required columns

common/proto/table_definition.proto

@@ -70,6 +70,10 @@ service TableDefinition {
   // indexes are created or dropped even when rows have already been stored.
   rpc SetTableIndexes(SetTableIndexesRequest) returns (SetTableIndexesResponse);
 
+  // Changes whether one existing column is required. Enabling the requirement
+  // is rejected while an active row has no value for the column.
+  rpc SetColumnRequired(SetColumnRequiredRequest) returns (SetColumnRequiredResponse);
+
   // Replaces the optional user-visible aliases for a fixed-option column.
   // Stored values remain stable machine values and scripts never depend on labels.
   rpc SetColumnOptionAliases(SetColumnOptionAliasesRequest) returns (SetColumnOptionAliasesResponse);
@@ -632,6 +636,24 @@ message SetTableIndexesResponse {
   int64 row_version = 3;
 }
 
+message SetColumnRequiredRequest {
+  string profile_name = 1;
+  string table_name = 2;
+  // Stable column identity returned in GetProfileDetails.column_behaviors.
+  int64 column_id = 3;
+  bool required = 4;
+  // Row version returned by GetProfileDetails when the column was read.
+  int64 expected_row_version = 5;
+}
+
+message SetColumnRequiredResponse {
+  bool success = 1;
+  int64 column_id = 2;
+  bool required = 3;
+  // New row version after the update, or the current version for a no-op.
+  int64 row_version = 4;
+}
+
 // One public option name. `value` identifies the option by its current public
 // alias and `alias` is its desired public alias; stored values remain internal.
 message OptionValueAlias {