backport from mysql-trunk

BUG #11754979 - 46675: ON DUPLICATE KEY UPDATE AND UPDATECOUNT() POSSIBLY WRONG 

The mysql_affected_rows() client call returns 3 instead of 2 on
INSERT ... ON DUPLICATE KEY UPDATE query with a duplicated key value.

The fix for the old bug #29692 was incomplete: unnecessary double
increment of "touched" rows still happened.

This bugfix removes:
1) unneeded increment of "touched" rows and
2) useless double resetting of auto-increment value.

sql/sql_insert.cc

@@ -1610,9 +1610,6 @@ int write_record(THD *thd, TABLE *table,COPY_INFO *info)
           goto before_trg_err;
 
         table->file->restore_auto_increment(prev_insert_id);
-        if (table->next_number_field)
-          table->file->adjust_next_insert_id_after_explicit_value(
-            table->next_number_field->val_int());
         info->touched++;
         if (!records_are_comparable(table) || compare_records(table))
         {
@@ -1649,8 +1646,6 @@ int write_record(THD *thd, TABLE *table,COPY_INFO *info)
         if (table->next_number_field)
           table->file->adjust_next_insert_id_after_explicit_value(
             table->next_number_field->val_int());
-        info->touched++;
-
         goto ok_or_after_trg_err;
       }
       else /* DUP_REPLACE */

tests/mysql_client_test.c

@@ -19660,6 +19660,34 @@ static void test_bug12337762()
   DBUG_VOID_RETURN;
 }
 
+
+/*
+  BUG 11754979 - 46675: ON DUPLICATE KEY UPDATE AND UPDATECOUNT() POSSIBLY WRONG
+*/
+
+static void test_bug11754979()
+{
+  MYSQL* conn;
+  DBUG_ENTER("test_bug11754979");
+
+  myheader("test_bug11754979");
+  DIE_UNLESS((conn= mysql_client_init(NULL)));
+  DIE_UNLESS(mysql_real_connect(conn, opt_host, opt_user,
+             opt_password, opt_db ? opt_db:"test", opt_port,
+             opt_unix_socket,  CLIENT_FOUND_ROWS));
+  myquery(mysql_query(conn, "DROP TABLE IF EXISTS t1"));
+  myquery(mysql_query(conn, "CREATE TABLE t1(id INT, label CHAR(1), PRIMARY KEY(id))"));
+  myquery(mysql_query(conn, "INSERT INTO t1(id, label) VALUES (1, 'a')"));
+  myquery(mysql_query(conn, "INSERT INTO t1(id, label) VALUES (1, 'a') "
+                            "ON DUPLICATE KEY UPDATE id = 4"));
+  DIE_UNLESS(mysql_affected_rows(conn) == 2);
+  myquery(mysql_query(conn, "DROP TABLE t1"));
+  mysql_close(conn);
+
+  DBUG_VOID_RETURN;
+}
+
+
 /*
   Read and parse arguments and MySQL options from my.cnf
 */
@@ -20005,6 +20033,7 @@ static struct my_tests_st my_tests[]= {
   { "test_bug56976", test_bug56976 },
   { "test_bug11766854", test_bug11766854 },
   { "test_bug12337762", test_bug12337762 },
+  { "test_bug11754979", test_bug11754979 },
   { 0, 0 }
 };