fix in-mem deletion

cozo-core/src/query/stored.rs

@@ -68,9 +68,8 @@ impl<'a> SessionTx<'a> {
                     })?;
                     to_clear.extend(cleanups);
                 }
-            }
-            if let Ok(c) = self.destroy_relation(&meta.name) {
-                to_clear.push(c);
+
+                to_clear.push(self.destroy_relation(&meta.name)?);
             }
         }
         let mut relation_store = if op == RelationOp::Replace || op == RelationOp::Create {

cozo-core/src/storage/mem.rs

@@ -116,7 +116,7 @@ impl<'s> StoreTx<'s> for MemTx<'s> {
                 bail!("write in read transaction")
             }
             MemTx::Writer(_, cache) => {
-                cache.remove(key);
+                cache.insert(key.to_vec(), None);
                 Ok(())
             }
         }