MDEV-7150 Wrong auto increment values on INSERT .. ON DUPLICATE KEY UPDATE when the inserted columns include NULL in an auto-increment column

when restoring auto-inc value in INSERT ... ON DUPLICATE KEY UPDATE, take into account that
1. it may be changed in the UPDATE clause (old code did that)
2. it may be changed in the INSERT clause and then cause a dup key (old code missed that)

3 files changed, 18 insertions, 1 deletions

diff --git a/mysql-test/r/insert_update_autoinc-7150.result b/mysql-test/r/insert_update_autoinc-7150.result
new file mode 100644
index 00000000000..96773479310
--- /dev/null
+++ b/mysql-test/r/insert_update_autoinc-7150.result
@@ -0,0 +1,9 @@
+create table t1 (a int(10) auto_increment primary key, b int(11));
+insert t1 values (null,1);
+insert t1 values (null,2), (1,-1), (null,3) on duplicate key update b=values(b);
+select * from t1;
+a	b
+1	-1
+2	2
+3	3
+drop table t1;
diff --git a/mysql-test/t/insert_update_autoinc-7150.test b/mysql-test/t/insert_update_autoinc-7150.test
new file mode 100644
index 00000000000..1229898b4aa
--- /dev/null
+++ b/mysql-test/t/insert_update_autoinc-7150.test
@@ -0,0 +1,8 @@
+#
+# MDEV-7150 Wrong auto increment values on INSERT .. ON DUPLICATE KEY UPDATE when the inserted columns include NULL in an auto-increment column
+#
+create table t1 (a int(10) auto_increment primary key, b int(11));
+insert t1 values (null,1);
+insert t1 values (null,2), (1,-1), (null,3) on duplicate key update b=values(b);
+select * from t1;
+drop table t1;
diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
index ccfdf352f53..4500c4492c4 100644
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -1754,7 +1754,7 @@ int write_record(THD *thd, TABLE *table,COPY_INFO *info)
 
           table->file->adjust_next_insert_id_after_explicit_value(table->next_number_field->val_int());
         }
-        else
+        else if (prev_insert_id_for_cur_row)
         {
           table->file->restore_auto_increment(prev_insert_id_for_cur_row);
         }