Do not store subfile signatures for very short blocks.

Don't bother to store subfile signatures for very short files, since it is
probably not worth the effort: we're probably best off just storing a new
copy of the data if it changes anyway.

For now, we used a fixed and non-scientific threshold of 16 kB as the
minimum size before we'll save subfile signatures.  However, short blocks
that are created to store any new chunks needed for a subfile incremental
are always indexed (since we are likely to want to use the same chunks
again in the next backup).

diff --git a/subfile.cc b/subfile.cc
index f365c4b..4e13005 100644 (file)
--- a/subfile.cc
+++ b/subfile.cc
@@ -264,7 +264,8 @@ list<ObjectReference> Subfile::create_incremental(TarSegmentStore *tss,
         o->write(tss);
         ObjectReference ref = o->get_ref();
         db->StoreObject(ref, block_csum, analyzed_len, block_age);
-        store_block_signatures(ref, new_block_summary);
+        if (analyzed_len >= 16384)
+            store_block_signatures(ref, new_block_summary);
         refs.push_back(ref);
         delete o;
         return refs;