diff --git a/include/my_sys.h b/include/my_sys.h
index 62686452fcb..6d2fd3e827e 100644
--- a/include/my_sys.h
+++ b/include/my_sys.h
@@ -607,6 +607,8 @@ static inline size_t my_b_bytes_in_cache(const IO_CACHE *info)
 
 int my_b_copy_to_file    (IO_CACHE *cache, FILE *file, size_t count);
 int my_b_copy_all_to_file(IO_CACHE *cache, FILE *file);
+int my_b_copy_to_cache(IO_CACHE *from_cache, IO_CACHE *to_cache, size_t count);
+int my_b_copy_all_to_cache(IO_CACHE *from_cache, IO_CACHE *to_cache);
 
 my_off_t my_b_append_tell(IO_CACHE* info);
 my_off_t my_b_safe_tell(IO_CACHE* info); /* picks the correct tell() */
diff --git a/mysql-test/main/mysqlbinlog_row_compressed.result b/mysql-test/main/mysqlbinlog_row_compressed.result
index 2cf652655e0..96a0ed61a71 100644
--- a/mysql-test/main/mysqlbinlog_row_compressed.result
+++ b/mysql-test/main/mysqlbinlog_row_compressed.result
@@ -57,11 +57,11 @@ START TRANSACTION
 /*!*/;
 # at 787
 # at 861
-#<date> server id 1  end_log_pos 861 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t1 VALUES (10, 1, 2, 3, 4, 5, 6, 7, "")
-#<date> server id 1  end_log_pos 917 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 917
-#<date> server id 1  end_log_pos 985 CRC32 XXX 	Write_compressed_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_compressed_rows: table id 32 flags: STMT_END_F
 ### INSERT INTO `test`.`t1`
 ### SET
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
@@ -86,11 +86,11 @@ START TRANSACTION
 /*!*/;
 # at 1100
 # at 1176
-#<date> server id 1  end_log_pos 1176 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t1 VALUES (11, 1, 2, 3, 4, 5, 6, 7, NULL)
-#<date> server id 1  end_log_pos 1232 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 1232
-#<date> server id 1  end_log_pos 1299 CRC32 XXX 	Write_compressed_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_compressed_rows: table id 32 flags: STMT_END_F
 ### INSERT INTO `test`.`t1`
 ### SET
 ###   @1=11 /* INT meta=0 nullable=0 is_null=0 */
@@ -115,11 +115,11 @@ START TRANSACTION
 /*!*/;
 # at 1414
 # at 1492
-#<date> server id 1  end_log_pos 1492 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t1 VALUES (12, 1, 2, 3, NULL, 5, 6, 7, "A")
-#<date> server id 1  end_log_pos 1548 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 1548
-#<date> server id 1  end_log_pos 1614 CRC32 XXX 	Write_compressed_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_compressed_rows: table id 32 flags: STMT_END_F
 ### INSERT INTO `test`.`t1`
 ### SET
 ###   @1=12 /* INT meta=0 nullable=0 is_null=0 */
@@ -144,11 +144,11 @@ START TRANSACTION
 /*!*/;
 # at 1729
 # at 1804
-#<date> server id 1  end_log_pos 1804 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t1 VALUES (13, 1, 2, 3, 0, 5, 6, 7, "A")
-#<date> server id 1  end_log_pos 1860 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 1860
-#<date> server id 1  end_log_pos 1927 CRC32 XXX 	Write_compressed_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_compressed_rows: table id 32 flags: STMT_END_F
 ### INSERT INTO `test`.`t1`
 ### SET
 ###   @1=13 /* INT meta=0 nullable=0 is_null=0 */
@@ -173,11 +173,11 @@ START TRANSACTION
 /*!*/;
 # at 2042
 # at 2096
-#<date> server id 1  end_log_pos 2096 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t2 SELECT * FROM t1
-#<date> server id 1  end_log_pos 2152 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
 # at 2152
-#<date> server id 1  end_log_pos 2243 CRC32 XXX 	Write_compressed_rows: table id 33 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_compressed_rows: table id 33 flags: STMT_END_F
 ### INSERT INTO `test`.`t2`
 ### SET
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
@@ -235,11 +235,11 @@ START TRANSACTION
 /*!*/;
 # at 2358
 # at 2424
-#<date> server id 1  end_log_pos 2424 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> UPDATE t2 SET f4=5 WHERE f4>0 or f4 is NULL
-#<date> server id 1  end_log_pos 2480 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
 # at 2480
-#<date> server id 1  end_log_pos 2579 CRC32 XXX 	Update_compressed_rows: table id 33 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Update_compressed_rows: table id 33 flags: STMT_END_F
 ### UPDATE `test`.`t2`
 ### WHERE
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
@@ -316,11 +316,11 @@ START TRANSACTION
 /*!*/;
 # at 2694
 # at 2731
-#<date> server id 1  end_log_pos 2731 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> DELETE FROM t1
-#<date> server id 1  end_log_pos 2787 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 2787
-#<date> server id 1  end_log_pos 2879 CRC32 XXX 	Delete_compressed_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Delete_compressed_rows: table id 32 flags: STMT_END_F
 ### DELETE FROM `test`.`t1`
 ### WHERE
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
@@ -378,11 +378,11 @@ START TRANSACTION
 /*!*/;
 # at 2994
 # at 3031
-#<date> server id 1  end_log_pos 3031 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> DELETE FROM t2
-#<date> server id 1  end_log_pos 3087 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
 # at 3087
-#<date> server id 1  end_log_pos 3172 CRC32 XXX 	Delete_compressed_rows: table id 33 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Delete_compressed_rows: table id 33 flags: STMT_END_F
 ### DELETE FROM `test`.`t2`
 ### WHERE
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
diff --git a/mysql-test/main/mysqlbinlog_row_minimal.result b/mysql-test/main/mysqlbinlog_row_minimal.result
index 69aa91a8903..6871d75a985 100644
--- a/mysql-test/main/mysqlbinlog_row_minimal.result
+++ b/mysql-test/main/mysqlbinlog_row_minimal.result
@@ -55,11 +55,11 @@ START TRANSACTION
 /*!*/;
 # at 834
 # at 908
-#<date> server id 1  end_log_pos 908 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t1 VALUES (10, 1, 2, 3, 4, 5, 6, 7, "")
-#<date> server id 1  end_log_pos 964 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 964
-#<date> server id 1  end_log_pos 1033 CRC32 XXX 	Write_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_rows: table id 32 flags: STMT_END_F
 ### INSERT INTO `test`.`t1`
 ### SET
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
@@ -84,11 +84,11 @@ START TRANSACTION
 /*!*/;
 # at 1148
 # at 1224
-#<date> server id 1  end_log_pos 1224 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t1 VALUES (11, 1, 2, 3, 4, 5, 6, 7, NULL)
-#<date> server id 1  end_log_pos 1280 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 1280
-#<date> server id 1  end_log_pos 1348 CRC32 XXX 	Write_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_rows: table id 32 flags: STMT_END_F
 ### INSERT INTO `test`.`t1`
 ### SET
 ###   @1=11 /* INT meta=0 nullable=0 is_null=0 */
@@ -113,11 +113,11 @@ START TRANSACTION
 /*!*/;
 # at 1463
 # at 1541
-#<date> server id 1  end_log_pos 1541 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t1 VALUES (12, 1, 2, 3, NULL, 5, 6, 7, "A")
-#<date> server id 1  end_log_pos 1597 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 1597
-#<date> server id 1  end_log_pos 1664 CRC32 XXX 	Write_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_rows: table id 32 flags: STMT_END_F
 ### INSERT INTO `test`.`t1`
 ### SET
 ###   @1=12 /* INT meta=0 nullable=0 is_null=0 */
@@ -142,11 +142,11 @@ START TRANSACTION
 /*!*/;
 # at 1779
 # at 1854
-#<date> server id 1  end_log_pos 1854 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t1 VALUES (13, 1, 2, 3, 0, 5, 6, 7, "A")
-#<date> server id 1  end_log_pos 1910 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 1910
-#<date> server id 1  end_log_pos 1980 CRC32 XXX 	Write_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_rows: table id 32 flags: STMT_END_F
 ### INSERT INTO `test`.`t1`
 ### SET
 ###   @1=13 /* INT meta=0 nullable=0 is_null=0 */
@@ -171,11 +171,11 @@ START TRANSACTION
 /*!*/;
 # at 2095
 # at 2149
-#<date> server id 1  end_log_pos 2149 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> INSERT INTO t2 SELECT * FROM t1
-#<date> server id 1  end_log_pos 2205 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
 # at 2205
-#<date> server id 1  end_log_pos 2372 CRC32 XXX 	Write_rows: table id 33 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Write_rows: table id 33 flags: STMT_END_F
 ### INSERT INTO `test`.`t2`
 ### SET
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
@@ -233,11 +233,11 @@ START TRANSACTION
 /*!*/;
 # at 2487
 # at 2553
-#<date> server id 1  end_log_pos 2553 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> UPDATE t2 SET f4=5 WHERE f4>0 or f4 is NULL
-#<date> server id 1  end_log_pos 2609 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
 # at 2609
-#<date> server id 1  end_log_pos 2675 CRC32 XXX 	Update_rows: table id 33 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Update_rows: table id 33 flags: STMT_END_F
 ### UPDATE `test`.`t2`
 ### WHERE
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
@@ -266,11 +266,11 @@ START TRANSACTION
 /*!*/;
 # at 2790
 # at 2827
-#<date> server id 1  end_log_pos 2827 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> DELETE FROM t1
-#<date> server id 1  end_log_pos 2883 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t1` mapped to number num
 # at 2883
-#<date> server id 1  end_log_pos 2937 CRC32 XXX 	Delete_rows: table id 32 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Delete_rows: table id 32 flags: STMT_END_F
 ### DELETE FROM `test`.`t1`
 ### WHERE
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
@@ -296,11 +296,11 @@ START TRANSACTION
 /*!*/;
 # at 3052
 # at 3089
-#<date> server id 1  end_log_pos 3089 CRC32 XXX 	Annotate_rows:
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Annotate_rows:
 #Q> DELETE FROM t2
-#<date> server id 1  end_log_pos 3145 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Table_map: `test`.`t2` mapped to number num
 # at 3145
-#<date> server id 1  end_log_pos 3199 CRC32 XXX 	Delete_rows: table id 33 flags: STMT_END_F
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Delete_rows: table id 33 flags: STMT_END_F
 ### DELETE FROM `test`.`t2`
 ### WHERE
 ###   @1=10 /* INT meta=0 nullable=0 is_null=0 */
diff --git a/mysql-test/main/mysqlbinlog_stmt_compressed.result b/mysql-test/main/mysqlbinlog_stmt_compressed.result
index c0d26f3f9df..6321e74127f 100644
--- a/mysql-test/main/mysqlbinlog_stmt_compressed.result
+++ b/mysql-test/main/mysqlbinlog_stmt_compressed.result
@@ -56,7 +56,7 @@ CREATE TABLE t2 (pk INT PRIMARY KEY, f1 INT, f2 INT, f3 INT, f4 INT, f5 MEDIUMIN
 START TRANSACTION
 /*!*/;
 # at 787
-#<date> server id 1  end_log_pos 915 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
 SET TIMESTAMP=X/*!*/;
 INSERT INTO t1 VALUES (10, 1, 2, 3, 4, 5, 6, 7, "")
 /*!*/;
@@ -71,7 +71,7 @@ COMMIT
 START TRANSACTION
 /*!*/;
 # at 1030
-#<date> server id 1  end_log_pos 1158 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
 SET TIMESTAMP=X/*!*/;
 INSERT INTO t1 VALUES (11, 1, 2, 3, 4, 5, 6, 7, NULL)
 /*!*/;
@@ -86,7 +86,7 @@ COMMIT
 START TRANSACTION
 /*!*/;
 # at 1273
-#<date> server id 1  end_log_pos 1403 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
 SET TIMESTAMP=X/*!*/;
 INSERT INTO t1 VALUES (12, 1, 2, 3, NULL, 5, 6, 7, "A")
 /*!*/;
@@ -101,7 +101,7 @@ COMMIT
 START TRANSACTION
 /*!*/;
 # at 1518
-#<date> server id 1  end_log_pos 1645 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
 SET TIMESTAMP=X/*!*/;
 INSERT INTO t1 VALUES (13, 1, 2, 3, 0, 5, 6, 7, "A")
 /*!*/;
@@ -116,7 +116,7 @@ COMMIT
 START TRANSACTION
 /*!*/;
 # at 1760
-#<date> server id 1  end_log_pos 1868 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
 SET TIMESTAMP=X/*!*/;
 INSERT INTO t2 SELECT * FROM t1
 /*!*/;
@@ -131,7 +131,7 @@ COMMIT
 START TRANSACTION
 /*!*/;
 # at 1983
-#<date> server id 1  end_log_pos 2100 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
 SET TIMESTAMP=X/*!*/;
 UPDATE t2 SET f4=5 WHERE f4>0 or f4 is NULL
 /*!*/;
@@ -146,7 +146,7 @@ COMMIT
 START TRANSACTION
 /*!*/;
 # at 2215
-#<date> server id 1  end_log_pos 2306 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
 SET TIMESTAMP=X/*!*/;
 DELETE FROM t1
 /*!*/;
@@ -161,7 +161,7 @@ COMMIT
 START TRANSACTION
 /*!*/;
 # at 2421
-#<date> server id 1  end_log_pos 2512 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
+#<date> server id 1  end_log_pos 0 CRC32 XXX 	Query_compressed	thread_id=5	exec_time=x	error_code=0	xid=<xid>
 SET TIMESTAMP=X/*!*/;
 DELETE FROM t2
 /*!*/;
diff --git a/mysql-test/main/mysqld--help.result b/mysql-test/main/mysqld--help.result
index 77d6d10b3e6..01ff752b8f2 100644
--- a/mysql-test/main/mysqld--help.result
+++ b/mysql-test/main/mysqld--help.result
@@ -101,6 +101,12 @@ The following specify which files/extra groups are read (specified before remain
  --binlog-ignore-db=name 
  Tells the master that updates to the given database
  should not be logged to the binary log.
+ --binlog-legacy-event-pos 
+ Fill in the end_log_pos field of _all_ events in the
+ binlog, even when doing so costs performance. Can be used
+ in case some old application needs it for backwards
+ compatibility. Setting this option can hurt binlog
+ scalability.
  --binlog-optimize-thread-scheduling 
  Run fast part of group commit in a single thread, to
  optimize kernel thread scheduling. On by default. Disable
@@ -1565,6 +1571,7 @@ binlog-direct-non-transactional-updates FALSE
 binlog-expire-logs-seconds 0
 binlog-file-cache-size 16384
 binlog-format MIXED
+binlog-legacy-event-pos FALSE
 binlog-optimize-thread-scheduling TRUE
 binlog-row-event-max-size 8192
 binlog-row-image FULL
diff --git a/mysql-test/suite/binlog/include/binlog_ioerr.inc b/mysql-test/suite/binlog/include/binlog_ioerr.inc
index da6fb5ac727..b710eccc64b 100644
--- a/mysql-test/suite/binlog/include/binlog_ioerr.inc
+++ b/mysql-test/suite/binlog/include/binlog_ioerr.inc
@@ -17,11 +17,14 @@ CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=innodb;
 INSERT INTO t1 VALUES(0);
 SET @saved_dbug = @@SESSION.debug_dbug;
 SET SESSION debug_dbug='+d,fail_binlog_write_1';
+# The error injection is in the "legacy" code path.
+SET GLOBAL binlog_legacy_event_pos= 1;
 --error ER_ERROR_ON_WRITE
 INSERT INTO t1 VALUES(1);
 --error ER_ERROR_ON_WRITE
 INSERT INTO t1 VALUES(2);
 SET SESSION debug_dbug=@saved_dbug;
+SET GLOBAL binlog_legacy_event_pos= 0;
 INSERT INTO t1 VALUES(3);
 SELECT * FROM t1;
 
