From f8b625699282df07b4166809c0195760c7abb357 Mon Sep 17 00:00:00 2001
From: Eugene Kosov <claprix@yandex.ru>
Date: Sat, 15 Jul 2017 13:59:15 +0300
Subject: [PATCH] SQL: disallow ALTER CHANGE of system fields [fixes #213]

---
 mysql-test/suite/versioning/r/alter.result | 16 ++++++++++++++++
 mysql-test/suite/versioning/t/alter.test   | 18 ++++++++++++++++++
 sql/handler.cc                             |  6 ++++++
 sql/share/errmsg-utf8.txt                  |  3 +++
 4 files changed, 43 insertions(+)

diff --git a/mysql-test/suite/versioning/r/alter.result b/mysql-test/suite/versioning/r/alter.result
index 5dff4e706cb..a4e51b1a3e2 100644
--- a/mysql-test/suite/versioning/r/alter.result
+++ b/mysql-test/suite/versioning/r/alter.result
@@ -495,6 +495,22 @@ alter table t without system versioning, algorithm=inplace;
 select * from t;
 a	b
 2	NULL
+create or replace table t (
+a int,
+sys_trx_start bigint(20) unsigned generated always as row start,
+sys_trx_end bigint(20) unsigned generated always as row end,
+period for system_time(sys_trx_start, sys_trx_end)
+) with system versioning engine innodb;
+alter table t change column sys_trx_start asdf bigint unsigned;
+ERROR HY000: Can not change system versioning field 'sys_trx_start'
+create or replace table t (
+a int,
+sys_trx_start timestamp(6) generated always as row start,
+sys_trx_end timestamp(6) generated always as row end,
+period for system_time(sys_trx_start, sys_trx_end)
+) with system versioning engine myisam;
+alter table t change column sys_trx_start asdf timestamp(6);
+ERROR HY000: Can not change system versioning field 'sys_trx_start'
 call verify_vtq;
 No	A	B	C	D
 1	1	1	1	1
diff --git a/mysql-test/suite/versioning/t/alter.test b/mysql-test/suite/versioning/t/alter.test
index 40d65f258a3..edbb107b566 100644
--- a/mysql-test/suite/versioning/t/alter.test
+++ b/mysql-test/suite/versioning/t/alter.test
@@ -220,6 +220,24 @@ select * from t for system_time all;
 alter table t without system versioning, algorithm=inplace;
 select * from t;
 
+create or replace table t (
+  a int,
+  sys_trx_start bigint(20) unsigned generated always as row start,
+  sys_trx_end bigint(20) unsigned generated always as row end,
+  period for system_time(sys_trx_start, sys_trx_end)
+) with system versioning engine innodb;
+--error ER_VERS_ALTER_SYSTEM_FIELD
+alter table t change column sys_trx_start asdf bigint unsigned;
+
+create or replace table t (
+  a int,
+  sys_trx_start timestamp(6) generated always as row start,
+  sys_trx_end timestamp(6) generated always as row end,
+  period for system_time(sys_trx_start, sys_trx_end)
+) with system versioning engine myisam;
+--error ER_VERS_ALTER_SYSTEM_FIELD
+alter table t change column sys_trx_start asdf timestamp(6);
+
 call verify_vtq;
 drop table t;
 
diff --git a/sql/handler.cc b/sql/handler.cc
index ae685482219..9f4ab646aaa 100644
--- a/sql/handler.cc
+++ b/sql/handler.cc
@@ -6869,6 +6869,12 @@ bool Vers_parse_info::check_and_fix_alter(THD *thd, Alter_info *alter_info,
       {
         if (f->versioning == Column_definition::WITHOUT_VERSIONING)
           f->flags|= VERS_OPTIMIZED_UPDATE_FLAG;
+
+        if (f->change && (!strcmp(f->change, start) || !strcmp(f->change, end)))
+        {
+          my_error(ER_VERS_ALTER_SYSTEM_FIELD, MYF(0), f->change);
+          return true;
+        }
       }
     }
 
diff --git a/sql/share/errmsg-utf8.txt b/sql/share/errmsg-utf8.txt
index bbe4e6cff0e..1a386c4f16c 100644
--- a/sql/share/errmsg-utf8.txt
+++ b/sql/share/errmsg-utf8.txt
@@ -7591,3 +7591,6 @@ ER_VERS_HISTORY_LOCK
 
 ER_WRONG_TABLESPACE_NAME 42000
   eng "Incorrect tablespace name `%-.192s`"
+
+ER_VERS_ALTER_SYSTEM_FIELD
+        eng "Can not change system versioning field '%s'"