The problem was in a test case for Bug33507:
- when the number of active connections reaches the limit,
the server accepts only root connections. That's achieved by
accepting a connection, negotiating with the client and
checking user credentials. If it is not SUPER, the connection
is dropped.
- when the server accepts connection, it increases the counter;
- when the server drops connection, it decreases the counter;
- the race was in between of decreasing the counter and accepting
new connection:
- max_user_connections = 2;
- 2 oridinary user connections accepted;
- extra user connection is establishing;
- server checked user credentials, and sent 'Too many connections'
error;
- the client receives the error and establishes extra SUPER user
connection;
- the server however didn't decrease the counter (the extra
user connection still is "alive" in the server) -- so, the new
SUPER-user connection, will be dropped, because it exceeds
(max_user_connections + 1).
The fix is to implement "safe connect", which makes several attempts
to connect and use it in the test script.
The problem was that 'connect' command didn't set mysql_errno
variable, thus the script was unable to determine whether connection
was opened or not.
The fix is to set this variable.
Test cases will be added in the scope of Bug33507
into connect.test file.
The problem was that the COM_STMT_SEND_LONG_DATA was sending a response
packet if the prepared statement wasn't found in the server (due to
reconnection). The commands COM_STMT_SEND_LONG_DATA and COM_STMT_CLOSE
should not send any packets, even error packets should not be sent since
they are not expected by the client API.
The solution is to clear generated during the execution of the aforementioned
commands and to skip resend of prepared statement commands. Another fix is
that if the connection breaks during the send of prepared statement command,
the command is not sent again since the prepared statement is no longer in the
server.
Queries like:
SELECT ROW(1, 2) IN (SELECT t1.a, 2)
FROM t1 GROUP BY t1.a
or
SELECT ROW(1, 2) IN (SELECT t1.a, 2 FROM t2)
FROM t1 GROUP BY t1.a
lead to assertion failure in the
Item_in_subselect::row_value_transformer method in debugging
build, or to unexpected error message in release build:
ERROR 1247 (42S22): Reference '<list ref>' not supported (forward
reference in item list)
Unexpected error message and assertion failure have been
eliminated.
When there are no underlying tables specified for a merge table,
SHOW CREATE TABLE outputs a statement that cannot be executed. The
same is true for mysqldump (it generates dumps that cannot be
executed).
This happens because SQL parser does not accept empty UNION() clause.
This patch changes the following:
- it is now possible to execute CREATE/ALTER statement with
empty UNION() clause.
- the same as above, but still worth noting: it is now possible to
remove underlying tables mapping using ALTER TABLE ... UNION=().
- SHOW CREATE TABLE does not output UNION() clause if there are
no underlying tables specified for a merge table. This makes
mysqldump slightly smaller.
in some case.
ER_CON_COUNT_ERROR is defined with SQL state 08004. However, this SQL state is not always
returned.
This error can be thrown in two cases:
1. when an ordinary user (a user w/o SUPER privilege) is connecting,
and the number of active user connections is equal or greater than
max_connections.
2. when a user is connecting and the number of active user connections is
already (max_connections + 1) -- that means that no more connections will
be accepted regardless of the user credentials.
In the 1-st case, SQL state is correct.
The bug happens in the 2-nd case -- on UNIX the client gets 00000 SQL state, which is
absolutely wrong (00000 means "not error SQL state); on Windows
the client accidentally gets HY000 (which means "unknown SQL state).
The cause of the problem is that the server rejects extra connection
prior to read a packet with client capabilities. Thus, the server
does not know if the client supports SQL states or not (if the client
supports 4.1 protocol or not). So, the server supposes the worst and
does not send SQL state at all.
The difference in behavior on UNIX and Windows occurs because on Windows
CLI_MYSQL_REAL_CONNECT() invokes create_shared_memory(), which returns
an error (in default configuration, where shared memory is not configured).
Then, the client does not reset this error, so when the connection is
rejected, SQL state is HY000 (from the error from create_shared_memory()).
The bug appeared after test case for Bug#33507 -- before that, this behavior
just had not been tested.
The fix is to 1) reset the error after create_shared_memory();
2) set SQL state to 'unknown error' if it was not received from
the server.
A separate test case is not required, since the behavior is already
tested in connect.test.
Note for doc-team: the manual should be updated to say that under
some circumstances, 'Too many connections' has HY000 SQL state.
