containers:
      - name: airflow-postgresql
        image: "postgres:9.6.2"
        imagePullPolicy: ""
        args:
          - -c
          - 'max_connections=500'
          - -c
          - 'shared_preload_libraries=pg_stat_statements'

with src as (select 'a12345' as v)
select case when v ~ '^\d+$' then v::numeric else 0 end
  from src
;

WITH src(v) AS (
   VALUES ('a12345'), ('132213')
)
SELECT COALESCE((CASE WHEN v ~ '^[0123456789]+$' THEN v END)::numeric, 0)
  FROM src;