Bug #16206: Superfluous COMMIT event in binlog when updating BDB in autocommit

	mode

This is a modification of serg's and guilhem's suggestion in the bug report,
in that it also causes the transaction log to be written to disc.


mysql-test/r/bdb.result:
  Add result.
mysql-test/t/bdb.test:
  Add test
sql/log.cc:
  Create a log-committing event that itself won't be written to the log when 
  we're in autocommit mode.
sql/log_event.cc:
  Add a new subclass of Query_log_event that doesn't write itself to the log, for
  cases where we only want to flush out the transaction and not also write about
  this event.
sql/log_event.h:
  Add a new subclass of Query_log_event that doesn't write itself to the log, for
  cases where we only want to flush out the transaction and not also write about
  this event.

3 files changed, 65 insertions, 5 deletions

diff --git a/sql/log.cc b/sql/log.cc
index ba02c9ba082..cfb90d398e6 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -36,6 +36,8 @@
 MYSQL_LOG mysql_log, mysql_slow_log, mysql_bin_log;
 ulong sync_binlog_counter= 0;
 
+static Muted_query_log_event invisible_commit;
+
 static bool test_if_number(const char *str,
 			   long *res, bool allow_wildcards);
 static bool binlog_init();
@@ -94,7 +96,9 @@ static int binlog_end_trans(THD *thd, IO_CACHE *trans_log, Log_event *end_ev)
 {
   int error=0;
   DBUG_ENTER("binlog_end_trans");
-  if (end_ev)
+
+  /* NULL denotes ROLLBACK with nothing to replicate */
+  if (end_ev != NULL)
     error= mysql_bin_log.write(thd, trans_log, end_ev);
 
   statistic_increment(binlog_cache_use, &LOCK_status);
@@ -126,14 +130,19 @@ static int binlog_commit(THD *thd, bool all)
   DBUG_ASSERT(mysql_bin_log.is_open() &&
      (all || !(thd->options & (OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN))));
 
-  if (!my_b_tell(trans_log))
+  if (my_b_tell(trans_log) == 0)
   {
     // we're here because trans_log was flushed in MYSQL_LOG::log()
     DBUG_RETURN(0);
   }
-  Query_log_event qev(thd, STRING_WITH_LEN("COMMIT"), TRUE, FALSE);
-  qev.error_code= 0; // see comment in MYSQL_LOG::write(THD, IO_CACHE)
-  DBUG_RETURN(binlog_end_trans(thd, trans_log, &qev));
+  if (all) 
+  {
+    Query_log_event qev(thd, STRING_WITH_LEN("COMMIT"), TRUE, FALSE);
+    qev.error_code= 0; // see comment in MYSQL_LOG::write(THD, IO_CACHE)
+    DBUG_RETURN(binlog_end_trans(thd, trans_log, &qev));
+  }
+  else
+    DBUG_RETURN(binlog_end_trans(thd, trans_log, &invisible_commit));
 }
 
 static int binlog_rollback(THD *thd, bool all)
@@ -1813,6 +1822,9 @@ bool MYSQL_LOG::write(THD *thd, IO_CACHE *cache, Log_event *commit_event)
   DBUG_ENTER("MYSQL_LOG::write(THD *, IO_CACHE *, Log_event *)");
   VOID(pthread_mutex_lock(&LOCK_log));
 
+  /* NULL would represent nothing to replicate after ROLLBACK */
+  DBUG_ASSERT(commit_event != NULL);
+
   if (likely(is_open()))                       // Should always be true
   {
     uint length;
diff --git a/sql/log_event.cc b/sql/log_event.cc
index 266d6b064bd..cabf4631284 100644
--- a/sql/log_event.cc
+++ b/sql/log_event.cc
@@ -1229,6 +1229,18 @@ bool Query_log_event::write(IO_CACHE* file)
           my_b_safe_write(file, (byte*) query, q_len)) ? 1 : 0;
 }
 
+/*
+  Query_log_event::Query_log_event()
+ 
+  The simplest constructor that could possibly work.  This is used for
+  creating static objects that have a special meaning and are invisible
+  to the log.  
+*/
+Query_log_event::Query_log_event()
+  :Log_event(), data_buf(0)
+{
+}
+
 
 /*
   Query_log_event::Query_log_event()
@@ -1876,6 +1888,21 @@ end:
 
 
 /**************************************************************************
+	Muted_query_log_event methods
+**************************************************************************/
+
+#ifndef MYSQL_CLIENT
+/*
+  Muted_query_log_event::Muted_query_log_event()
+*/
+Muted_query_log_event::Muted_query_log_event()
+  :Query_log_event()
+{
+}
+#endif
+
+
+/**************************************************************************
 	Start_log_event_v3 methods
 **************************************************************************/
 
diff --git a/sql/log_event.h b/sql/log_event.h
index 0e1eb7cd13c..f1b441dedb1 100644
--- a/sql/log_event.h
+++ b/sql/log_event.h
@@ -783,6 +783,7 @@ public:
   void print(FILE* file, PRINT_EVENT_INFO* print_event_info= 0);
 #endif
 
+  Query_log_event();
   Query_log_event(const char* buf, uint event_len,
                   const Format_description_log_event *description_event,
                   Log_event_type event_type);
@@ -806,6 +807,26 @@ public:
   /* Writes derived event-specific part of post header. */
 };
 
+
+/*****************************************************************************
+
+  Muted Query Log Event class
+
+  Pretends to Log SQL queries, but doesn't actually do so.
+
+ ****************************************************************************/
+class Muted_query_log_event: public Query_log_event
+{
+public:
+#ifndef MYSQL_CLIENT
+  Muted_query_log_event();
+
+  bool write(IO_CACHE* file) { return(false); };
+  virtual bool write_post_header_for_derived(IO_CACHE* file) { return FALSE; }
+#endif
+};
+
+
 #ifdef HAVE_REPLICATION
 
 /*****************************************************************************