Reset internal buffer when rows.Close() is called.

Fixes #903

Author: methane

buffer.go

@@ -37,6 +37,27 @@ func newBuffer(nc net.Conn) buffer {
 	}
 }
 
+// discard trims b.buf[:b.idx] to prohibit it reused.
+//
+// This is required by Rows.Close().
+// See https://github.com/golang/go/commit/651ddbdb5056ded455f47f9c494c67b389622a47
+func (b *buffer) discard() {
+	if len(b.buf)-b.idx >= defaultBufSize {
+		b.buf = b.buf[b.idx:]
+		b.idx = 0
+		return
+	}
+
+	bufSize := defaultBufSize
+	if bufSize < b.length {
+		bufSize = b.length
+	}
+	newBuf := make([]byte, bufSize)
+	copy(newBuf, b.buf[b.idx:b.idx+b.length])
+	b.buf = newBuf
+	b.idx = 0
+}
+
 // fill reads into the buffer until at least _need_ bytes are in it
 func (b *buffer) fill(need int) error {
 	n := b.length

rows.go

@@ -111,6 +111,10 @@ func (rows *mysqlRows) Close() (err error) {
 		return err
 	}
 
+	// We can't reuse receive buffer when rows.Close() is called.
+	// See https://github.com/golang/go/commit/651ddbdb5056ded455f47f9c494c67b389622a47
+	mc.buf.discard()
+
 	// Remove unread packets from stream
 	if !rows.rs.done {
 		err = mc.readUntilEOF()