PostGIS are the first set of extension images officially
+released by the community through the [`postgres-extensions-containers` project](https://github.com/cloudnative-pg/postgres-extensions-containers).
+
+This allows us to use the small, official `minimal` PostgreSQL images while
+seamlessly integrating complex extensions like `pgvector` and PostGIS.
+
+## Prerequisites: PostgreSQL 18 and Kubernetes' `ImageVolume`
+
+Before diving into the manifests, I must stress the technical requirements for
+this approach. It relies on Kubernetes' capability to expose an entire
+container image as a volume, which CNPG then mounts into the PostgreSQL pod.
+
+This functionality requires Kubernetes 1.33 or later because it depends on the
+`ImageVolume` feature. This feature is not yet enabled by default, but it is
+expected to be generally available and enabled by default in Kubernetes 1.35
+(available this month, December 2025).
+
+If you are using Kind for your local development environment, you must
+explicitly enable this feature gate when creating your cluster, like in the
+example below:
+
+```bash
+(cat << EOF
+kind: Cluster
+apiVersion: kind.x-k8s.io/v1alpha4
+featureGates:
+  ImageVolume: true
+EOF
+) | kind create cluster --config -
+```
+
+For our demonstration, I will be using **PostgreSQL 18**.
+Note that to run these manifests, you must also have the latest stable version
+of CloudNativePG installed in your Kubernetes cluster; instructions can be
+found in the official [CloudNativePG documentation](https://cloudnative-pg.io/documentation/preview/installation_upgrade/).
+
+
+## Starting with the minimal CNPG cluster
+
+I always recommend starting simple. We begin with the most basic, lightweight
+CNPG Cluster definition. I am using the official CNPG `minimal` image for
+PostgreSQL (which I have written about previously in my piece on
+[leveraging the new CNPG supply chain and image catalogs]({{< relref "../20251006-image-catalog/index.md" >}}))
+for PostgreSQL 18 (which you can learn more about
+[running PostgreSQL 18 today on Kubernetes]({{< relref "../20250605-pgvector/index.md" >}})).
+
+This image only contains the core database binaries, with no unnecessary
+extensions or dependencies.
+
+```yaml
+{{< include "yaml/01.yaml" >}}
+```
+
+This cluster is perfectly ready to serve basic PostgreSQL operations.
+However, if you attempt to run `CREATE EXTENSION vector;` right now, the
+command will fail because the required extension control and shared object
+(`.so`) files are not present in the `minimal` base image.
+
+## Introducing `pgvector` via a dedicated image
+
+Instead of switching to a heavy, custom `imageName`, I introduce the new
+`postgresql.extensions` block. This is where the magic happens. I am
+instructing CloudNativePG to find a separate image containing the compiled
+`pgvector` binaries and mount it into the PostgreSQL container using
+`ImageVolume`.
+
+### The manifest
+
+```yaml
+{{< include "yaml/02.yaml" >}}
+```
+
+### Verification: the extension is ready
+
+Once you apply the manifests above, CloudNativePG handles both mounting the
+binary files via `ImageVolume` and running the necessary `CREATE EXTENSION`
+SQL.
+
+First, let's confirm the `pgvector` binaries have been successfully mounted
+into the pod's filesystem. I'm targeting the primary pod (assuming the name
+follows the pattern `angus-1`) and listing the contents of the
+mounted `/extensions/` directory:
+
+```bash
+kubectl exec -ti angus-1 -c postgres -- ls /extensions/
+```
+
+The output confirms the extension directory is present, mounted from the
+separate extension image:
+
+```
+pgvector
+```
+
+Next, we verify that the extension is active and ready in the `app` database:
+
+```bash
+kubectl cnpg psql angus -- app -c '\dx'
+```
+
+The output confirms the declarative process was successful:
+
+```
+                                      List of installed extensions
+  Name   | Version | Default version |   Schema   |                  Description
+---------+---------+-----------------+------------+------------------------------------------------------
+ plpgsql | 1.0     | 1.0             | pg_catalog | PL/pgSQL procedural language
+ vector  | 0.8.1   | 0.8.1           | public     | vector data type and ivfflat and hnsw access methods
+(2 rows)
+```
+
+### What I have achieved here
+
+1. `Cluster.spec.postgresql.extensions`: I have registered the `pgvector`
+   extension by referencing a specific extension image. This image holds only
+   the compiled binaries for `pgvector`.
+
+2. `ImageVolume` in action: CloudNativePG intelligently mounts the contents of
+   `ghcr.io/cloudnative-pg/pgvector:0.8.1-18-trixie` directly into the
+   PostgreSQL pod's file system, ensuring the necessary binaries are available
+   and read-only. Underneath, this is achieved by leveraging the
+   `extension_control_path` GUC, a key feature introduced in PostgreSQL 18,
+   which allows the database to locate the necessary extension control files
+   outside of the traditional installation directories.
+
+3. `Database.spec.extensions`: This resource handles the final, declarative
+   activation. I instruct PostgreSQL to run `CREATE EXTENSION vector VERSION '0.8.1';`.
+   This is key: CloudNativePG manages this command declaratively,
+   meaning I never have to connect and run SQL myself. Furthermore, the
+   `version` field is crucial; by simply applying a new image and changing this
+   value, CNPG orchestrates the PostgreSQL update path (provided the extension
+   itself supports the upgrade).
+
+This cleanly decouples the PostgreSQL core from the extension binaries,
+providing immutability without the custom image maintenance headache.
+
+## Scaling up: integrating multiple complex extensions
+
+The real power of this method becomes apparent when dealing with complex,
+interdependent extensions like PostGIS. PostGIS requires several companion
+extensions and shared library dependencies, which are notoriously difficult to
+manage manually.
+
+I can easily add PostGIS by simply listing it under `extensions`. Note the
+inclusion of the `ld_library_path` configuration for PostGIS; this is a vital
+element that ensures its dynamic linker paths are correctly configured for
+maximum reliability. Finally, I define all the necessary PostGIS-related
+companion extensions in the `Database` resource:
+
+```yaml
+{{< include "yaml/03.yaml" >}}
+```
+
+After applying this full manifest, I encourage you to check the validation
+commands from the previous section again. You'll find that the `/extensions/`
+directory now contains both `pgvector` and the PostGIS files, and the `\dx`
+output confirms that all **PostGIS** dependencies, including
+`postgis_topology`, have been successfully created in the database.
+
+## Summary
+
+The ability to mount extensions from separate images using `ImageVolume`
+with CloudNativePG 1.27+ is a game-changer. It allows us to:
+
+- **Decouple:** upgrade the core PostgreSQL image independently of the
+  extension images. This also applies to the build project (which is very
+  important for us maintainers and contributors of CloudNativePG).
+- **Dynamic and easy evaluation:** extensions can be added dynamically to an
+  existing cluster, making the evaluation of new features fast and
+  frictionless.
+- **Maintain small images:** my base `imageName` remains small, secure, and
+  simple.
+- **Ensure consistency:** CloudNativePG handles all the complex volume mounting
+  and dependency mapping, guaranteeing a consistent, immutable environment
+  across the entire cluster without needing custom Dockerfile builds.
+
+Finally, I want to mention that we are currently working to standardise the way
+we create these extension images in the [`postgres-extensions-containers` repository on GitHub](https://github.com/cloudnative-pg/postgres-extensions-containers).
+
+The goal of this project (see [issue #15](https://github.com/cloudnative-pg/postgres-extensions-containers/issues/15))
+is to scale up the number of supported extensions by providing a framework
+that can be used by more contributors to add extensions they like, as long as
+they become component owners/maintainers for that extension in the
+CloudNativePG community.
+I will cover our progress on this project in a future post.
+
+---
+
+Stay tuned for the upcoming recipes! For the latest updates, consider
+subscribing to my [LinkedIn](https://www.linkedin.com/in/gbartolini/) and
+[Twitter](https://twitter.com/_GBartolini_) channels.
+
+If you found this article informative, feel free to share it within your
+network on social media using the provided links below. Your support is
+immensely appreciated!
+
+<!--
+_Cover Picture: [“TITLE“](URL)._
+-->
+

