Add new public function public.jsonb_diff_val

initdb/02_5_signalk_api_deps.sql

@@ -300,3 +300,27 @@ $$;
 COMMENT ON FUNCTION
     public.jsonb_recursive_merge
     IS 'Merging JSONB values';
+
+-- https://stackoverflow.com/questions/36041784/postgresql-compare-two-jsonb-objects
+CREATE OR REPLACE FUNCTION public.jsonb_diff_val(val1 JSONB,val2 JSONB)
+RETURNS JSONB AS $jsonb_diff_val$
+    DECLARE
+    result JSONB;
+    v RECORD;
+    BEGIN
+    result = val1;
+    FOR v IN SELECT * FROM jsonb_each(val2) LOOP
+        IF result @> jsonb_build_object(v.key,v.value)
+            THEN result = result - v.key;
+        ELSIF result ? v.key THEN CONTINUE;
+        ELSE
+            result = result || jsonb_build_object(v.key,'null');
+        END IF;
+    END LOOP;
+    RETURN result;
+    END;
+$jsonb_diff_val$ LANGUAGE plpgsql;
+-- Description
+COMMENT ON FUNCTION
+    public.jsonb_diff_val
+    IS 'Compare two jsonb objects';