BUG#48738: Backport patch for Bug 34582 to 5.0 codebase.

From BUG 34582 commit message:

Issuing 'FLUSH LOGS' does not close and reopen indexfile.
Instead a SEEK_SET is performed.
            
This patch makes index file to be closed and reopened whenever a
rotation happens (FLUSH LOGS is issued or binary log exceeds 
maximum configured size).

mysql-test/r/binlog_delete_and_flush_index.result

+RESET MASTER;
+CREATE TABLE t1 (a int);
+### assertion: index file contains regular entries
+SET @index=LOAD_FILE('MYSQLD_DATADIR/master-bin.index');
+master-bin.000001
+
+### assertion: show original binlogs
+show binary logs;
+Log_name	File_size
+master-bin.000001	#
+### assertion: binlog contents from regular entries
+show binlog events from <binlog_start>;
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+master-bin.000001	#	Query	#	#	use `test`; CREATE TABLE t1 (a int)
+FLUSH LOGS;
+### assertion: index file contains renamed binlog and the new one
+SET @index=LOAD_FILE('MYSQLD_DATADIR/master-bin.index');
+master-bin-b34582.000001
+master-bin.000002
+
+### assertion: original binlog content still exists, despite we
+###            renamed and changed the index file 
+show binlog events from <binlog_start>;
+Log_name	Pos	Event_type	Server_id	End_log_pos	Info
+master-bin-b34582.000001	#	Query	#	#	use `test`; CREATE TABLE t1 (a int)
+### assertion: user changed binlog index shows correct entries
+show binary logs;
+Log_name	File_size
+master-bin-b34582.000001	#
+master-bin.000002	#
+DROP TABLE t1;
+### assertion: purging binlogs up to binlog created after instrumenting index file should work
+PURGE BINARY LOGS TO 'master-bin.000002';
+### assertion: show binary logs should only contain latest binlog
+show binary logs;
+Log_name	File_size
+master-bin.000002	#
+### assertion: assert that binlog files were indeed purged (using file_exists calls)
+### assertion: assert that not purged binlog file exists
+### assertion: show index file contents and these should match show binary logs issued above
+SET @index=LOAD_FILE('MYSQLD_DATADIR/master-bin.index');
+master-bin.000002
+
+RESET MASTER;

