diff --git a/crates/table/src/blob_store.rs b/crates/table/src/blob_store.rs
index 6155d884b5d..2f3b286ab44 100644
--- a/crates/table/src/blob_store.rs
+++ b/crates/table/src/blob_store.rs
@@ -12,6 +12,7 @@
 //!   It is not optimize and is mainly intended for testing purposes.
 
 use blake3::hash;
+use core::mem;
 use spacetimedb_data_structures::map::{hash_map::Entry, HashMap};
 use spacetimedb_lib::{de::Deserialize, ser::Serialize};
 use spacetimedb_memory_usage::MemoryUsage;
@@ -233,15 +234,20 @@ impl BlobStore for HashMapBlobStore {
     }
 }
 
-#[cfg(test)]
 impl HashMapBlobStore {
-    /// Returns an iterator over the (hash, usage count, blob bytes) triple.
-    fn iter(&self) -> impl Iterator<Item = (&BlobHash, usize, &[u8])> + '_ {
-        self.map.iter().map(|(hash, obj)| (hash, obj.uses, &*obj.blob))
+    /// Merge `src_bs` into `self`.
+    pub fn merge_from(&mut self, src_bs: Self) {
+        for (hash, mut obj) in src_bs.map {
+            let uses = mem::take(&mut obj.uses);
+            self.map.entry(hash).or_insert(obj).uses += uses;
+        }
     }
+}
 
+#[cfg(test)]
+impl HashMapBlobStore {
     /// Returns a map relating blob hashes to the usage count in this blob store.
     pub fn usage_counter(&self) -> HashMap<BlobHash, usize> {
-        self.iter().map(|(hash, uses, _)| (*hash, uses)).collect()
+        self.iter_blobs().map(|(hash, uses, _)| (*hash, uses)).collect()
     }
 }