[GitHub] [arrow-datafusion] Ted-Jiang commented on a diff in pull request #2694: combine limit and offset

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

Ted-Jiang commented on code in PR #2694:
URL: https://github.com/apache/arrow-datafusion/pull/2694#discussion_r889657737


##########
datafusion/core/src/physical_plan/limit.rs:
##########
@@ -176,17 +184,18 @@ impl ExecutionPlan for GlobalLimitExec {
 
     fn statistics(&self) -> Statistics {
         let input_stats = self.input.statistics();
+        let skip = self.skip.unwrap_or(0);
         match input_stats {
             // if the input does not reach the limit globally, return input stats
             Statistics {
                 num_rows: Some(nr), ..
-            } if nr <= self.limit => input_stats,
+            } if nr - skip <= self.fetch.unwrap_or(usize::MAX) => input_stats,

Review Comment:
   nit: like
   ```
   if the input is greater than the limit, the num_row will be the limit
   ```
   and 
   ```
   // if the input is greater than the limit, the num_row will be greater
   // than the limit because the partitions will be limited separatly
   // the statistic
   ```
   limit should change to fetch



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