MDEV-37312 ASAN errors or assertion failure upon attempt to UPDATE FOR PORTION violating long unique under READ COMMITTED

in case of a long unique conflict ha_write_row() used delete_row()
to remove the newly inserted row, and it used rnd_pos() to position
the cursor before deletion. This rnd_pos() was freeing and reallocating
blobs in record[0]. So when the code for FOR PORTION OF did
  store_record(record[2]);
  ha_write_row()
  restore_record(record[2]);
it ended up with blob pointers to a freed memory.

Let's use lookup_handler for deletion.

mysql-test/suite/period/r/long_unique.result

@@ -15,3 +15,20 @@ INSERT INTO t1 VALUES (1,'foo','2022-01-01', '2025-01-01');
 DELETE FROM t1 FOR PORTION OF app FROM '2023-01-01' TO '2024-01-01';
 ERROR 23000: Duplicate entry 'foo' for key 'b'
 DROP TABLE t1;
+# End of 10.5 tests
+#
+# MDEV-37312 ASAN errors or assertion failure upon attempt to UPDATE FOR PORTION violating long unique under READ COMMITTED
+#
+create table t1 (a int, f text unique, s datetime, e datetime, period for p(s,e)) engine=innodb;
+insert into t1 values (1,'foo','1900-01-01','2000-01-01'),(2,'bar','1900-01-01','2000-01-01');
+set transaction isolation level read committed;
+update t1 for portion of p from '1980-01-01' to '1980-01-02' set a = 1;
+ERROR 23000: Duplicate entry 'foo' for key 'f'
+drop table t1;
+create table t1 (a int, f text unique, s datetime, e datetime, period for p(s,e)) engine=innodb partition by hash (a);
+insert into t1 values (1,'foo','1900-01-01','2000-01-01'),(2,'bar','1900-01-01','2000-01-01');
+set transaction isolation level read committed;
+update t1 for portion of p from '1980-01-01' to '1980-01-02' set a = 1;
+ERROR 23000: Duplicate entry 'foo' for key 'f'
+drop table t1;
+# End of 10.6 tests

mysql-test/suite/period/t/long_unique.test

@@ -1,3 +1,4 @@
+--source include/have_innodb.inc
 --source include/have_partition.inc
 
 --echo #
@@ -21,3 +22,23 @@ INSERT INTO t1 VALUES (1,'foo','2022-01-01', '2025-01-01');
 DELETE FROM t1 FOR PORTION OF app FROM '2023-01-01' TO '2024-01-01';
 DROP TABLE t1;
 
+--echo # End of 10.5 tests
+
+--echo #
+--echo # MDEV-37312 ASAN errors or assertion failure upon attempt to UPDATE FOR PORTION violating long unique under READ COMMITTED
+--echo #
+create table t1 (a int, f text unique, s datetime, e datetime, period for p(s,e)) engine=innodb;
+insert into t1 values (1,'foo','1900-01-01','2000-01-01'),(2,'bar','1900-01-01','2000-01-01');
+set transaction isolation level read committed;
+--error ER_DUP_ENTRY
+update t1 for portion of p from '1980-01-01' to '1980-01-02' set a = 1;
+drop table t1;
+
+create table t1 (a int, f text unique, s datetime, e datetime, period for p(s,e)) engine=innodb partition by hash (a);
+insert into t1 values (1,'foo','1900-01-01','2000-01-01'),(2,'bar','1900-01-01','2000-01-01');
+set transaction isolation level read committed;
+--error ER_DUP_ENTRY
+update t1 for portion of p from '1980-01-01' to '1980-01-02' set a = 1;
+drop table t1;
+
+--echo # End of 10.6 tests

sql/handler.cc

@@ -3367,7 +3367,7 @@ int handler::create_lookup_handler()
   if (!(tmp= clone(table->s->normalized_path.str, table->in_use->mem_root)))
     return 1;
   lookup_handler= tmp;
-  return lookup_handler->ha_external_lock(table->in_use, F_RDLCK);
+  return lookup_handler->ha_external_lock(table->in_use, F_WRLCK);
 }
 
 LEX_CSTRING *handler::engine_name()
@@ -7774,16 +7774,16 @@ int handler::ha_write_row(const uchar *buf)
     if (lookup_handler != this) // INSERT IGNORE or REPLACE or ODKU
     {
       int olderror= error;
-      if ((error= rnd_init(0)))
+      if ((error= lookup_handler->rnd_init(0)))
         goto err;
       position(buf);
-      if ((error= rnd_pos(lookup_buffer, ref)))
+      if ((error= lookup_handler->rnd_pos(lookup_buffer, ref)))
         goto err;
 
       increment_statistics(&SSV::ha_delete_count);
       TABLE_IO_WAIT(tracker, PSI_TABLE_DELETE_ROW, MAX_KEY, error,
-                    { error= delete_row(buf);})
-      rnd_end();
+                    { error= lookup_handler->delete_row(buf);})
+      lookup_handler->rnd_end();
       if (!error)
         error= olderror;
     }
@@ -7916,8 +7916,7 @@ int handler::ha_delete_row(const uchar *buf)
   /*
     Normally table->record[0] is used, but sometimes table->record[1] is used.
   */
-  DBUG_ASSERT(buf == table->record[0] ||
-              buf == table->record[1]);
+  DBUG_ASSERT(buf == table->record[0] || buf == table->record[1]);
 
   MYSQL_DELETE_ROW_START(table_share->db.str, table_share->table_name.str);
   mark_trx_read_write();