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Signed-off-by: jayzhan211 <[email protected]>

datafusion/execution/src/memory_pool/pool.rs

@@ -58,8 +58,10 @@ impl MemoryPool for UnboundedMemoryPool {
 #[derive(Debug)]
 pub struct GreedyMemoryPool {
     pool_size: usize,
+    // Pool size limit for each consumer, if one of the consumer exceeds the limit, error is returned
     pool_size_per_consumer: HashMap<String, usize>,
     used: AtomicUsize,
+    // Memory usage for each consumer, used to check aginst `pool_size_per_consumer`
     used_per_consumer: RwLock<HashMap<String, AtomicUsize>>,
 }
 

datafusion/physical-plan/src/sorts/sort_preserving_merge.rs

@@ -409,13 +409,23 @@ mod tests {
     }
 
     #[tokio::test(flavor = "multi_thread")]
+    /// This test verifies that memory usage stays within limits when the tie breaker is enabled.
+    /// Any errors here could indicate unintended changes in tie breaker logic.
+    ///
+    /// Note: If you adjust constants in this test, ensure that memory usage differs
+    /// based on whether the tie breaker is enabled or disabled.
     async fn test_round_robin_tie_breaker_success() -> Result<()> {
         let task_ctx = generate_task_ctx_for_round_robin_tie_breaker()?;
         let spm = generate_spm_for_round_robin_tie_breaker(true)?;
         let _collected = collect(spm, task_ctx).await.unwrap();
         Ok(())
     }
 
+    /// This test verifies that memory usage stays within limits when the tie breaker is enabled.
+    /// Any errors here could indicate unintended changes in tie breaker logic.
+    ///
+    /// Note: If you adjust constants in this test, ensure that memory usage differs
+    /// based on whether the tie breaker is enabled or disabled.
     #[tokio::test(flavor = "multi_thread")]
     async fn test_round_robin_tie_breaker_fail() -> Result<()> {
         let task_ctx = generate_task_ctx_for_round_robin_tie_breaker()?;