diff --git a/lib/go/camli/index/receive.go b/lib/go/camli/index/receive.go
index 9984d2560..2c8c0f549 100644
--- a/lib/go/camli/index/receive.go
+++ b/lib/go/camli/index/receive.go
@@ -17,6 +17,7 @@ limitations under the License.
 package index
 
 import (
+	"fmt"
 	"io"
 	"log"
 	"os"
@@ -43,10 +44,31 @@ func (ix *Index) ReceiveBlob(blobRef *blobref.BlobRef, source io.Reader) (retsb
 		err = blobserver.ErrCorruptBlob
 		return
 	}
-
 	sniffer.Parse()
+
+	bm := ix.s.BeginBatch()
+
+	err = ix.populateMutation(blobRef, sniffer, bm)
+	if err != nil {
+		return
+	}
+
+	err = ix.s.CommitBatch(bm)
+	if err != nil {
+		return
+	}
+
 	mimeType := sniffer.MimeType()
 	log.Printf("indexer: type=%v; truncated=%v", mimeType, sniffer.IsTruncated())
 
 	return blobref.SizedBlobRef{blobRef, written}, nil
 }
+
+// populateMutation populates keys & values into the provided BatchMutation.
+//
+// the blobref can be trusted at this point (it's been fully consumed
+// and verified to match), and the sniffer has been copied into
+func (ix *Index) populateMutation(br *blobref.BlobRef, sniffer *BlobSniffer, bm BatchMutation) os.Error {
+	bm.Set("have:"+br.String(), fmt.Sprintf("%d", sniffer.Size()))
+	return nil
+}
diff --git a/lib/go/camli/index/sniff.go b/lib/go/camli/index/sniff.go
index f785c0434..f96f90b2f 100644
--- a/lib/go/camli/index/sniff.go
+++ b/lib/go/camli/index/sniff.go
@@ -54,6 +54,10 @@ func (sn *BlobSniffer) Write(d []byte) (int, os.Error) {
 	return len(d), nil
 }
 
+func (sn *BlobSniffer) Size() int64 {
+	return sn.written
+}
+
 func (sn *BlobSniffer) IsTruncated() bool {
 	return sn.written > maxSniffSize
 }