Global postgres parameters for all instances

• Which image of the operator are you using? registry.opensource.zalan.do/acid/postgres-operator:v1.6.0
• Where do you run it - cloud or metal? Kubernetes or OpenShift? Bare Metal K8s
• Are you running Postgres Operator in production? yes
• Type of issue? question, feature request

Is it possible to add global parameters for all Postgres instances? We have almost all instances with the same logging parameters.

apiVersion: "acid.zalan.do/v1"
kind: postgresql
metadata:
  name: db-name
  namespace: default
spec:
  ...
  postgresql:
    version: "13"
    parameters:
      logging_collector: "off"
      log_connections: "on"
      log_disconnections: "on"
      log_duration: "on"
      log_min_duration_statement: "1000"
  ...

You have to transfer these parameters from one instance to another. It would be nice to describe them at the operator configuration level, rather than at the instance configuration level.

apiVersion: "acid.zalan.do/v1"
kind: OperatorConfiguration
metadata:
  name: postgresql-operator-configuration
configuration:
  ...
  parameters:
    logging_collector: "off"
    log_connections: "on"
    log_disconnections: "on"
    log_duration: "on"
    log_min_duration_statement: "1000"
  ...

Priority is given to the instance configuration, and to override the operator's configuration if the parameters match.

Start by tracing how OperatorConfiguration and the postgresql spec's parameters are read and applied to instances. Define the merge behavior so instance parameters override global values, then verify that shared logging parameters reach all instances while per-instance values take precedence.