content/posts/20251201-extensions/index.md

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+apiVersion: postgresql.cnpg.io/v1
+kind: Cluster
+metadata:
+  name: angus
+spec:
+  # the small, official `minimal` CNPG base image for Postgres 18
+  imageName: ghcr.io/cloudnative-pg/postgresql:18-minimal-trixie
+  instances: 1
+
+  storage:
+    size: 1Gi

content/posts/20251201-extensions/thumb.jpg

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+apiVersion: postgresql.cnpg.io/v1
+kind: Cluster
+metadata:
+  name: angus
+spec:
+  imageName: ghcr.io/cloudnative-pg/postgresql:18-minimal-trixie
+  instances: 1
+
+  storage:
+    size: 1Gi
+
+  postgresql:
+    extensions:
+    - name: pgvector
+      image:
+        reference: ghcr.io/cloudnative-pg/pgvector:0.8.1-18-trixie
+---
+apiVersion: postgresql.cnpg.io/v1
+kind: Database
+metadata:
+  name: angus-app
+spec:
+  name: app
+  owner: app
+  cluster:
+    name: angus
+  extensions:
+  - name: vector
+    version: '0.8.1'

content/posts/20251201-extensions/yaml/01.yaml

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+apiVersion: postgresql.cnpg.io/v1
+kind: Cluster
+metadata:
+  name: angus
+spec:
+  imageName: ghcr.io/cloudnative-pg/postgresql:18-minimal-trixie
+  instances: 1
+
+  storage:
+    size: 1Gi
+
+  postgresql:
+    extensions:
+    - name: pgvector
+      image:
+        reference: ghcr.io/cloudnative-pg/pgvector:0.8.1-18-trixie
+    - name: postgis
+      image:
+        reference: ghcr.io/cloudnative-pg/postgis-extension:3.6.1-18-trixie
+      ld_library_path:
+      - system
+---
+apiVersion: postgresql.cnpg.io/v1
+kind: Database
+metadata:
+  name: angus-app
+spec:
+  name: app
+  owner: app
+  cluster:
+    name: angus
+  extensions:
+  - name: vector
+    version: '0.8.1'
+  - name: postgis
+    version: '3.6.1'
+  - name: postgis_raster
+  - name: postgis_sfcgal
+  - name: fuzzystrmatch
+  - name: address_standardizer
+  - name: address_standardizer_data_us
+  - name: postgis_tiger_geocoder
+  - name: postgis_topology