From d3ec65f1b1106c113e2baf48d467f580323f5ff9 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 17 Dec 2025 14:33:52 +0000
Subject: [PATCH 1/2] Initial plan


From 06cdb5783a8f16da86937ed1523db0774157e874 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 17 Dec 2025 14:41:37 +0000
Subject: [PATCH 2/2] Document thread-safety of Arrays.parallelSort usage

Co-authored-by: zaleslaw <1198621+zaleslaw@users.noreply.github.com>
---
 .../kotlinx/dataframe/jupyter/KotlinNotebookPluginUtils.kt    | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/KotlinNotebookPluginUtils.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/KotlinNotebookPluginUtils.kt
index 9781af2c90..a5697f6695 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/KotlinNotebookPluginUtils.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/jupyter/KotlinNotebookPluginUtils.kt
@@ -133,6 +133,10 @@ public object KotlinNotebookPluginUtils {
             val finalComparator = if (isDesc[0]) comparator.reversed() else comparator
 
             val permutation = Array(column.size()) { it }
+            // parallelSort is thread-safe here: the comparator only performs concurrent reads from the column,
+            // and column.get() is a simple, side-effect-free access to an underlying List.
+            // Standard List implementations (ArrayList, etc.) are safe for concurrent reads
+            // as long as there are no concurrent modifications to the dataframe.
             Arrays.parallelSort(permutation, finalComparator)
             return SortedDataFrameView(df, permutation.asList())
         }