mysql-test/t/binlog_delete_and_flush_index.test

+# BUG#34582: FLUSH LOGS does not close and reopen the binlog index
+# file
+#
+# WHAT
+# ==== 
+#
+# We want to test that FLUSH LOGS closes and reopens binlog index
+# file.
+#
+# HOW
+# === 
+#
+#  PREPARE:
+#   1. create some binlog events
+#   2. show index content, binlog events and binlog contents 
+#      for mysql-bin.000001
+#   3. copy the mysql-bin.000001 to mysql-bin-b34582.000001
+#   4. change the index file so that mysql-bin.000001 is replaced 
+#      with mysql-bin-b34582.000001
+#   5. FLUSH the logs so that new index is closed and reopened
+#
+#  ASSERTIONS:
+#   1. index file contents shows mysql-bin-b34582.000001 and 
+#      mysql-bin.000002
+#   1. show binary logs shows current index entries
+#   2. binlog contents for mysql-bin-b34582.000001 are displayed
+#   3. Purge binlogs up to the latest one succeeds
+#   4. SHOW BINARY LOGS presents the latest one only after purging
+#   5. Purged binlogs files don't exist in the filesystem
+#   6. Not purged binlog file exists in the filesystem
+#
+#  CLEAN UP:
+#   1. RESET MASTER
+#
+
+-- source include/have_log_bin.inc
+
+RESET MASTER;
+
+-- let $datadir= $MYSQLTEST_VARDIR/log
+-- let $index=$datadir/master-bin.index
+-- chmod 0666 $index
+
+# action: issue one command so that binlog gets some event
+CREATE TABLE t1 (a int);
+
+-- echo ### assertion: index file contains regular entries
+-- replace_regex /[\\\/].*master/MYSQLD_DATADIR\/master/
+-- eval SET @index=LOAD_FILE('$index')
+if (`SELECT convert(@@version_compile_os using latin1)
+                IN ('Win32','Win64','Windows')`)
+{
+  -- disable_query_log
+  -- disable_result_log
+  -- let $a= `SELECT REPLACE (@index, '$datadir\', '')`
+  -- enable_result_log
+  -- enable_query_log
+
+  -- echo $a
+
+}
+if (!`SELECT convert(@@version_compile_os using latin1)
+                 IN ('Win32','Win64','Windows')`)
+{
+  -- disable_query_log
+  -- disable_result_log
+  -- let $a= `SELECT REPLACE (@index, '$datadir/', '')`
+  -- enable_result_log
+  -- enable_query_log
+
+  -- echo $a
+}
+
+--echo ### assertion: show original binlogs
+-- source include/show_binary_logs.inc
+
+--echo ### assertion: binlog contents from regular entries
+-- source include/show_binlog_events.inc
+
+# action: copy binlogs to other names and change entries in index file
+-- copy_file $datadir/master-bin.000001 $datadir/master-bin-b34582.000001
+-- let newbinfile=$datadir/master-bin-b34582.000001
+let INDEX_FILE=$index;
+perl;
+$newbinfile= $ENV{'newbinfile'};
+$file= $ENV{'INDEX_FILE'};
+open(FILE, ">$file") || die "Unable to open $file.";
+truncate(FILE,0);
+print FILE $newbinfile . "\n";
+close ($file);
+EOF
+
+# action: should cause rotation, and creation of new binlogs
+FLUSH LOGS;
+
+# file is not used anymore - remove it (mysql closed on flush logs).
+-- remove_file $datadir/master-bin.000001
+
+-- echo ### assertion: index file contains renamed binlog and the new one
+-- replace_regex /[\\\/].*master/MYSQLD_DATADIR\/master/
+-- eval SET @index=LOAD_FILE('$index')
+if (`SELECT convert(@@version_compile_os using latin1)
+                IN ('Win32','Win64','Windows')`)
+{
+  -- disable_query_log
+  -- disable_result_log
+  -- let $a= `SELECT REPLACE (@index, '$datadir\', '')`
+  -- enable_result_log
+  -- enable_query_log
+
+  -- echo $a
+
+}
+if (!`SELECT convert(@@version_compile_os using latin1)
+                 IN ('Win32','Win64','Windows')`)
+{
+  -- disable_query_log
+  -- disable_result_log
+  -- let $a= `SELECT REPLACE (@index, '$datadir/', '')`
+  -- enable_result_log
+  -- enable_query_log
+
+  -- echo $a
+}
+
+-- echo ### assertion: original binlog content still exists, despite we
+-- echo ###            renamed and changed the index file 
+-- source include/show_binlog_events.inc
+
+-- echo ### assertion: user changed binlog index shows correct entries
+-- source include/show_binary_logs.inc
+
+DROP TABLE t1;
+
+-- echo ### assertion: purging binlogs up to binlog created after instrumenting index file should work
+-- let $current_binlog= query_get_value(SHOW MASTER STATUS, File, 1)
+-- eval PURGE BINARY LOGS TO '$current_binlog'
+
+-- echo ### assertion: show binary logs should only contain latest binlog
+-- source include/show_binary_logs.inc
+
+-- echo ### assertion: assert that binlog files were indeed purged (using file_exists calls)
+-- error 1
+-- file_exists $datadir/master-bin-b34852.000001
+
+-- echo ### assertion: assert that not purged binlog file exists
+-- file_exists $datadir/$current_binlog
+
+-- echo ### assertion: show index file contents and these should match show binary logs issued above
+-- replace_regex /[\\\/].*master/MYSQLD_DATADIR\/master/
+-- eval SET @index=LOAD_FILE('$index')
+if (`SELECT convert(@@version_compile_os using latin1)
+                IN ('Win32','Win64','Windows')`)
+{
+  -- disable_query_log
+  -- disable_result_log
+  -- let $a= `SELECT REPLACE (@index, '$datadir\', '')`
+  -- enable_result_log
+  -- enable_query_log
+
+  -- echo $a
+
+}
+if (!`SELECT convert(@@version_compile_os using latin1)
+                 IN ('Win32','Win64','Windows')`)
+{
+  -- disable_query_log
+  -- disable_result_log
+  -- let $a= `SELECT REPLACE (@index, '$datadir/', '')`
+  -- enable_result_log
+  -- enable_query_log
+
+  -- echo $a
+}
+
+RESET MASTER;

sql/log.cc

@@ -1635,7 +1635,7 @@ void MYSQL_LOG::new_file(bool need_lock)
   old_name=name;
   save_log_type=log_type;
   name=0;				// Don't free name
-  close(LOG_CLOSE_TO_BE_OPENED);
+  close(LOG_CLOSE_TO_BE_OPENED | LOG_CLOSE_INDEX);
 
   /*
      Note that at this point, log_type != LOG_CLOSED (important for is_open()).
@@ -1649,9 +1649,11 @@ void MYSQL_LOG::new_file(bool need_lock)
      Format_description_log_event written at server startup, which should
      trigger temp tables deletion on slaves.
   */
-
-  open(old_name, save_log_type, new_name_ptr,
-       io_cache_type, no_auto_events, max_size, 1);
+  
+  /* reopen index binlog file, BUG#34582 */
+  if (!open_index_file(index_file_name, 0))
+    open(old_name, save_log_type, new_name_ptr, 
+         io_cache_type, no_auto_events, max_size, 1);
   my_free(old_name,MYF(0));
 
 end: