cant change logic once data are in that column

common/proto/table_validation.proto

@@ -52,6 +52,9 @@ message FieldValidation {
 
   // Field must be provided / treated as required by clients and server enforcement layers.
   bool required = 4;
+
+  // Once locked, this field's validation config cannot be changed.
+  bool locked = 15;
 }
 
 // Character length counting mode
@@ -191,6 +194,9 @@ service TableValidationService {
 
   // Snapshot a reusable set onto a concrete table field.
   rpc ApplyValidationSet(ApplyValidationSetRequest) returns (ApplyValidationSetResponse);
+
+  // Permanently lock one field's validation config.
+  rpc LockFieldValidation(LockFieldValidationRequest) returns (LockFieldValidationResponse);
 }
 
 message UpdateFieldValidationRequest {
@@ -320,3 +326,14 @@ message ApplyValidationSetResponse {
   string message = 2;
   FieldValidation validation = 3;
 }
+
+message LockFieldValidationRequest {
+  string profileName = 1;
+  string tableName = 2;
+  string dataKey = 3;
+}
+
+message LockFieldValidationResponse {
+  bool success = 1;
+  string message = 2;
+}