[GitHub] [arrow] Dandandan commented on a change in pull request #9926: ARROW-12254: [Rust][DataFusion] Stop polling limit input once limit is reached

[GitBox <gi...@apache.org>]

Dandandan commented on a change in pull request #9926:
URL: https://github.com/apache/arrow/pull/9926#discussion_r608752879



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File path: rust/datafusion/src/physical_plan/limit.rs
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@@ -200,30 +200,39 @@ pub fn truncate_batch(batch: &RecordBatch, n: usize) -> RecordBatch {
 
 /// A Limit stream limits the stream to up to `limit` rows.
 struct LimitStream {
+    /// The maximum number of rows to produce
     limit: usize,
-    input: SendableRecordBatchStream,
-    // the current count
+    /// The input to read from. This is set to None once the limit is

Review comment:
       Is this necessary? It can be based on `self.current_len == self.limit` or otherwise a boolean flag like `limit_exhausted`?




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