diff --git a/mysql-test/suite/binlog/r/binlog_ioerr.result b/mysql-test/suite/binlog/r/binlog_ioerr.result
index e4f00a017ba..aa4042d3f6f 100644
--- a/mysql-test/suite/binlog/r/binlog_ioerr.result
+++ b/mysql-test/suite/binlog/r/binlog_ioerr.result
@@ -4,11 +4,13 @@ CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=innodb;
 INSERT INTO t1 VALUES(0);
 SET @saved_dbug = @@SESSION.debug_dbug;
 SET SESSION debug_dbug='+d,fail_binlog_write_1';
+SET GLOBAL binlog_legacy_event_pos= 1;
 INSERT INTO t1 VALUES(1);
 ERROR HY000: Error writing file 'master-bin' (errno: 28 "No space left on device")
 INSERT INTO t1 VALUES(2);
 ERROR HY000: Error writing file 'master-bin' (errno: 28 "No space left on device")
 SET SESSION debug_dbug=@saved_dbug;
+SET GLOBAL binlog_legacy_event_pos= 0;
 INSERT INTO t1 VALUES(3);
 SELECT * FROM t1;
 a
diff --git a/mysql-test/suite/binlog/t/binlog_killed.test b/mysql-test/suite/binlog/t/binlog_killed.test
index 7c3a262d2c1..271da705c82 100644
--- a/mysql-test/suite/binlog/t/binlog_killed.test
+++ b/mysql-test/suite/binlog/t/binlog_killed.test
@@ -67,7 +67,7 @@ let $rows= `select count(*) from t2  /* must be 2 or 0 */`;
 
 let $MYSQLD_DATADIR= `select @@datadir`;
 --let $binlog_killed_pos=query_get_value(SHOW BINLOG EVENTS, Pos, 6)
---let $binlog_killed_end_log_pos=query_get_value(SHOW BINLOG EVENTS, End_log_pos, 6)
+--let $binlog_killed_end_log_pos=query_get_value(SHOW BINLOG EVENTS, Pos, 7)
 --exec $MYSQL_BINLOG --force-if-open --start-position=$binlog_killed_pos --stop-position=$binlog_killed_end_log_pos $MYSQLD_DATADIR/master-bin.000001 > $MYSQLTEST_VARDIR/tmp/kill_query_calling_sp.binlog
 --replace_result $MYSQLTEST_VARDIR MYSQLTEST_VARDIR
 --disable_result_log
diff --git a/mysql-test/suite/binlog/t/binlog_table_map_optional_metadata.test b/mysql-test/suite/binlog/t/binlog_table_map_optional_metadata.test
index 4577c6c1de1..ea4397306f3 100644
--- a/mysql-test/suite/binlog/t/binlog_table_map_optional_metadata.test
+++ b/mysql-test/suite/binlog/t/binlog_table_map_optional_metadata.test
@@ -275,7 +275,7 @@ INSERT INTO t1 VALUES(2, "b");
 
 # The invalid metadata will case assertion failure on Write_rows_log_event
 # So we need to stop mysqlbinlog before reading Write_rows_log_event.
---let $stop_position= query_get_value(SHOW BINLOG EVENTS FROM $start_pos LIMIT 3, End_log_pos, 3)
+--let $stop_position= query_get_value(SHOW BINLOG EVENTS FROM $start_pos LIMIT 4, Pos, 4)
 --source include/print_optional_metadata.inc
 
 --echo #
@@ -291,7 +291,7 @@ INSERT INTO t1(c_point) VALUES(ST_PointFromText('POINT(10 10)'));
 
 # The invalid metadata will case assertion failure on Write_rows_log_event
 # So we need to stop mysqlbinlog before reading Write_rows_log_event.
---let $stop_position= query_get_value(SHOW BINLOG EVENTS FROM $start_pos LIMIT 3, End_log_pos, 3)
+--let $stop_position= query_get_value(SHOW BINLOG EVENTS FROM $start_pos LIMIT 4, Pos, 4)
 --source include/print_optional_metadata.inc
 
