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samples/postgres/README.md

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+# Switching to the Official Postgres Image
+
+If you want to move from the Bitnami Postgres image to the official Postgres image, set:
+
+```
+components:
+  database: false
+  postgres: true
+global:
+  database:
+    url: "jdbc:postgresql://{{ .component.prefix }}postgres:5432/{{ .this.database.name }}"
+```
+
+in the values file. This will instantiate the official Postgres image.
+All values are identical.
+
+You can also run both components side-by-side to perform migrations.
+
+Make sure you set the database URL to the new DB when you are done.
+
+# Migration Scenario
+
+1. Add the postgres component
+
+```
+components:
+  database: true
+  postgres: true
+```
+
+2. Copy the database from the `database` component to the `postgres` component (single DB)
+
+Because default-deny egress is enabled for the instance, allow temporary egress for the migration client:
+
+```
+kubectl apply -n lab -f - <<'EOF1'
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: sample-postgres-allow-migration-egress
+spec:
+  podSelector:
+    matchLabels:
+      nplus/group: sample-postgres
+      nplus/type: core
+  policyTypes:
+  - Egress
+  egress:
+  - to:
+    - podSelector:
+        matchLabels:
+          nplus/group: sample-postgres
+          nplus/type: database
+  - to:
+    - podSelector:
+        matchLabels:
+          nplus/group: sample-postgres
+          nplus/type: postgres
+EOF1
+```
+
+```
+kubectl run -n lab pg-client --rm -i --image=postgres:17 \
+  --labels nplus/group=sample-postgres,nplus/type=core -- \
+  sh -c 'export PGPASSWORD=nscale; \
+         pg_dump -h sample-postgres-database -U nscale -Fc nscale | \
+         pg_restore -h sample-postgres-postgres -U nscale -d nscale --clean --if-exists'
+```
+
+Clean up the temporary egress rule:
+
+```
+kubectl delete -n lab networkpolicy sample-postgres-allow-migration-egress
+```
+
+3. Set nappl to use the new postgres component
+
+```
+global:
+  database:
+    url: "jdbc:postgresql://{{ .component.prefix }}postgres:5432/{{ .this.database.name }}"
+```
+
+4. Remove the old database component
+
+```
+components:
+  database: false
+  postgres: true
+```