MDEV-16024 transaction_registry.begin_timestamp is wrong for explicit transactions

Store transaction start time in thd->transaction.start_time.
THD::transaction_time() wraps over transaction.start_time taking into
account current status of BEGIN.

2 files changed, 17 insertions, 0 deletions

diff --git a/mysql-test/suite/versioning/t/trx_id.opt b/mysql-test/suite/versioning/t/trx_id.opt
new file mode 100644
index 00000000000..412290a7585
--- /dev/null
+++ b/mysql-test/suite/versioning/t/trx_id.opt
@@ -0,0 +1 @@
+--plugin-load-add=test_versioning
diff --git a/mysql-test/suite/versioning/t/trx_id.test b/mysql-test/suite/versioning/t/trx_id.test
index 0bf0e320835..4fb15f35366 100644
--- a/mysql-test/suite/versioning/t/trx_id.test
+++ b/mysql-test/suite/versioning/t/trx_id.test
@@ -153,5 +153,21 @@ delete from t1;
 select * from t1 for system_time as of timestamp'1990-1-1 00:00';
 select * from t1 for system_time as of NULL;
 
+--echo # MDEV-16024 transaction_registry.begin_timestamp is wrong for explicit transactions
+create or replace table t1 (
+    x int(11) default null,
+    row_start bigint(20) unsigned generated always as row start invisible,
+    row_end bigint(20) unsigned generated always as row end invisible,
+    period for system_time (row_start, row_end)
+) engine=innodb with system versioning;
+begin;
+set @ts1= now(6);
+--sleep 0.01
+insert into t1 values (1);
+commit;
+
+select row_start from t1 into @trx_id;
+select trt_begin_ts(@trx_id) <= @ts1 as BEGIN_TS_GOOD;
+
 drop database test;
 create database test;