diff --git a/20230219044854_improve_functions.down.sql b/20230219044854_improve_functions.down.sql
new file mode 100644
index 0000000..333d701
--- /dev/null
+++ b/20230219044854_improve_functions.down.sql
@@ -0,0 +1,21 @@
+BEGIN;
+
+CREATE OR REPLACE FUNCTION is_sane_text(value TEXT)
+    RETURNS BOOLEAN
+    IMMUTABLE
+    PARALLEL SAFE
+    LANGUAGE plpgsql
+AS $$BEGIN
+    RETURN value IS NOT NULL AND value = btrim(value) AND length(value) > 0;
+END$$;
+
+CREATE OR REPLACE FUNCTION is_language_code(value VARCHAR)
+    RETURNS BOOLEAN
+    IMMUTABLE
+    PARALLEL SAFE
+    LANGUAGE plpgsql
+AS $$BEGIN
+    RETURN value IS NOT NULL AND value ~ '^[a-z]{2}$';
+END$$;
+
+COMMIT;
diff --git a/20230219044854_improve_functions.up.sql b/20230219044854_improve_functions.up.sql
new file mode 100644
index 0000000..8955745
--- /dev/null
+++ b/20230219044854_improve_functions.up.sql
@@ -0,0 +1,29 @@
+BEGIN;
+
+CREATE OR REPLACE FUNCTION is_sane_text(value TEXT)
+    RETURNS BOOLEAN
+    IMMUTABLE
+    PARALLEL SAFE
+    LANGUAGE plpgsql
+AS $$BEGIN
+    IF value IS NULL THEN
+        RETURN TRUE;
+    ELSE
+        RETURN value = btrim(value) AND length(value) > 0;
+    END IF;
+END$$;
+
+CREATE OR REPLACE FUNCTION is_language_code(value VARCHAR)
+    RETURNS BOOLEAN
+    IMMUTABLE
+    PARALLEL SAFE
+    LANGUAGE plpgsql
+AS $$BEGIN
+    IF value IS NULL THEN
+        RETURN TRUE;
+    ELSE
+        RETURN value ~ '^[a-z]{2}$';
+    END IF;
+END$$;
+
+COMMIT;