MDEV-21921 Make transaction_isolation and transaction_read_only into system variables

In MariaDB, we have a confusing problem where:
* The transaction_isolation option can be set in a configuration file, but it cannot be set dynamically.
* The tx_isolation system variable can be set dynamically, but it cannot be set in a configuration file.

Therefore, we have two different names for the same thing in different contexts. This is needlessly confusing, and it complicates the documentation. The same thing applys for transaction_read_only.

MySQL 5.7 solved this problem by making them into system variables. https://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-20.html

This commit takes a similar approach by adding new system variables and marking the original ones as deprecated. This commit also resolves some legacy problems related to SET STATEMENT and transaction_isolation.

1 files changed, 2 insertions, 2 deletions

diff --git a/mysql-test/main/ps.test b/mysql-test/main/ps.test
index bb6ce7d4048..e779eefcb4d 100644
--- a/mysql-test/main/ps.test
+++ b/mysql-test/main/ps.test
@@ -763,13 +763,13 @@ prepare stmt from "select @@time_zone";
 execute stmt;
 set @@time_zone:='Japan';
 execute stmt;
-prepare stmt from "select @@tx_isolation";
+prepare stmt from "select @@transaction_isolation";
 execute stmt;
 set transaction isolation level read committed;
 execute stmt;
 set transaction isolation level serializable;
 execute stmt;
-set @@tx_isolation=default;
+set @@transaction_isolation=default;
 execute stmt;
 deallocate prepare stmt;