Don't set atx version in migration 18 (#6011)

## Motivation

Speedup the 18th migration of state the DB.

sql/atxs/atxs.go

@@ -390,6 +390,11 @@ func getBlob(ctx context.Context, db sql.Executor, id []byte, blob *sql.Blob) (t
 		return 0, fmt.Errorf("%w: atx %s", sql.ErrNotFound, types.BytesToATXID(id))
 	}
 
+	// The migration adding the version column does not set it to 1 for existing ATXs.
+	// Thus, both values 0 and 1 mean V1.
+	if version == 0 {
+		version = types.AtxV1
+	}
 	return version, nil
 }
 

sql/atxs/atxs_test.go

@@ -615,6 +615,24 @@ func TestLoadBlob(t *testing.T) {
 	require.Equal(t, []int{len(blob1.Bytes), -1, len(blob2.Bytes)}, blobSizes)
 }
 
+func TestLoadBlob_DefaultsToV1(t *testing.T) {
+	db := sql.InMemory()
+
+	sig, err := signing.NewEdSigner()
+	require.NoError(t, err)
+	atx := newAtx(t, sig)
+	atx.AtxBlob.Blob = []byte("blob1")
+	atx.AtxBlob.Version = 0
+
+	require.NoError(t, atxs.Add(db, atx))
+
+	var blob sql.Blob
+	version, err := atxs.LoadBlob(context.Background(), db, atx.ID().Bytes(), &blob)
+	require.NoError(t, err)
+	require.Equal(t, types.AtxV1, version)
+	require.Equal(t, atx.AtxBlob.Blob, blob.Bytes)
+}
+
 func TestGetBlobCached(t *testing.T) {
 	db := sql.InMemory(sql.WithQueryCache(true))
 	ctx := context.Background()

sql/migrations/state/0018_atx_blob_version.sql

@@ -1,4 +1,3 @@
 -- Add version column to make it easier to decode the blob
 -- to the right version of ATX.
 ALTER TABLE atx_blobs ADD COLUMN version INTEGER;
-UPDATE atx_blobs SET version = 1;