From b485e75bb2b36e615b09fcede860bc439fc57b4b Mon Sep 17 00:00:00 2001
From: "andres.suarez" <andres.suarez@supabase.io>
Date: Thu, 26 Mar 2026 17:49:12 +0100
Subject: [PATCH 1/2]  feat: add pg_class-based table size metrics to
 postgres_exporter

Deploy a custom queries.yml that exposes per-table row estimates and
sizes (table, index, toast) via pg_class.reltuples and pg_relation_size(),
as a cheap alternative to the disabled stat_user_tables collectors.
---
 ansible/files/queries.yml                    | 34 ++++++++++++++++++++
 ansible/tasks/internal/postgres-exporter.yml |  9 ++++++
 2 files changed, 43 insertions(+)
 create mode 100644 ansible/files/queries.yml

diff --git a/ansible/files/queries.yml b/ansible/files/queries.yml
new file mode 100644
index 0000000000..9e1bb88478
--- /dev/null
+++ b/ansible/files/queries.yml
@@ -0,0 +1,34 @@
+pg_table_size:
+  query: |
+    SELECT
+      n.nspname AS schema,
+      c.relname AS table,
+      c.reltuples AS row_estimate,
+      pg_total_relation_size(c.oid) AS total_bytes,
+      pg_relation_size(c.oid) AS table_bytes,
+      pg_indexes_size(c.oid) AS index_bytes,
+      pg_total_relation_size(c.reltoastrelid) AS toast_bytes
+    FROM pg_class c
+    JOIN pg_namespace n ON n.oid = c.relnamespace
+    WHERE c.relkind = 'r'
+      AND n.nspname NOT IN ('pg_catalog', 'information_schema')
+  metrics:
+    - schema:
+        usage: LABEL
+    - table:
+        usage: LABEL
+    - row_estimate:
+        usage: GAUGE
+        description: "Estimated row count from pg_class.reltuples"
+    - total_bytes:
+        usage: GAUGE
+        description: "Total size including indexes and toast"
+    - table_bytes:
+        usage: GAUGE
+        description: "Table data size"
+    - index_bytes:
+        usage: GAUGE
+        description: "Total index size"
+    - toast_bytes:
+        usage: GAUGE
+        description: "Toast size"
diff --git a/ansible/tasks/internal/postgres-exporter.yml b/ansible/tasks/internal/postgres-exporter.yml
index 0292157b2d..f4ec54d951 100644
--- a/ansible/tasks/internal/postgres-exporter.yml
+++ b/ansible/tasks/internal/postgres-exporter.yml
@@ -35,6 +35,15 @@
     extra_opts: [--strip-components=1]
   become: yes
 
+- name: deploy queries.yml for custom metrics
+  copy:
+    src: files/queries.yml
+    dest: /opt/postgres_exporter/queries.yml
+    owner: root
+    group: root
+    mode: '0644'
+  become: yes
+
 - name: exporter create a service
   template:
     src: files/postgres_exporter.service.j2

From 876c8c4f118fb37e5e060951f97435e85edf2290 Mon Sep 17 00:00:00 2001
From: "andres.suarez" <andres.suarez@supabase.io>
Date: Fri, 27 Mar 2026 09:05:53 +0100
Subject: [PATCH 2/2] feat: add pg_class-based table size metrics to
 postgres_exporter
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Deploys a custom `queries.yml` for postgres_exporter that exposes per-table
 row estimates and sizes via `pg_class`, as a cheap alternative to the disabled
 `stat_user_tables` collectors.

`--no-collector.stat_user_tables` and `--no-collector.statio_user_tables` are
  disabled because `pg_stat_user_tables` row counts are expensive on large DBs.
  `pg_class.reltuples` gives a good-enough estimate maintained by autovacuum —
  no sequential scan, negligible cost.

- `ansible/files/queries.yml` — new custom query exposing `pg_table_size`
metric family: `row_estimate`, `total_bytes`, `table_bytes`, `index_bytes`,
    `toast_bytes` (per schema/table)
  - `ansible/tasks/internal/postgres-exporter.yml` — Ansible task to deploy
    `queries.yml` to `/opt/postgres_exporter/queries.yml`

  The service already had `--extend.query-path="/opt/postgres_exporter/queries.yml"`
  in its ExecStart, so no service template change was needed.

Manually deployed to a staging DB and verified via the metrics endpoint.
All 5 metric families scraped correctly across `auth`, `storage`, and `vault`
schemas. Fixed a `NaN` edge case for `toast_bytes` on tables without a toast
table using `COALESCE(pg_total_relation_size(NULLIF(c.reltoastrelid, 0)), 0)`.

Note: `row_estimate = -1` is expected on empty/fresh tables — it means
autovacuum hasn't run yet. Will show real estimates on populated DBs.
---
 ansible/files/queries.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ansible/files/queries.yml b/ansible/files/queries.yml
index 9e1bb88478..a906819b50 100644
--- a/ansible/files/queries.yml
+++ b/ansible/files/queries.yml
@@ -7,7 +7,7 @@ pg_table_size:
       pg_total_relation_size(c.oid) AS total_bytes,
       pg_relation_size(c.oid) AS table_bytes,
       pg_indexes_size(c.oid) AS index_bytes,
-      pg_total_relation_size(c.reltoastrelid) AS toast_bytes
+      COALESCE(pg_total_relation_size(NULLIF(c.reltoastrelid, 0)), 0) AS toast_bytes
     FROM pg_class c
     JOIN pg_namespace n ON n.oid = c.relnamespace
     WHERE c.relkind = 'r'