remove 'vers_auto_decrement'

Do not generate fake values when adding an auto-inc column to a versioned
table. This is not a auto-inc issue, but a more general case of adding
a not nullalble unique column to a table with history. We don't support
it yet, not even with a special auto-inc hack. As a workaround, one
can use a nullable unique column, that works.

mysql-test/suite/versioning/r/alter.result

@@ -426,17 +426,24 @@ No	A	B	C	D
 create or replace table t (a int) with system versioning;
 insert into t values (1), (2), (3);
 delete from t where a<3;
+alter table t add b int not null unique;
+ERROR 23000: Duplicate entry '...' for key 'b'
 alter table t add b int auto_increment unique;
+ERROR 42000: Table '#sql-temporary' uses an extension that doesn't exist in this MariaDB version
+alter table t add b int auto_increment null unique;
+select * from t;
+a	b
+3	1
 select * from t for system_time all;
 a	b
-1	-1
-2	-2
+1	NULL
+2	NULL
 3	1
-insert into t values (4, NULL);
+insert into t values (4, 0);
 select * from t for system_time all;
 a	b
-1	-1
-2	-2
+1	NULL
+2	NULL
 3	1
 4	2
 create or replace table t (a int) with system versioning engine=innodb;
@@ -467,17 +474,17 @@ No	A	B	C	D
 create or replace table t (a int) with system versioning;
 insert into t values (1), (2), (3);
 delete from t where a<3;
-alter table t add b tinyint auto_increment unique;
+alter table t add b tinyint auto_increment null unique;
 select * from t for system_time all;
 a	b
-1	-1
-2	-2
+1	NULL
+2	NULL
 3	1
-insert into t values (4, NULL);
+insert into t values (4, 0);
 select * from t for system_time all;
 a	b
-1	-1
-2	-2
+1	NULL
+2	NULL
 3	1
 4	2
 create or replace table t (

mysql-test/suite/versioning/t/alter.test

@@ -219,9 +219,16 @@ call verify_vtq;
 create or replace table t (a int) with system versioning;
 insert into t values (1), (2), (3);
 delete from t where a<3;
+--replace_regex /'0-[- 0-9.:]+'/'...'/
+--error ER_DUP_ENTRY
+alter table t add b int not null unique;
+--replace_regex /#sql-[0-9a-f_]*/#sql-temporary/
+--error ER_UNSUPPORTED_EXTENSION
 alter table t add b int auto_increment unique;
+alter table t add b int auto_increment null unique;
+select * from t;
 select * from t for system_time all;
-insert into t values (4, NULL);
+insert into t values (4, 0);
 select * from t for system_time all;
 
 create or replace table t (a int) with system versioning engine=innodb;
@@ -240,9 +247,9 @@ insert into t values (1), (2), (3);
 delete from t where a<3;
 # kvm-deb-trusty-ppc64le fails with "Out of range value for column 'b' at row 3"
 --error 0,ER_WARN_DATA_OUT_OF_RANGE
-alter table t add b tinyint auto_increment unique;
+alter table t add b tinyint auto_increment null unique;
 select * from t for system_time all;
-insert into t values (4, NULL);
+insert into t values (4, 0);
 select * from t for system_time all;
 
 create or replace table t (

sql/handler.cc

@@ -3056,35 +3056,24 @@ int handler::update_auto_increment()
   enum enum_check_fields save_count_cuted_fields;
   DBUG_ENTER("handler::update_auto_increment");
 
-  // System Versioning: handle ALTER ADD COLUMN AUTO_INCREMENT
-  if (thd->lex->sql_command == SQLCOM_ALTER_TABLE && table->versioned())
+  // ALTER TABLE ... ADD COLUMN ... AUTO_INCREMENT
+  if (thd->lex->sql_command == SQLCOM_ALTER_TABLE)
+  {
+    if (table->versioned())
     {
       Field *end= table->vers_end_field();
       DBUG_ASSERT(end);
       bitmap_set_bit(table->read_set, end->field_index);
       if (!end->is_max())
       {
-      uchar *ptr= table->next_number_field->ptr;
-      switch (table->next_number_field->pack_length())
-      {
-      case 8:
-        int8store(ptr, vers_auto_decrement--);
-        break;
-      case 4:
-        int4store(ptr, vers_auto_decrement--);
-        break;
-      case 2:
-        int2store(ptr, vers_auto_decrement--);
-        break;
-      case 1:
-        *ptr= static_cast<uchar>(vers_auto_decrement--);
-        break;
-      default:
-        DBUG_ASSERT(false);
-      }
+        if (!table->next_number_field->real_maybe_null())
+          DBUG_RETURN(HA_ERR_UNSUPPORTED);
+        table->next_number_field->set_null();
         DBUG_RETURN(0);
       }
     }
+    table->next_number_field->set_notnull();
+  }
 
   /*
     next_insert_id is a "cursor" into the reserved interval, it may go greater

sql/handler.h

@@ -2865,8 +2865,6 @@ class handler :public Sql_alloc
   */
   uint auto_inc_intervals_count;
 
-  ulonglong vers_auto_decrement;
-
   /**
     Instrumented table associated with this handler.
     This member should be set to NULL when no instrumentation is in place,

sql/sql_table.cc

@@ -10112,7 +10112,6 @@ copy_data_between_tables(THD *thd, TABLE *from, TABLE *to,
   }
   else if (keep_versioned)
   {
-    to->file->vers_auto_decrement= 0xffffffffffffffff;
     if (thd->variables.vers_alter_history == VERS_ALTER_HISTORY_SURVIVE)
     {
       query_start= thd->query_start_TIME();