[GitHub] [doris] jacktengg commented on a diff in pull request #20564: [fix](case expr) fix coredump of case for null value

["jacktengg (via GitHub)" <gi...@apache.org>]

jacktengg commented on code in PR #20564:
URL: https://github.com/apache/doris/pull/20564#discussion_r1222940741


##########
be/src/vec/functions/function_case.h:
##########
@@ -332,13 +332,13 @@ class FunctionCase : public IFunction {
         bool then_null = false;
         for (int i = 1 + has_case; i < arguments.size() - has_else; i += 2) {
             auto then_column_ptr = block.get_by_position(arguments[i]).column;
-            if (then_column_ptr->is_nullable()) {
+            if (then_column_ptr->is_nullable() || then_column_ptr->only_null()) {
                 then_null = true;
             }
         }
         if constexpr (has_else) {
             auto else_column_ptr = block.get_by_position(arguments[arguments.size() - 1]).column;
-            if (else_column_ptr->is_nullable()) {
+            if (else_column_ptr->is_nullable() || else_column_ptr->only_null()) {

Review Comment:
   Change column_const's is_nullable will impact many existing code, e.g. casting column to ColumnNullable 
   
   ```
   template <PrimitiveType T>
   uint16_t BitmapFilterColumnPredicate<T>::evaluate(const vectorized::IColumn& column, uint16_t* sel,
                                                     uint16_t size) const {
       if (column.is_nullable()) {
           auto* nullable_col = reinterpret_cast<const vectorized::ColumnNullable*>(&column);
       }
   ```



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