qc_mysqlembedded does not look into functions when collecting
the affected fields of a query. Therefore the affected fields
of a query like
SELECT concat(a, "", "") from X where b = 1;
will be "b" and not "a b" as it should be.
qc_mysqlembedded used Item::next for traversing the fields of WHERE.
That is not correct as next is not intended for that purpose:
/**
Intrusive list pointer for free list. If not null, points to the next
Item on some Query_arena's free list. For instance, stored procedures
have their own Query_arena's.
@see Query_arena::free_list
*/
Item *next;
In pratice this meant that the fields in the SELECT part were reported
twice and that, depending on the query, all fields of WHERE were *not*
reported. For instance, the result for
SELECT a from X WHERE b = 1 and c = 2;
would correctly be "a b c" (in fact, it would be "a b c a"), but
the result for
SELECT a from X WHERE b = 1 and c = 2 and d = 3;
would also be "a b c".
The event distribution error messages were not truly errors but only rare
corner cases that usually don't happen. This doesn't mean that they should
be treated as errors and treating them as warnings is more helpful.
When a slave transitions from catchup mode to up-to-date mode, it is possible
that events are being distributed and the slave appears to be lagging behind.
The added comment explain why it happens and how it is handled to make the code
clearer.
Client authentication problems are easier to solve when the client IP is logged
in case a failed authentication attempt is made. This will also make it easier
to detect possible security problems.
The log manager wasn't initialized implicitly when a log message was written.
This caused all logged messages to be ignored before the log manager was
initialized.
When a slave transitions from catchup mode to up-to-date mode, an error
message is logged because the slave is at an unexpected position. This
error message should not be logged because it is a possible and an expected
situation.
The check for rotate event conditions was wrong which led to false error
message about unexpected binlog file and position combinations.
The position of the last event was reset every time a file was opened which
caused problems when the binlog file was rotated. The slave's current positions
were compared to the position where the last event started and because the
last_event_pos variable didn't point to the rotate event of the previous binlog,
the slave's never got the rotate event.
The name of the binlog file was added to the log message where a slave
is behind the master but the same file is used. This makes debugging the problem
a bit easier.
The decision to send an event to a slave can now only be made in one place.
This will force all events to pass the same checks before they are sent to
the slaves.
The position of the next event to be written was used as the position
of the current event. This caused the checks for the position of the current
safe event to fail and the non-transaction safe version was used.
This only happened with events that are not done inside a transaction i.e.
DDL statements.
The message is logged when a DDL statement is executed. It should not be
logged if trx_safe is on since the current_safe_event should always point
at the event we are sending. The current_safe_event is set to the wrong value
which causes this message to be logged.
Due to the false positives caused by this, the message is removed.
The message now states the location where it was called from and the amount
of events received from the master. In addition to this, new logging was
added when unsafe events are sent to slaves when transaction safety is enabled.
The duplicate event error message now logs the length of the slave's
write queue. This will tell how much data is still buffered inside MaxScale
when duplicate events are detected.
If a duplicate event is detected the state of the slave is set
to BLRS_ERRORED and the connection is closed. That way the
duplicate event will not break the slave, and it will pick
up its state when it reconnects.
When an event is sent to a slave, we store information about the
event and who sent it, so that we can detect if the same event is
sent twice. If a duplicate event is detected, we log information
about it.
The service permission checks did not check for SELECT privileges on
mysql.tables_priv which caused confusing error messages. The database
grant erros also did not log the MySQL error message which is often very
helpful when resolving permission errors.
The readwritesplit assumed that the execution of a session command would
always succeed. This is not the case when a write to the backend server
fails and it is not something that shouldn't happen.
