BUG#56343 binlog_cache_use status is bigger than expected

The binlog_cache_use is incremented twice when changes to a transactional table
are committed, i.e. TC_LOG_BINLOG::log_xid calls is called. The problem happens
because log_xid calls both binlog_flush_stmt_cache and binlog_flush_trx_cache
without checking if such caches are empty thus unintentionally increasing the
binlog_cache_use value twice.

To fix the problem we avoided incrementing the binlog_cache_use if the cache is
empty. We also decided to increment binlog_cache_use when the cache is truncated
as the cache is used although its content is discarded and is not written to the
binary log.

Note that binlog_cache_use is incremented for both types of cache, transactional
and non-transactional and that the behavior presented in this patch also applies
to the binlog_cache_disk_use.

Finally, we re-organized the code around the functions binlog_flush_trx_cache and
binlog_flush_stmt_cache.

mysql-test/extra/binlog_tests/binlog_cache_stat.test:
  Updated the test case with comments and additional tests to check both
  transactional and non-transactional changes and what happens when a 
  is transaction either committed or aborted.
mysql-test/suite/binlog/r/binlog_innodb.result:
  Updated the result file.
mysql-test/suite/binlog/r/binlog_mixed_cache_stat.result:
  Updated the result file.
mysql-test/suite/binlog/r/binlog_row_cache_stat.result:
  Updated the result file.
mysql-test/suite/binlog/r/binlog_stm_cache_stat.result:
  Updated the result file.
mysql-test/suite/binlog/t/binlog_mixed_cache_stat.test:
  Updated the test case with a new source file.
mysql-test/suite/binlog/t/binlog_row_cache_stat.test:
  Updated the test case with a new source file.
mysql-test/suite/binlog/t/binlog_stm_cache_stat.test:
  Updated the test case with a new source file.
sql/log_event.cc:
  Introduced debug information to check if Query_log_event("BEGIN"),
  Query_log_event("COMMIT") and Query_log_event("ROLLBACK").
sql/log_event.h:
  Guaranteed Xid_log_event is always classified as a transactional event.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/log_event.h b/sql/log_event.h
index 5d7250d8ebd..e2baffdb9b1 100644
--- a/sql/log_event.h
+++ b/sql/log_event.h
@@ -2504,7 +2504,7 @@ class Xid_log_event: public Log_event
    my_xid xid;
 
 #ifdef MYSQL_SERVER
-  Xid_log_event(THD* thd_arg, my_xid x): Log_event(thd_arg,0,0), xid(x) {}
+  Xid_log_event(THD* thd_arg, my_xid x): Log_event(thd_arg, 0, TRUE), xid(x) {}
 #ifdef HAVE_REPLICATION
   void pack_info(Protocol* protocol);
 #endif /* HAVE_REPLICATION */