MDEV-17553 Enable setting start datetime for interval partitioned history of system versioned tables

* Explicit STARTS syntax
* SHOW CREATE
* Default STARTS rounding depending on INTERVAL type
* Warn when STARTS timestamp is later than query time
* Fix uninitialized Lex->create_last_non_select_table under
  mysql_unpack_partition()

Default STARTS rounding depending on INTERVAL type

If STARTS clause is omitted, default one is assigned with value
derived from query timestamp. The rounding is done on STARTS value
depending on INTERVAL type:

SECOND: no rounding is done;
MINUTE: timestamp seconds is set to 0;
HOUR: timestamp seconds and minutes are set to 0;
DAY, WEEK, MONTH and YEAR: timestamp seconds, minutes and hours are
set to 0 (the date of rotation is kept as current date).

1 files changed, 2 insertions, 8 deletions

diff --git a/mysql-test/suite/versioning/t/partition.test b/mysql-test/suite/versioning/t/partition.test
index e3acf53686e..7a4868e4785 100644
--- a/mysql-test/suite/versioning/t/partition.test
+++ b/mysql-test/suite/versioning/t/partition.test
@@ -2,6 +2,8 @@
 -- source suite/versioning/common.inc
 -- source suite/versioning/engines.inc
 
+call mtr.add_suppression("need more HISTORY partitions");
+
 set system_versioning_alter_history=keep;
 --echo # Check conventional partitioning on temporal tables
 
@@ -250,14 +252,6 @@ partition by system_time interval 0 second (
     partition pn current);
 
 --error ER_PARSE_ERROR
-create or replace table t1 (x int)
-with system versioning
-partition by system_time interval 1 second starts 12345 (
-    partition p0 history,
-    partition p1 history,
-    partition pn current);
-
---error ER_PARSE_ERROR
 create table t1 (i int) with system versioning
   partition by system_time interval 6 day limit 98
   (partition p0 history, partition ver_pn current);