MDEV-16144 Default TIMESTAMP clause for SELECT from versioned

1. Removed TIMESTAMP/TRANSACTION unit auto-detection in favor of default TIMESTAMP.

Reasons:

1.1. rare practical use and doubtful advantage of such auto-detection;
1.2. it conflicts with MDEV-16226 (TRX_ID-based versioned tables performance improvement).

Needless check_unit membership removed.

2. SQL: versioning type handling refactoring

Vers_type_handler hierarchy stores versioning properties of type.

virtual Type_handler::vers() accesses specialization of
Vers_type_handler for specific type.

virtual Vers_type_handler::kind() returns versioning kind
(timestamp/trx_id).

Removed Type_handler::Vers_history_point_check_unit() in favor of
Type_handler::vers().

Renames:

require_timestamp() -> require_timestamp_error()
require_trx_id() -> require_trx_id_error()

EDIT by Alexander Barkov (@abarkov):

check_sys_fields() moved to Vers_type_handler::check_sys_fields()

1 files changed, 1 insertions, 4 deletions

diff --git a/mysql-test/suite/versioning/r/select.result b/mysql-test/suite/versioning/r/select.result
index f1ef954baa6..2cd9904b793 100644
--- a/mysql-test/suite/versioning/r/select.result
+++ b/mysql-test/suite/versioning/r/select.result
@@ -383,12 +383,9 @@ x
 select x from t1 for system_time as of transaction @trx_start;
 x
 1
-## no specifier (auto-detection)
+## no specifier (defaults to timestamp)
 select x from t1 for system_time as of @ts;
 x
-select x from t1 for system_time as of @trx_start;
-x
-1
 ### Issue #365, bug 4 (related to #226, optimized fields)
 create or replace table t1 (i int, b int) with system versioning;
 insert into t1 values (0, 0), (0, 0);