chore: skip has_null check

src/mito2/src/read/dedup.rs

@@ -230,8 +230,10 @@ struct LastFieldsBuilder {
  /// Fields builders, lazy initialized.
  builders: Vec<Box<dyn MutableVector>>,
  /// Last fields to merge, lazy initialized.
+ /// Only initializes this field when `skip_merge()` is false.
  last_fields: Vec<Value>,
  /// Whether the last row (including `last_fields`) has null field.
+ /// Only sets this field when `has_delete` is false.
  has_null: bool,
  /// Whether the last row has delete op. If true, skips merging fields.
  has_delete: bool,
@@ -265,9 +267,12 @@ impl LastFieldsBuilder {
 
  let last_idx = batch.num_rows() - 1;
  let fields = batch.fields();
- self.has_null = fields.iter().any(|col| col.data.is_null(last_idx));
  // Safety: The last_idx is valid.
  self.has_delete = batch.op_types().get_data(last_idx).unwrap() == OpType::Delete as u8;
+ // If the row has been deleted, then we don't need to merge fields.
+ if !self.has_delete {
+ self.has_null = fields.iter().any(|col| col.data.is_null(last_idx));
+ }
 
  if self.skip_merge() {
  // No null field or the row has been deleted, no need to merge.