 DROP TABLE t1;
diff --git a/mysql-test/suite/binlog_encryption/binlog_ioerr.result b/mysql-test/suite/binlog_encryption/binlog_ioerr.result
index 2823b7050c3..146bc50c964 100644
--- a/mysql-test/suite/binlog_encryption/binlog_ioerr.result
+++ b/mysql-test/suite/binlog_encryption/binlog_ioerr.result
@@ -4,11 +4,13 @@ CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=innodb;
 INSERT INTO t1 VALUES(0);
 SET @saved_dbug = @@SESSION.debug_dbug;
 SET SESSION debug_dbug='+d,fail_binlog_write_1';
+SET GLOBAL binlog_legacy_event_pos= 1;
 INSERT INTO t1 VALUES(1);
 ERROR HY000: Error writing file 'master-bin' (errno: 28 "No space left on device")
 INSERT INTO t1 VALUES(2);
 ERROR HY000: Error writing file 'master-bin' (errno: 28 "No space left on device")
 SET SESSION debug_dbug=@saved_dbug;
+SET GLOBAL binlog_legacy_event_pos= 0;
 INSERT INTO t1 VALUES(3);
 SELECT * FROM t1;
 a
diff --git a/mysql-test/suite/rpl/r/rpl_checksum_cache.result b/mysql-test/suite/rpl/r/rpl_checksum_cache.result
index e8f221cc181..b908c546ce3 100644
--- a/mysql-test/suite/rpl/r/rpl_checksum_cache.result
+++ b/mysql-test/suite/rpl/r/rpl_checksum_cache.result
@@ -121,13 +121,54 @@ connection slave;
 include/diff_tables.inc [master:test.t1, slave:test.t1]
 include/diff_tables.inc [master:test.t2, slave:test.t2]
 include/diff_tables.inc [master:test.t3, slave:test.t3]
+*** Test switching checksum algorithm while ongoing transactions have pre-computed checksum in their binlog cache ***
+connection master;
+CREATE TABLE t4 (a INT, b INT, c VARCHAR(1024), PRIMARY KEY (a,b)) ENGINE=InnoDB;
+BEGIN;
+INSERT INTO t4 VALUES (1, 1, "small, pre-computed checksums");
+connection server_1;
+BEGIN;
+INSERT INTO t4 VALUES (2, 1, "big, pre-computed checksums");
+set @@global.binlog_checksum = NONE;
+connection master;
+INSERT INTO t4 VALUES (1, 2, "done");
+COMMIT;
+connection server_1;
+INSERT INTO t4 VALUES (2, 22, "done");
+COMMIT;
+connection master;
+BEGIN;
+INSERT INTO t4 VALUES (3, 1, "small, no pre-computed checksums");
+connection server_1;
+BEGIN;
+INSERT INTO t4 VALUES (4, 1, "big, no pre-computed checksums");
+set @@global.binlog_checksum = CRC32;
+connection master;
+INSERT INTO t4 VALUES (3, 2, "done");
+COMMIT;
+connection server_1;
+INSERT INTO t4 VALUES (4, 22, "done");
+COMMIT;
+connection slave;
+*** Test the --binlog-legacy-event-pos option.
+connection master;
+FLUSH BINARY LOGS;
+BEGIN;
+INSERT INTO t4 VALUES (5, 1, "Zero end_log_pos");
+COMMIT;
+set @@global.binlog_legacy_event_pos= 1;
+BEGIN;
+INSERT INTO t4 VALUES (6, 1, "Non-zero end_log_pos");
+COMMIT;
+set @@global.binlog_legacy_event_pos= 0;
+connection slave;
 connection master;
 begin;
 delete from t1;
 delete from t2;
 delete from t3;
 commit;
-drop table t1, t2, t3;
+drop table t1, t2, t3, t4;
 set @@global.binlog_cache_size = @save_binlog_cache_size;
 set @@global.binlog_checksum = @save_binlog_checksum;
 set @@global.master_verify_checksum = @save_master_verify_checksum;
diff --git a/mysql-test/suite/rpl/t/rpl_checksum_cache.test b/mysql-test/suite/rpl/t/rpl_checksum_cache.test
index e04f618b81e..173af8c1d0b 100644
--- a/mysql-test/suite/rpl/t/rpl_checksum_cache.test
+++ b/mysql-test/suite/rpl/t/rpl_checksum_cache.test
@@ -243,6 +243,102 @@ let $diff_tables=master:test.t3, slave:test.t3;
 source include/diff_tables.inc;
 
 
+--echo *** Test switching checksum algorithm while ongoing transactions have pre-computed checksum in their binlog cache ***
+
+--connection master
+CREATE TABLE t4 (a INT, b INT, c VARCHAR(1024), PRIMARY KEY (a,b)) ENGINE=InnoDB;
+
+# Create a couple transactions that will precompute checksums but commit
+# without them.
+
+BEGIN;
+INSERT INTO t4 VALUES (1, 1, "small, pre-computed checksums");
+
+--connection server_1
+BEGIN;
+INSERT INTO t4 VALUES (2, 1, "big, pre-computed checksums");
+--let $i= 20
+--disable_query_log
+while ($i) {
+  eval INSERT INTO t4 VALUES (2, 22-$i, REPEAT("x", FLOOR(RAND()*100) + 831));
+  dec $i;
+}
+--enable_query_log
+
+# Disable checksums dynamically, so MYSQL_BIN_LOG::write_cache() will have
+# to drop the pre-computed checksums.
+set @@global.binlog_checksum = NONE;
+
+--connection master
+INSERT INTO t4 VALUES (1, 2, "done");
+COMMIT;
+--connection server_1
+INSERT INTO t4 VALUES (2, 22, "done");
+COMMIT;
+
+# Create a couple transactions that will not precompute checksums but commit
+# with them.
+
+--connection master
+BEGIN;
+INSERT INTO t4 VALUES (3, 1, "small, no pre-computed checksums");
+
+--connection server_1
+BEGIN;
+INSERT INTO t4 VALUES (4, 1, "big, no pre-computed checksums");
+--let $i= 20
+--disable_query_log
+while ($i) {
+  eval INSERT INTO t4 VALUES (4, 22-$i, REPEAT("x", FLOOR(RAND()*100) + 853));
+  dec $i;
+}
+--enable_query_log
+
+# Ebable checksums dynamically, so MYSQL_BIN_LOG::write_cache() will have
+# to recompute the checksums.
+set @@global.binlog_checksum = CRC32;
+
+--connection master
+INSERT INTO t4 VALUES (3, 2, "done");
+COMMIT;
+--connection server_1
+INSERT INTO t4 VALUES (4, 22, "done");
+COMMIT;
+
+sync_slave_with_master;
+
+
+--echo *** Test the --binlog-legacy-event-pos option.
+--connection master
+FLUSH BINARY LOGS;
+--source include/wait_for_binlog_checkpoint.inc
+
+--let $query_file= query_get_value(SHOW MASTER STATUS, File, 1)
+--let $query_pos= query_get_value(SHOW MASTER STATUS, Position, 1)
+BEGIN;
+INSERT INTO t4 VALUES (5, 1, "Zero end_log_pos");
+COMMIT;
+--let $end_log_pos= query_get_value(SHOW BINLOG EVENTS IN "$query_file" FROM $query_pos LIMIT 3, End_log_pos, 2)
+if ($end_log_pos!=0) {
+  eval SHOW BINLOG EVENTS IN "$query_file";
+  --die Wrong End_log_pos=$end_log_pos, expected zero.
+}
+
+set @@global.binlog_legacy_event_pos= 1;
+--let $query_pos= query_get_value(SHOW MASTER STATUS, Position, 1)
+BEGIN;
+INSERT INTO t4 VALUES (6, 1, "Non-zero end_log_pos");
+COMMIT;
+--let $end_log_pos= query_get_value(SHOW BINLOG EVENTS IN "$query_file" FROM $query_pos LIMIT 3, End_log_pos, 2)
+if ($end_log_pos==0) {
+  eval SHOW BINLOG EVENTS IN "$query_file";
+  --die Wrong End_log_pos=$end_log_pos, expected non-zero.
+}
+set @@global.binlog_legacy_event_pos= 0;
+
+sync_slave_with_master;
+
+
 connection master;
 
 begin;
@@ -251,7 +347,7 @@ delete from t2;
 delete from t3;
 commit;
 
-drop table t1, t2, t3;
+drop table t1, t2, t3, t4;
 set @@global.binlog_cache_size = @save_binlog_cache_size;
 set @@global.binlog_checksum = @save_binlog_checksum;
 set @@global.master_verify_checksum = @save_master_verify_checksum;
diff --git a/mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result b/mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
index 1fb6b245ace..9fca3966e2c 100644
--- a/mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
+++ b/mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result
@@ -462,6 +462,16 @@ NUMERIC_BLOCK_SIZE	NULL
 ENUM_VALUE_LIST	NULL
 READ_ONLY	YES
 COMMAND_LINE_ARGUMENT	NULL
+VARIABLE_NAME	BINLOG_LEGACY_EVENT_POS
+VARIABLE_SCOPE	GLOBAL
+VARIABLE_TYPE	BOOLEAN
+VARIABLE_COMMENT	Fill in the end_log_pos field of _all_ events in the binlog, even when doing so costs performance. Can be used in case some old application needs it for backwards compatibility. Setting this option can hurt binlog scalability.
+NUMERIC_MIN_VALUE	NULL
+NUMERIC_MAX_VALUE	NULL
+NUMERIC_BLOCK_SIZE	NULL
+ENUM_VALUE_LIST	OFF,ON
+READ_ONLY	NO
+COMMAND_LINE_ARGUMENT	OPTIONAL
 VARIABLE_NAME	BINLOG_OPTIMIZE_THREAD_SCHEDULING
 VARIABLE_SCOPE	GLOBAL
 VARIABLE_TYPE	BOOLEAN
diff --git a/mysys/mf_iocache2.c b/mysys/mf_iocache2.c
index 4622b68646e..e134524af97 100644
--- a/mysys/mf_iocache2.c
+++ b/mysys/mf_iocache2.c
@@ -74,6 +74,41 @@ int my_b_copy_all_to_file(IO_CACHE *cache, FILE *file)
   DBUG_RETURN(my_b_copy_to_file(cache, file, SIZE_T_MAX));
 }
 
