MDEV-14823, MDEV-15956 Versioning error messages fixes

MDEV-14823 Wrong error message upon selecting from a system_time partition
MDEV-15956 Strange ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN upon ALTER on versioning column

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

@@ -524,5 +524,9 @@ ERROR HY000: System versioning tables in the `mysql` database are not suported
 alter table user add system versioning;
 ERROR HY000: System versioning tables in the `mysql` database are not suported
 use test;
+# MDEV-15956 Strange ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN upon ALTER on versioning column
+create or replace table t1 (i int, j int as (i), s timestamp(6) as row start, e timestamp(6) as row end, period for system_time(s,e)) with system versioning;
+alter table t1 modify s timestamp(6) as row start;
+ERROR HY000: Can not change system versioning field `s`
 drop database test;
 create database test;

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

@@ -479,6 +479,10 @@ insert into t1 values (1),(2),(3);
 update t1 set a = 4;
 delete from t1;
 delete from t1 where a is not null;
+# MDEV-14823 Wrong error message upon selecting from a system_time partition
+create or replace table t1 (i int) with system versioning partition by system_time limit 10 (partition p0 history, partition pn current);
+select * from t1 partition (p0) for system_time all;
+ERROR HY000: SYSTEM_TIME partitions in table `t1` does not support historical query
 # Test cleanup
 drop database test;
 create database test;

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

@@ -449,5 +449,10 @@ create or replace table t (x int) with system versioning;
 alter table user add system versioning;
 use test;
 
+--echo # MDEV-15956 Strange ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN upon ALTER on versioning column
+create or replace table t1 (i int, j int as (i), s timestamp(6) as row start, e timestamp(6) as row end, period for system_time(s,e)) with system versioning;
+--error ER_VERS_ALTER_SYSTEM_FIELD
+alter table t1 modify s timestamp(6) as row start;
+
 drop database test;
 create database test;

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

@@ -425,6 +425,11 @@ update t1 set a = 4;
 delete from t1;
 delete from t1 where a is not null;
 
+--echo # MDEV-14823 Wrong error message upon selecting from a system_time partition
+create or replace table t1 (i int) with system versioning partition by system_time limit 10 (partition p0 history, partition pn current);
+--error ER_VERS_QUERY_IN_PARTITION
+select * from t1 partition (p0) for system_time all;
+
 --echo # Test cleanup
 drop database test;
 create database test;

sql/handler.cc

@@ -7055,7 +7055,7 @@ bool Vers_parse_info::fix_alter_info(THD *thd, Alter_info *alter_info,
     {
       if (f->change.length && f->flags & VERS_SYSTEM_FIELD)
       {
-        my_error(ER_UNSUPPORTED_ACTION_ON_GENERATED_COLUMN, MYF(0));
+        my_error(ER_VERS_ALTER_SYSTEM_FIELD, MYF(0), f->field_name.str);
         return true;
       }
     }

sql/share/errmsg-utf8.txt

@@ -7915,3 +7915,5 @@ ER_UPDATED_COLUMN_ONLY_ONCE
         eng "The column %`s.%`s cannot be changed more than once in a single UPDATE statement"
 ER_EMPTY_ROW_IN_TVC
         eng "Row with no elements is not allowed in table value constructor in this context"
+ER_VERS_QUERY_IN_PARTITION
+        eng "SYSTEM_TIME partitions in table %`s does not support historical query"

sql/sql_select.cc

@@ -793,11 +793,7 @@ int SELECT_LEX::vers_setup_conds(THD *thd, TABLE_LIST *tables)
       {
         if (vers_conditions.is_set())
         {
-#define PART_VERS_ERR_MSG "%s PARTITION (%s)"
+          my_error(ER_VERS_QUERY_IN_PARTITION, MYF(0), table->alias.str);
-          char buf[NAME_LEN*2 + sizeof(PART_VERS_ERR_MSG)];
-          my_snprintf(buf, sizeof(buf), PART_VERS_ERR_MSG, table->alias.str,
-                      table->partition_names->head()->c_ptr());
-          my_error(ER_VERS_NOT_VERSIONED, MYF(0), buf);
           DBUG_RETURN(-1);
         }
         else