Draft patch that fixes and a sketches test cases for:

Bug#20837 Apparent change of isolation level during transaction,
Bug#46527 COMMIT AND CHAIN RELEASE does not make sense,
Bug#53343 completion_type=1, COMMIT/ROLLBACK AND CHAIN don't 
preserve the isolation level
Bug#53346 completion_type has strange effect in a stored 
procedure/prepared statement

Make thd->tx_isolation mean strictly "current transaction 
isolation level"
Make thd->variables.tx_isolation mean "current session isolation
level".
The current transaction isolation level is now established
at transaction start. If there was a SET TRANSACTION
ISOLATION LEVEL statement, the value is taken from it.
Otherwise, the session value is used.
A change in a session value, made while a transaction is active,
whereas still allowed, no longer has any effect on the
current transaction isolation level. This is an incompatible
change.
A change in a session isolation level, made while there is
no active transaction, overrides SET TRANSACTION statement,
if there was any.
Changed the impelmentation to not look at @@session.completion_type
in the parser, and thus fixed Bug#53346.
Changed the parser to not allow AND NO CHAIN RELEASE,
and thus fixed Bug#46527.
Changed the transaction API to take the current transaction
isolation level into account:
- BEGIN/COMMIT now do preserve the current transaction
isolation level if chaining is on.
- implicit commit, XA COMMIT or XA ROLLBACK or autocommit don't.

1 files changed, 45 insertions, 0 deletions

diff --git a/mysql-test/r/parser.result b/mysql-test/r/parser.result
index 467bb7c5cb8..0cfde6dd2a0 100644
--- a/mysql-test/r/parser.result
+++ b/mysql-test/r/parser.result
@@ -618,3 +618,48 @@ DROP TABLE t1, t2, t3;
 #
 # End of 5.1 tests
 #
+# Bug#46527 "COMMIT AND CHAIN RELEASE does not make sense"
+#
+COMMIT AND CHAIN RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'RELEASE' at line 1
+COMMIT AND NO CHAIN RELEASE;
+COMMIT RELEASE;
+COMMIT CHAIN RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHAIN RELEASE' at line 1
+COMMIT NO CHAIN RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHAIN RELEASE' at line 1
+COMMIT AND NO RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'RELEASE' at line 1
+COMMIT AND RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'RELEASE' at line 1
+COMMIT NO RELEASE;
+COMMIT CHAIN NO RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHAIN NO RELEASE' at line 1
+COMMIT NO CHAIN NO RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHAIN NO RELEASE' at line 1
+COMMIT AND RELEASE CHAIN;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'RELEASE CHAIN' at line 1
+COMMIT AND NO CHAIN NO RELEASE;
+ROLLBACK AND CHAIN RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'RELEASE' at line 1
+ROLLBACK AND NO CHAIN RELEASE;
+ROLLBACK RELEASE;
+ROLLBACK CHAIN RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHAIN RELEASE' at line 1
+ROLLBACK NO CHAIN RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHAIN RELEASE' at line 1
+ROLLBACK AND NO RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'RELEASE' at line 1
+ROLLBACK AND RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'RELEASE' at line 1
+ROLLBACK NO RELEASE;
+ROLLBACK CHAIN NO RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHAIN NO RELEASE' at line 1
+ROLLBACK NO CHAIN NO RELEASE;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'CHAIN NO RELEASE' at line 1
+ROLLBACK AND RELEASE CHAIN;
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'RELEASE CHAIN' at line 1
+ROLLBACK AND NO CHAIN NO RELEASE;
+#
+# End of 5.5 tests
+#