+/**
+   Similar to above my_b_copy_to_file(), but destination is another IO_CACHE.
+*/
+int
+my_b_copy_to_cache(IO_CACHE *from_cache, IO_CACHE *to_cache,
+                  size_t count)
+{
+  size_t curr_write, bytes_in_cache;
+  DBUG_ENTER("my_b_copy_to_cache");
+
+  bytes_in_cache= my_b_bytes_in_cache(from_cache);
+  do
+  {
+    curr_write= MY_MIN(bytes_in_cache, count);
+    if (my_b_write(to_cache, from_cache->read_pos, curr_write))
+      DBUG_RETURN(1);
+
+    from_cache->read_pos += curr_write;
+    count -= curr_write;
+  } while (count && (bytes_in_cache= my_b_fill(from_cache)));
+  if(from_cache->error == -1)
+    DBUG_RETURN(1);
+  DBUG_RETURN(0);
+}
+
+int my_b_copy_all_to_cache(IO_CACHE *from_cache, IO_CACHE *to_cache)
+{
+  DBUG_ENTER("my_b_copy_all_to_cache");
+  /* Reinit the cache to read from the beginning of the cache */
+  if (reinit_io_cache(from_cache, READ_CACHE, 0L, FALSE, FALSE))
+    DBUG_RETURN(1);
+  DBUG_RETURN(my_b_copy_to_cache(from_cache, to_cache,
+                                 from_cache->end_of_file));
+}
+
 my_off_t my_b_append_tell(IO_CACHE* info)
 {
   /*
diff --git a/sql/log.cc b/sql/log.cc
index b0d1e1eeb34..f4eb94e33fc 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -110,6 +110,16 @@ static const LEX_CSTRING write_error_msg=
     { STRING_WITH_LEN("error writing to the binary log") };
 
 static my_bool opt_optimize_thread_scheduling= TRUE;
+/*
+  The binlog_checksum_options value is accessed protected under LOCK_log. As
+  the checksum option used must be consistent across an entire binlog file,
+  and log rotation is needed whenever this is changed.
+
+  As an exception, event checksums are precomputed using a non-locked read
+  of binlog_checksum_options. Later, the value is checked against the option
+  value, this time under LOCK_log, and checksums are re-computed if the value
+  differs.
+*/
 ulong binlog_checksum_options;
 #ifndef DBUG_OFF
 ulong opt_binlog_dbug_fsync_sleep= 0;
@@ -278,10 +288,21 @@ void make_default_log_name(char **out, const char* log_ext, bool once)
 class binlog_cache_data
 {
 public:
-  binlog_cache_data(): before_stmt_pos(MY_OFF_T_UNDEF), m_pending(0), status(0),
-  incident(FALSE), saved_max_binlog_cache_size(0), ptr_binlog_cache_use(0),
+  binlog_cache_data(bool precompute_checksums_):
+  before_stmt_pos(MY_OFF_T_UNDEF), m_pending(0), status(0),
+  incident(FALSE), precompute_checksums(precompute_checksums_),
+  saved_max_binlog_cache_size(0), ptr_binlog_cache_use(0),
   ptr_binlog_cache_disk_use(0)
-  { }
+  {
+    /*
+      Read the current checksum setting. We will use this setting to decide
+      whether to pre-compute checksums in the cache. Then when writing the cache
+      to the actual binlog, another check will be made and checksums recomputed
+      in the unlikely case that the setting changed meanwhile.
+    */
+    checksum_opt= !precompute_checksums_ ? BINLOG_CHECKSUM_ALG_OFF :
+      (enum_binlog_checksum_alg)binlog_checksum_options;
+  }
   
   ~binlog_cache_data()
   {
@@ -333,6 +354,8 @@ public:
     bool truncate_file= (cache_log.file != -1 &&
                          my_b_write_tell(&cache_log) > CACHE_FILE_TRUNC_SIZE);
     truncate(0,1);                              // Forget what's in cache
+    checksum_opt= !precompute_checksums ? BINLOG_CHECKSUM_ALG_OFF :
+      (enum_binlog_checksum_alg)binlog_checksum_options;
     if (!cache_was_empty)
       compute_statistics();
     if (truncate_file)
@@ -431,12 +454,23 @@ private:
   */
   uint32 status;
 
+public:
+  /*
+    The algorithm (if any) used to pre-compute checksums in the cache.
+    Initialized from binlog_checksum_options when the cache is reset.
+  */
+  enum_binlog_checksum_alg checksum_opt;
+
+private:
   /*
     This indicates that some events did not get into the cache and most likely
     it is corrupted.
   */ 
   bool incident;
 
+  /* Whether the caller requested precomputing checksums. */
+  bool precompute_checksums;
+
   /**
     This function computes binlog cache and disk usage.
   */
@@ -489,7 +523,10 @@ private:
       delete pending();
       set_pending(0);
     }
-    my_bool res= reinit_io_cache(&cache_log, WRITE_CACHE, pos, 0, reset_cache);
+#ifndef DBUG_OFF
+    my_bool res=
+#endif
+      reinit_io_cache(&cache_log, WRITE_CACHE, pos, 0, reset_cache);
     DBUG_ASSERT(res == 0);
     cache_log.end_of_file= saved_max_binlog_cache_size;
   }
@@ -503,6 +540,8 @@ class online_alter_cache_data: public Sql_alloc, public ilist_node<>,
   public binlog_cache_data
 {
 public:
+  online_alter_cache_data() : binlog_cache_data(false),
+    hton(nullptr), sink_log(nullptr), sv_list(nullptr) { }
   void store_prev_position()
   {
     before_stmt_pos= my_b_write_tell(&cache_log);
@@ -525,6 +564,38 @@ void Log_event_writer::set_incident()
 }
 
