VReplication: Handle large binlog compressed transactions more effici…

…ently (#16328)

Signed-off-by: Matt Lord <[email protected]>

go/mysql/binlog_event.go

@@ -124,9 +124,12 @@ type BinlogEvent interface {
 	// IsWriteRows(), IsUpdateRows(), or IsDeleteRows() returns
 	// true.
 	Rows(BinlogFormat, *TableMap) (Rows, error)
-	// TransactionPayload returns a list of BinlogEvents contained
-	// within the compressed transaction.
-	TransactionPayload(BinlogFormat) ([]BinlogEvent, error)
+	// TransactionPayload returns a TransactionPayload type which provides
+	// a GetNextEvent() method to iterate over the events contained within
+	// the uncompressed payload. You must call Close() when you are done
+	// with the TransactionPayload to ensure that the underlying resources
+	// used are cleaned up.
+	TransactionPayload(BinlogFormat) (*TransactionPayload, error)
 	// NextLogFile returns the name of the next binary log file & pos.
 	// This is only valid if IsRotate() returns true
 	NextLogFile(BinlogFormat) (string, uint64, error)

go/mysql/binlog_event_common.go

@@ -55,8 +55,6 @@ const (
 	BinlogFixedHeaderLen = 19
 	// The offset from 0 where the type is stored as 1 byte.
 	BinlogEventTypeOffset = 4
-	// Offset from 0 where the 4 byte length is stored.
-	BinlogEventLenOffset = 9
 	// Byte length of the checksum suffix when the CRC32 algorithm is used.
 	BinlogCRC32ChecksumLen = 4
 )