[minor](column) remove function "remove_low_cardinality"

be/src/vec/columns/column.h

@@ -100,10 +100,6 @@ class IColumn : public COW<IColumn> {
   */
     virtual Ptr convert_column_if_overflow() { return get_ptr(); }
 
-    /// If column isn't ColumnLowCardinality, return itself.
-    /// If column is ColumnLowCardinality, transforms is to full column.
-    virtual Ptr convert_to_full_column_if_low_cardinality() const { return get_ptr(); }
-
     /// If column isn't ColumnDictionary, return itself.
     /// If column is ColumnDictionary, transforms is to predicate column.
     virtual MutablePtr convert_to_predicate_column_if_dictionary() { return get_ptr(); }

be/src/vec/columns/column_const.cpp

@@ -72,10 +72,6 @@ ColumnPtr ColumnConst::convert_to_full_column() const {
     return data->replicate(Offsets(1, cast_set<Offset>(s)));
 }
 
-ColumnPtr ColumnConst::remove_low_cardinality() const {
-    return ColumnConst::create(data->convert_to_full_column_if_low_cardinality(), s);
-}
-
 ColumnPtr ColumnConst::filter(const Filter& filt, ssize_t /*result_size_hint*/) const {
     column_match_filter_size(s, filt.size());
 

be/src/vec/columns/column_const.h

@@ -118,8 +118,6 @@ class ColumnConst final : public COWHelper<IColumn, ColumnConst> {
 
     bool is_variable_length() const override { return data->is_variable_length(); }
 
-    ColumnPtr remove_low_cardinality() const;
-
     std::string get_name() const override { return "Const(" + data->get_name() + ")"; }
 
     void resize(size_t new_size) override { s = new_size; }

be/src/vec/functions/function.cpp

@@ -285,14 +285,6 @@ DataTypePtr FunctionBuilderImpl::get_return_type_without_low_cardinality(
 DataTypePtr FunctionBuilderImpl::get_return_type(const ColumnsWithTypeAndName& arguments) const {
     if (use_default_implementation_for_low_cardinality_columns()) {
         ColumnsWithTypeAndName args_without_low_cardinality(arguments);
-
-        for (ColumnWithTypeAndName& arg : args_without_low_cardinality) {
-            bool is_const = arg.column && is_column_const(*arg.column);
-            if (is_const) {
-                arg.column = assert_cast<const ColumnConst&>(*arg.column).remove_low_cardinality();
-            }
-        }
-
         auto type_without_low_cardinality =
                 get_return_type_without_low_cardinality(args_without_low_cardinality);
 

be/src/vec/functions/nullif.cpp

@@ -67,14 +67,6 @@ class FunctionNullIf : public IFunction {
 
     static DataTypePtr get_return_type_for_equal(const ColumnsWithTypeAndName& arguments) {
         ColumnsWithTypeAndName args_without_low_cardinality(arguments);
-
-        for (ColumnWithTypeAndName& arg : args_without_low_cardinality) {
-            bool is_const = arg.column && is_column_const(*arg.column);
-            if (is_const) {
-                arg.column = assert_cast<const ColumnConst&>(*arg.column).remove_low_cardinality();
-            }
-        }
-
         if (!arguments.empty()) {
             if (have_null_column(arguments)) {
                 return make_nullable(std::make_shared<doris::vectorized::DataTypeUInt8>());