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, 5 insertions, 0 deletions

diff --git a/mysql-test/suite/binlog/t/binlog_stm_cache_stat.test b/mysql-test/suite/binlog/t/binlog_stm_cache_stat.test
new file mode 100644
index 00000000000..0f5aa9f6013
--- /dev/null
+++ b/mysql-test/suite/binlog/t/binlog_stm_cache_stat.test
@@ -0,0 +1,5 @@
+# This is a wrapper for binlog.test so that the same test case can be used 
+# For both statement and row based bin logs 9/19/2005 [jbm]
+
+-- source include/have_binlog_format_statement.inc
+-- source extra/binlog_tests/binlog_cache_stat.test