 
+/**
+   Select if and how to write checksum for an event written to the binlog.
+
+    - When writing directly to the binlog, the user-configured checksum option
+      is used.
+    - When writing to a transaction or statement cache, we have
+      binlog_cache_data that contains the checksum option to use (pre-computed
+      checksums).
+    - Otherwise, no checksum used.
+*/
+enum_binlog_checksum_alg
+Log_event::select_checksum_alg(const binlog_cache_data *data)
+{
+  if (cache_type == Log_event::EVENT_NO_CACHE)
+  {
+    DBUG_ASSERT(!data);
+    /*
+      When we're selecting the checksum algorithm to write directly to the
+      actual binlog, we must be holding the LOCK_log, otherwise the checksum
+      configuration could change just after we read it.
+    */
+    mysql_mutex_assert_owner(mysql_bin_log.get_log_lock());
+    return (enum_binlog_checksum_alg)binlog_checksum_options;
+  }
+
+  if (data)
+    return data->checksum_opt;
+
+  return BINLOG_CHECKSUM_ALG_OFF;
+}
+
+
 class binlog_cache_mngr {
 public:
   binlog_cache_mngr(my_off_t param_max_binlog_stmt_cache_size,
@@ -532,8 +603,10 @@ public:
                     ulong *param_ptr_binlog_stmt_cache_use,
                     ulong *param_ptr_binlog_stmt_cache_disk_use,
                     ulong *param_ptr_binlog_cache_use,
-                    ulong *param_ptr_binlog_cache_disk_use)
-    : last_commit_pos_offset(0), using_xa(FALSE), xa_xid(0)
+                    ulong *param_ptr_binlog_cache_disk_use,
+                    bool precompute_checksums)
+    : stmt_cache(precompute_checksums), trx_cache(precompute_checksums),
+      last_commit_pos_offset(0), using_xa(FALSE), xa_xid(0)
   {
      stmt_cache.set_binlog_cache_info(param_max_binlog_stmt_cache_size,
                                       param_ptr_binlog_stmt_cache_use,
@@ -5744,28 +5817,26 @@ end2:
 }
 
 bool Event_log::write_event(Log_event *ev, binlog_cache_data *data,
-                                IO_CACHE *file)
+                            IO_CACHE *file)
 {
-  return write_event(ev, ev->select_checksum_alg(), data, file);
+  return write_event(ev, ev->select_checksum_alg(data), data, file);
 }
 
 bool MYSQL_BIN_LOG::write_event(Log_event *ev)
 {
-  return write_event(ev, ev->select_checksum_alg(), 0, &log_file);
+  return write_event(ev, ev->select_checksum_alg(NULL), 0, &log_file);
 }
 
-bool MYSQL_BIN_LOG::write_event(Log_event *ev,
-                                enum_binlog_checksum_alg checksum_alg,
-                                binlog_cache_data *cache_data, IO_CACHE *file)
+bool Event_log::write_event(Log_event *ev,
+                            enum_binlog_checksum_alg checksum_alg,
+                            binlog_cache_data *cache_data, IO_CACHE *file)
 {
-  Log_event_writer writer(file, 0, checksum_alg, &crypto);
+  Log_event_writer writer(file, cache_data, checksum_alg, &crypto);
   if (crypto.scheme && file == &log_file)
   {
     writer.ctx= alloca(crypto.ctx_size);
     writer.set_encrypted_writer();
   }
-  if (cache_data)
-    cache_data->add_status(ev->logged_status());
   return writer.write(ev);
 }
 
@@ -6041,7 +6112,7 @@ bool stmt_has_updated_non_trans_table(const THD* thd)
   binlog_hton, which has internal linkage.
 */
 
-binlog_cache_mngr *binlog_setup_cache_mngr()
+static binlog_cache_mngr *binlog_setup_cache_mngr(THD *thd)
 {
   auto *cache_mngr= (binlog_cache_mngr*) my_malloc(key_memory_binlog_cache_mngr,
                                   sizeof(binlog_cache_mngr),
@@ -6056,13 +6127,22 @@ binlog_cache_mngr *binlog_setup_cache_mngr()
     return NULL;
   }
 
+  /*
+    Don't attempt to precompute checksums if:
+     - Disabled by user request, --binlog-legacy-event-pos
+     - Binlog is encrypted, cannot use precomputed checksums
+     - WSREP/Galera.
+  */
+  bool precompute_checksums=
+    !WSREP_NNULL(thd) && !encrypt_binlog && !opt_binlog_legacy_event_pos;
   cache_mngr= new (cache_mngr)
           binlog_cache_mngr(max_binlog_stmt_cache_size,
                             max_binlog_cache_size,
                             &binlog_stmt_cache_use,
                             &binlog_stmt_cache_disk_use,
                             &binlog_cache_use,
-                            &binlog_cache_disk_use);
+                            &binlog_cache_disk_use,
+                            precompute_checksums);
 
   return cache_mngr;
 }
@@ -6075,7 +6155,7 @@ binlog_cache_mngr *THD::binlog_setup_trx_data()
 
   if (!cache_mngr)
   {
-    cache_mngr= binlog_setup_cache_mngr();
+    cache_mngr= binlog_setup_cache_mngr(this);
     thd_set_ha_data(this, binlog_hton, cache_mngr);
   }
 
@@ -6405,7 +6485,8 @@ bool MYSQL_BIN_LOG::write_table_map(THD *thd, TABLE *table, bool with_annotate)
   binlog_cache_data *cache_data= (cache_mngr->
                                   get_binlog_cache_data(is_transactional));
   IO_CACHE *file= &cache_data->cache_log;
-  Log_event_writer writer(file, cache_data, the_event.select_checksum_alg(), NULL);
+  Log_event_writer writer(file, cache_data,
+                          the_event.select_checksum_alg(cache_data), NULL);
 
   if (with_annotate)
     if (thd->binlog_write_annotated_row(&writer))
@@ -6592,7 +6673,7 @@ Event_log::flush_and_set_pending_rows_event(THD *thd, Rows_log_event* event,
   if (Rows_log_event* pending= cache_data->pending())
   {
     Log_event_writer writer(&cache_data->cache_log, cache_data,
-                            pending->select_checksum_alg(), NULL);
+                            pending->select_checksum_alg(cache_data), NULL);
 
     /*
       Write pending event to the cache.
@@ -7875,21 +7956,36 @@ int Event_log::write_cache_raw(THD *thd, IO_CACHE *cache)
     events prior to fill in the binlog cache.
 */
 
-int Event_log::write_cache(THD *thd, IO_CACHE *cache)
+int Event_log::write_cache(THD *thd, binlog_cache_data *cache_data)
 {
   DBUG_ENTER("Event_log::write_cache");
-
+  IO_CACHE *cache= &cache_data->cache_log;
   mysql_mutex_assert_owner(&LOCK_log);
+
+  /*
+    If possible, just copy the cache over byte-by-byte with pre-computed
+    checksums.
+  */
+  if (likely(binlog_checksum_options == (ulong)cache_data->checksum_opt) &&
+      likely(!crypto.scheme) &&
+      likely(!opt_binlog_legacy_event_pos))
+  {
+    int res= my_b_copy_all_to_cache(cache, &log_file);
+    status_var_add(thd->status_var.binlog_bytes_written, my_b_tell(cache));
+    DBUG_RETURN(res ? ER_ERROR_ON_WRITE : 0);
+  }
+
   if (reinit_io_cache(cache, READ_CACHE, 0, 0, 0))
     DBUG_RETURN(ER_ERROR_ON_WRITE);
   /* Amount of remaining bytes in the IO_CACHE read buffer. */
-  size_t group;
-  size_t end_log_pos_inc= 0; // each event processed adds BINLOG_CHECKSUM_LEN 2 t
+  size_t log_file_pos;
   uchar header_buf[LOG_EVENT_HEADER_LEN];
   Log_event_writer writer(get_log_file(), 0,
                           (enum_binlog_checksum_alg)binlog_checksum_options,
                           &crypto);
   uint checksum_len= writer.checksum_len;
+  uint old_checksum_len= (cache_data->checksum_opt != BINLOG_CHECKSUM_ALG_OFF) ?
+    BINLOG_CHECKSUM_LEN : 0;
   int err= 0;
 
   if (crypto.scheme)
@@ -7915,7 +8011,7 @@ int Event_log::write_cache(THD *thd, IO_CACHE *cache)
     split.
   */
 
