The next_position value in the binlog event header is 4 bytes

Boy, MySQL SURE IS FUN! Signed-off-by: Matt Lord <[email protected]>
vitessio · Jan 7, 2025 · 6731e1e · 6731e1e
1 parent bb933e0
commit 6731e1e
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Showing 3 changed files with 7 additions and 6 deletions.
diff --git a/go/mysql/binlog_event_common.go b/go/mysql/binlog_event_common.go
@@ -47,7 +47,7 @@ import (
 //	+----------------------------+
 //	| extra_headers    19 : x-19 |
 //	+============================+
-//	http://dev.mysql.com/doc/internals/en/event-header-fields.html
+//	https://dev.mysql.com/doc/dev/mysql-server/8.0.40/page_protocol_replication_binlog_event.html#sect_protocol_replication_binlog_event_header
 type binlogEvent []byte
 
 const (

diff --git a/go/mysql/binlog_event_filepos.go b/go/mysql/binlog_event_filepos.go
@@ -75,12 +75,13 @@ func (ev *filePosBinlogEvent) StripChecksum(f BinlogFormat) (BinlogEvent, []byte
 
 // nextPosition returns the next file position of the binlog.
 // If no information is available, it returns 0.
-func (ev *filePosBinlogEvent) nextPosition(f BinlogFormat) uint64 {
+func (ev *filePosBinlogEvent) nextPosition(f BinlogFormat) uint32 {
 	if f.HeaderLength <= 13 {
 		// Dead code. This is just a failsafe.
 		return 0
 	}
-	return binary.LittleEndian.Uint64(ev.Bytes()[13:21])
+	// The header only uses 4 bytes for the next_position.
+	return binary.LittleEndian.Uint32(ev.Bytes()[13:17])
 }
 
 // rotate implements BinlogEvent.Rotate().

diff --git a/go/mysql/flavor_filepos.go b/go/mysql/flavor_filepos.go
@@ -191,21 +191,21 @@ func (flv *filePosFlavor) readBinlogEvent(c *Conn) (BinlogEvent, error) {
 			eDeleteRowsEventV0, eDeleteRowsEventV1, eDeleteRowsEventV2,
 			eUpdateRowsEventV0, eUpdateRowsEventV1, eUpdateRowsEventV2:
 			flv.savedEvent = event
-			return newFilePosGTIDEvent(flv.file, event.nextPosition(flv.format), event.Timestamp()), nil
+			return newFilePosGTIDEvent(flv.file, uint64(event.nextPosition(flv.format)), event.Timestamp()), nil
 		case eQueryEvent:
 			q, err := event.Query(flv.format)
 			if err == nil && strings.HasPrefix(q.SQL, "#") {
 				continue
 			}
 			flv.savedEvent = event
-			return newFilePosGTIDEvent(flv.file, event.nextPosition(flv.format), event.Timestamp()), nil
+			return newFilePosGTIDEvent(flv.file, uint64(event.nextPosition(flv.format)), event.Timestamp()), nil
 		default:
 			// For unrecognized events, send a fake "repair" event so that
 			// the position gets transmitted.
 			if !flv.format.IsZero() {
 				if v := event.nextPosition(flv.format); v != 0 {
 					flv.savedEvent = newFilePosQueryEvent("repair", event.Timestamp())
-					return newFilePosGTIDEvent(flv.file, v, event.Timestamp()), nil
+					return newFilePosGTIDEvent(flv.file, uint64(v), event.Timestamp()), nil
 				}
 			}
 		}