From c1492f3d077e47a015c6e4c5dcd2107b803ac3f4 Mon Sep 17 00:00:00 2001
From: Aleksey Midenkov <midenok@gmail.com>
Date: Sun, 30 Mar 2025 18:54:23 +0300
Subject: [PATCH] MDEV-36115 InnoDB: assertion: node->pcur->rel_pos ==
 BTR_PCUR_ON 	   in row_update_for_mysql

932ec586 (MDEV-23644) in TABLE::delete_row() added ha_delete_row() for
the case of HA_ERR_FOREIGN_DUPLICATE_KEY. The problem is
ha_update_row() called beforewards may change m_last_part which is
required for ha_delete_row() to delete from correct partition.

The fix reverts m_last_part in case ha_partition::update_row() fails.
---
 mysql-test/suite/versioning/r/partition.result | 14 ++++++++++++++
 mysql-test/suite/versioning/t/partition.test   | 16 ++++++++++++++++
 sql/ha_partition.cc                            |  3 ++-
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/mysql-test/suite/versioning/r/partition.result b/mysql-test/suite/versioning/r/partition.result
index 1ceb9c443a2..7e920fb3187 100644
--- a/mysql-test/suite/versioning/r/partition.result
+++ b/mysql-test/suite/versioning/r/partition.result
@@ -1791,6 +1791,20 @@ drop table t;
 create table t (a int) with system versioning partition by system_time partitions 3;
 ERROR HY000: Maybe missing parameters: no rotation condition for multiple HISTORY partitions.
 #
+# MDEV-36115 InnoDB: assertion: node->pcur->rel_pos == BTR_PCUR_ON
+#            in row_update_for_mysql
+#
+create table t (a int key) engine=innodb
+with system versioning
+partition by key() partitions 3;
+start transaction;
+insert into t values (1),(2),(3),(4),(5),(6),(7),(8);
+set timestamp=+1;
+delete from t;
+insert into t values (1),(2);
+DELETE from t;
+drop table t;
+#
 # End of 10.5 tests
 #
 set global innodb_stats_persistent= @save_persistent;
diff --git a/mysql-test/suite/versioning/t/partition.test b/mysql-test/suite/versioning/t/partition.test
index 840af2d6cec..3d31b1c6864 100644
--- a/mysql-test/suite/versioning/t/partition.test
+++ b/mysql-test/suite/versioning/t/partition.test
@@ -1563,6 +1563,22 @@ drop table t;
 --error WARN_VERS_PARAMETERS
 create table t (a int) with system versioning partition by system_time partitions 3;
 
+--echo #
+--echo # MDEV-36115 InnoDB: assertion: node->pcur->rel_pos == BTR_PCUR_ON
+--echo #            in row_update_for_mysql
+--echo #
+create table t (a int key) engine=innodb
+with system versioning
+partition by key() partitions 3;
+
+start transaction;
+insert into t values (1),(2),(3),(4),(5),(6),(7),(8);
+set timestamp=+1;
+delete from t;
+insert into t values (1),(2);
+DELETE from t;
+drop table t;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #
diff --git a/sql/ha_partition.cc b/sql/ha_partition.cc
index 64ffb25d4fe..d053eed62fe 100644
--- a/sql/ha_partition.cc
+++ b/sql/ha_partition.cc
@@ -4616,7 +4616,6 @@ int ha_partition::update_row(const uchar *old_data, const uchar *new_data)
   }
 
 
-  m_last_part= new_part_id;
   start_part_bulk_insert(thd, new_part_id);
   DBUG_ASSERT(!m_file[new_part_id]->row_logging);
   if (new_part_id == old_part_id)
@@ -4651,6 +4650,8 @@ int ha_partition::update_row(const uchar *old_data, const uchar *new_data)
       goto exit;
   }
 
+  m_last_part= new_part_id;
+
 exit:
   /*
     if updating an auto_increment column, update