-  group= (size_t)my_b_tell(get_log_file());
+  log_file_pos= (size_t)my_b_tell(get_log_file());
   for (;;)
   {
     /*
@@ -7936,18 +8032,18 @@ int Event_log::write_cache(THD *thd, IO_CACHE *cache)
 
     /* Adjust the length and end_log_pos appropriately. */
     uint ev_len= uint4korr(&header_buf[EVENT_LEN_OFFSET]); // netto len
-    DBUG_ASSERT(ev_len >= LOG_EVENT_HEADER_LEN);
-    if (unlikely(ev_len < LOG_EVENT_HEADER_LEN))
+    DBUG_ASSERT(ev_len >= LOG_EVENT_HEADER_LEN + old_checksum_len);
+    if (unlikely(ev_len < LOG_EVENT_HEADER_LEN + old_checksum_len))
       goto error_in_read;
-    int4store(&header_buf[EVENT_LEN_OFFSET], ev_len + checksum_len);
-    end_log_pos_inc += checksum_len;
-    size_t val= uint4korr(&header_buf[LOG_POS_OFFSET]) + group + end_log_pos_inc;
-    int4store(&header_buf[LOG_POS_OFFSET], val);
+    uint new_len= ev_len - old_checksum_len + checksum_len;
+    int4store(&header_buf[EVENT_LEN_OFFSET], new_len);
+    log_file_pos+= new_len;
+    int4store(&header_buf[LOG_POS_OFFSET], log_file_pos);
 
     /* Write the header to the binlog. */
     if (writer.write_header(header_buf, LOG_EVENT_HEADER_LEN))
       goto error_in_write;
-    ev_len-= LOG_EVENT_HEADER_LEN;
+    ev_len-= (LOG_EVENT_HEADER_LEN + old_checksum_len);
 
     /* Write the rest of the event. */
     size_t length= my_b_bytes_in_cache(cache);
@@ -7965,7 +8061,12 @@ int Event_log::write_cache(THD *thd, IO_CACHE *cache)
       length-= chunk;
       ev_len-= chunk;
     }
-
+    /*
+      Discard any old precomputed checksum len (any needed checksum will be
+      written by writer.write_footer()).
+    */
+    if (old_checksum_len > 0 && my_b_read(cache, header_buf, old_checksum_len))
+        goto error_in_read;
     if (writer.write_footer())
       goto error_in_write;
 
@@ -9090,7 +9191,7 @@ MYSQL_BIN_LOG::write_transaction_or_stmt(group_commit_entry *entry,
     DBUG_RETURN(ER_ERROR_ON_WRITE);
 
   if (entry->using_stmt_cache && !mngr->stmt_cache.empty() &&
-      write_cache(entry->thd, mngr->get_binlog_cache_log(FALSE)))
+      write_cache(entry->thd, mngr->get_binlog_cache_data(FALSE)))
   {
     entry->error_cache= &mngr->stmt_cache.cache_log;
     DBUG_RETURN(ER_ERROR_ON_WRITE);
@@ -9101,7 +9202,7 @@ MYSQL_BIN_LOG::write_transaction_or_stmt(group_commit_entry *entry,
     DBUG_EXECUTE_IF("crash_before_writing_xid",
                     {
                       if ((write_cache(entry->thd,
-                                       mngr->get_binlog_cache_log(TRUE))))
+                                       mngr->get_binlog_cache_data(TRUE))))
                         DBUG_PRINT("info", ("error writing binlog cache"));
                       else
                         flush_and_sync(0);
@@ -9110,7 +9211,7 @@ MYSQL_BIN_LOG::write_transaction_or_stmt(group_commit_entry *entry,
                       DBUG_SUICIDE();
                     });
 
-    if (write_cache(entry->thd, mngr->get_binlog_cache_log(TRUE)))
+    if (write_cache(entry->thd, mngr->get_binlog_cache_data(TRUE)))
     {
       entry->error_cache= &mngr->trx_cache.cache_log;
       DBUG_RETURN(ER_ERROR_ON_WRITE);
@@ -11728,6 +11829,7 @@ int TC_LOG_BINLOG::recover(LOG_INFO *linfo, const char *last_log_name,
   char binlog_checkpoint_name[FN_REFLEN];
   bool binlog_checkpoint_found;
   IO_CACHE log;
+  IO_CACHE *cur_log;
   File file= -1;
   const char *errmsg;
 #ifdef HAVE_REPLICATION
@@ -11774,12 +11876,16 @@ int TC_LOG_BINLOG::recover(LOG_INFO *linfo, const char *last_log_name,
   */
 
   binlog_checkpoint_found= false;
+  cur_log= first_log;
   for (round= 1;;)
   {
-    while ((ev= Log_event::read_log_event(round == 1 ? first_log : &log,
-                                          fdle, opt_master_verify_checksum))
+    while ((ev= Log_event::read_log_event(cur_log, fdle,
+                                          opt_master_verify_checksum))
            && ev->is_valid())
     {
+#ifdef HAVE_REPLICATION
+      my_off_t end_pos= my_b_tell(cur_log);
+#endif
       enum Log_event_type typ= ev->get_type_code();
       switch (typ)
       {
@@ -11796,7 +11902,7 @@ int TC_LOG_BINLOG::recover(LOG_INFO *linfo, const char *last_log_name,
             member->decided_to_commit= true;
         }
 #else
-        if (ctx.decide_or_assess(member, round, fdle, linfo, ev->log_pos))
+        if (ctx.decide_or_assess(member, round, fdle, linfo, end_pos))
           goto err2;
 #endif
       }
@@ -11897,11 +12003,12 @@ int TC_LOG_BINLOG::recover(LOG_INFO *linfo, const char *last_log_name,
           goto err2;
         ctx.last_gtid_valid= false;
       }
-      ctx.prev_event_pos= ev->log_pos;
+      ctx.prev_event_pos= end_pos;
 #endif
       delete ev;
       ev= NULL;
     } // end of while
+    cur_log= &log;
 
     /*
       If the last binlog checkpoint event points to an older log, we have to
diff --git a/sql/log.h b/sql/log.h
index a4c4fd6cd74..2ba6ffa2b79 100644
--- a/sql/log.h
+++ b/sql/log.h
@@ -402,7 +402,7 @@ public:
                                        bool is_transactional);
   void set_write_error(THD *thd, bool is_transactional);
   static bool check_write_error(THD *thd);
-  int write_cache(THD *thd, IO_CACHE *cache);
+  int write_cache(THD *thd, binlog_cache_data *cache_data);
   int write_cache_raw(THD *thd, IO_CACHE *cache);
   char* get_name() { return name; }
   void cleanup()
@@ -427,6 +427,7 @@ public:
                                    bool encrypt, bool dont_set_created,
                                    bool is_relay_log);
 
+  bool write_event(Log_event *ev, binlog_cache_data *data, IO_CACHE *file);
   bool write_event(Log_event *ev, enum enum_binlog_checksum_alg checksum_alg,
                    binlog_cache_data *data, IO_CACHE *file);
 };
@@ -994,7 +995,6 @@ public:
 
   using Event_log::write_event;
 
