From d179dd6f74354938e3fee2f6fa26d5d1600864e5 Mon Sep 17 00:00:00 2001
From: Daniel Black <daniel@mariadb.org>
Date: Tue, 26 May 2026 13:49:14 +1000
Subject: [PATCH] MDEV-31209 Queries with window functions do not obey KILL /
 max_statement_time

Window functions run in a loop in
Frame_cursor::compute_values_for_current_row which can include a large
number of rows.

Adjust this function to check for the current thd being killed.
---
 mysql-test/main/set_statement_notembedded.result |  9 +++++++++
 mysql-test/main/set_statement_notembedded.test   | 10 ++++++++++
 sql/sql_window.cc                                |  4 +++-
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/mysql-test/main/set_statement_notembedded.result b/mysql-test/main/set_statement_notembedded.result
index 67d2d8bc505cc..8c8608e992358 100644
--- a/mysql-test/main/set_statement_notembedded.result
+++ b/mysql-test/main/set_statement_notembedded.result
@@ -15,3 +15,12 @@ Max_statement_time_exceeded	1
 SELECT @@MAX_STATEMENT_TIME;
 @@MAX_STATEMENT_TIME
 0.000000
+#
+# MDEV-31209 Queries with window functions do not obey KILL / max_statement_time
+#
+create table t (i int);
+insert into t values(1),(2),(3);
+set statement max_statement_time=0.03 for select max(sleep(0.1)) over( ) from t;
+ERROR 70100: Query execution was interrupted (max_statement_time exceeded)
+drop table t;
+# End of 10.11 tests
diff --git a/mysql-test/main/set_statement_notembedded.test b/mysql-test/main/set_statement_notembedded.test
index 95d3efd40cacd..e71a0f5ee5c53 100644
--- a/mysql-test/main/set_statement_notembedded.test
+++ b/mysql-test/main/set_statement_notembedded.test
@@ -11,4 +11,14 @@ SET STATEMENT MAX_STATEMENT_TIME=1 FOR SELECT SLEEP(10);
 SHOW STATUS LIKE "max_statement_time_exceeded";
 SELECT @@MAX_STATEMENT_TIME;
 
+--echo #
+--echo # MDEV-31209 Queries with window functions do not obey KILL / max_statement_time
+--echo #
 
+create table t (i int);
+insert into t values(1),(2),(3);
+--error ER_STATEMENT_TIMEOUT
+set statement max_statement_time=0.03 for select max(sleep(0.1)) over( ) from t;
+drop table t;
+
+--echo # End of 10.11 tests
diff --git a/sql/sql_window.cc b/sql/sql_window.cc
index 73db592fbc113..de4fb30258e58 100644
--- a/sql/sql_window.cc
+++ b/sql/sql_window.cc
@@ -2255,6 +2255,7 @@ class Frame_scan_cursor : public Frame_cursor
      between them, top bound row  and bottom bound row inclusive. */
   void compute_values_for_current_row()
   {
+    THD *thd= current_thd;
     if (top_bound.is_outside_computation_bounds() ||
         bottom_bound.is_outside_computation_bounds())
       return;
@@ -2265,7 +2266,8 @@ class Frame_scan_cursor : public Frame_cursor
 
     cursor.move_to(start_rownum);
 
-    for (ha_rows idx= start_rownum; idx <= bottom_rownum; idx++)
+    for (ha_rows idx= start_rownum; idx <= bottom_rownum
+         && !thd->check_killed(true); idx++)
     {
       if (cursor.fetch()) //EOF
         break;