Add comment to clarify

vega · Apr 29, 2018 · e40978e · e40978e
1 parent 2b50edf
commit e40978e
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/src/compile/data/formatparse.ts b/src/compile/data/formatparse.ts
@@ -81,6 +81,8 @@ export class ParseNode extends DataFlowNode {
           }
           parse[fieldDef.field] = 'number';
         } else if (accessPathDepth(fieldDef.field) > 1) {
+          // For non-date/non-number (strings and booleans), derive a flattened field for a referenced nested field.
+          // (Parsing numbers / dates already flattens numeric and temporal fields.)
           parse[fieldDef.field] = 'flatten';
         }
       });