-  bool write_event(Log_event *ev, binlog_cache_data *data, IO_CACHE *file);
   bool write_event(Log_event *ev, enum enum_binlog_checksum_alg checksum_alg)
   {
     return write_event(ev, checksum_alg, 0, &log_file);
diff --git a/sql/log_event.cc b/sql/log_event.cc
index 7b92896fddf..d7439fc0a67 100644
--- a/sql/log_event.cc
+++ b/sql/log_event.cc
@@ -720,7 +720,7 @@ Log_event::Log_event(const uchar *buf,
                      const Format_description_log_event* description_event)
   :temp_buf(0), exec_time(0), cache_type(Log_event::EVENT_INVALID_CACHE)
 #ifndef MYSQL_CLIENT
-    , slave_exec_mode(SLAVE_EXEC_MODE_STRICT),
+    , slave_exec_mode(SLAVE_EXEC_MODE_STRICT)
 #endif
 {
 #ifndef MYSQL_CLIENT
diff --git a/sql/log_event.h b/sql/log_event.h
index 3e25209e199..16f16e50169 100644
--- a/sql/log_event.h
+++ b/sql/log_event.h
@@ -1473,7 +1473,7 @@ public:
   bool write_footer(Log_event_writer *writer)
   { return writer->write_footer(); }
 
-  enum_binlog_checksum_alg select_checksum_alg();
+  enum_binlog_checksum_alg select_checksum_alg(const binlog_cache_data *data);
 
   virtual bool write(Log_event_writer *writer)
   {
diff --git a/sql/log_event_server.cc b/sql/log_event_server.cc
index 8280488a255..6b826861f3c 100644
--- a/sql/log_event_server.cc
+++ b/sql/log_event_server.cc
@@ -687,24 +687,6 @@ void Log_event::init_show_field_list(THD *thd, List<Item>* field_list)
                         mem_root);
 }
 
-/**
-   Select if and how to write checksum for an event written to the binlog.
-   It returns the actively configured binlog checksum option, unless the event
-   is being written to a cache (in which case the checksum, if any, is added
-   later when the cache is copied to the real binlog).
-*/
-enum_binlog_checksum_alg Log_event::select_checksum_alg()
-{
-  if (cache_type == Log_event::EVENT_NO_CACHE)
-    return (enum_binlog_checksum_alg)binlog_checksum_options;
-
-  DBUG_ASSERT(get_type_code() != ROTATE_EVENT &&
-              get_type_code() != STOP_EVENT &&
-              get_type_code() != FORMAT_DESCRIPTION_EVENT);
-
-  return BINLOG_CHECKSUM_ALG_OFF;
-}
-
 int Log_event_writer::write_internal(const uchar *pos, size_t len)
 {
   DBUG_ASSERT(!ctx || encrypt_or_write == &Log_event_writer::encrypt_and_write);
@@ -857,11 +839,17 @@ bool Log_event::write_header(Log_event_writer *writer, size_t event_data_length)
     change the position
   */
 
-  if (is_artificial_event())
+  if (is_artificial_event() ||
+      cache_type == Log_event::EVENT_STMT_CACHE ||
+      cache_type == Log_event::EVENT_TRANSACTIONAL_CACHE)
   {
     /*
       Artificial events are automatically generated and do not exist
       in master's binary log, so log_pos should be set to 0.
+
+      Events written through transaction or statement cache have log_pos set
+      to 0 so that they can be copied directly to the binlog without having
+      to compute the real end_log_pos.
     */
     log_pos= 0;
   }
diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 8cc3ad51ee9..875dd8faf6b 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -764,6 +764,7 @@ char *relay_log_info_file, *report_user, *report_password, *report_host;
 char *opt_relay_logname = 0, *opt_relaylog_index_name=0;
 char *opt_logname, *opt_slow_logname, *opt_bin_logname;
 char *opt_binlog_index_name=0;
+my_bool opt_binlog_legacy_event_pos= FALSE;
 
 /* Static variables */
 
diff --git a/sql/mysqld.h b/sql/mysqld.h
index 69cfc0cad56..dbc92f3d189 100644
--- a/sql/mysqld.h
+++ b/sql/mysqld.h
@@ -173,6 +173,7 @@ extern ulong delay_key_write_options;
 extern char *opt_logname, *opt_slow_logname, *opt_bin_logname, 
             *opt_relay_logname;
 extern char *opt_binlog_index_name;
+extern my_bool opt_binlog_legacy_event_pos;
 extern char *opt_backup_history_logname, *opt_backup_progress_logname,
             *opt_backup_settings_name;
 extern const char *log_output_str;
diff --git a/sql/privilege.h b/sql/privilege.h
index 058f3be67c2..28b6868a20b 100644
--- a/sql/privilege.h
+++ b/sql/privilege.h
@@ -363,6 +363,9 @@ constexpr privilege_t PRIV_SET_SYSTEM_GLOBAL_VAR_BINLOG_COMMIT_WAIT_USEC=
 constexpr privilege_t PRIV_SET_SYSTEM_GLOBAL_VAR_BINLOG_ROW_METADATA=
   BINLOG_ADMIN_ACL;
 
+constexpr privilege_t PRIV_SET_SYSTEM_GLOBAL_VAR_BINLOG_LEGACY_EVENT_POS=
+  SUPER_ACL | BINLOG_ADMIN_ACL;
+
 constexpr privilege_t PRIV_SET_SYSTEM_GLOBAL_VAR_EXPIRE_LOGS_DAYS=
   BINLOG_ADMIN_ACL;
 
diff --git a/sql/rpl_record.cc b/sql/rpl_record.cc
index 6098dc7daff..6e0af3ce103 100644
--- a/sql/rpl_record.cc
+++ b/sql/rpl_record.cc
@@ -349,7 +349,7 @@ int unpack_row(const rpl_group_info *rgi, TABLE *table, uint const colcnt,
   st.next_null_byte();
   if (!rpl_data.is_online_alter())
   {
-    Field *result_field;
+    Field *result_field= NULL;
     for (; i < colcnt && (result_field= table->field[i]); i++)
     {
       /*
@@ -439,7 +439,10 @@ int unpack_row(const rpl_group_info *rgi, TABLE *table, uint const colcnt,
     {
       DBUG_ASSERT(bitmap_is_set(cols, i));
       Field *f= conv_table->field[i];
-      bool result= unpack_field(tabledef, f, &st, i);
+#ifndef DBUG_OFF
+      bool result=
+#endif
+        unpack_field(tabledef, f, &st, i);
       DBUG_ASSERT(result);
     }
 
diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index ebb64b340b0..33c7284a343 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -3505,6 +3505,19 @@ Sys_master_verify_checksum(
        GLOBAL_VAR(opt_master_verify_checksum), CMD_LINE(OPT_ARG),
        DEFAULT(FALSE));
 
+
+static Sys_var_on_access_global<Sys_var_mybool,
+                           PRIV_SET_SYSTEM_GLOBAL_VAR_BINLOG_LEGACY_EVENT_POS>
+Sys_binlog_legacy_event_pos(
+       "binlog_legacy_event_pos",
+       "Fill in the end_log_pos field of _all_ events in the binlog, even when "
+       "doing so costs performance. Can be used in case some old application needs "
+       "it for backwards compatibility. Setting this option can hurt binlog "
+       "scalability.",
+       GLOBAL_VAR(opt_binlog_legacy_event_pos), CMD_LINE(OPT_ARG),
+       DEFAULT(FALSE));
+
+
 /* These names must match RPL_SKIP_XXX #defines in slave.h. */
 static const char *replicate_events_marked_for_skip_names[]= {
   "REPLICATE", "FILTER_ON_SLAVE", "FILTER_ON_MASTER", 0