diff --git a/contracts/okp4-cognitarium/src/contract.rs b/contracts/okp4-cognitarium/src/contract.rs
index 0ac156bb..1cf22059 100644
--- a/contracts/okp4-cognitarium/src/contract.rs
+++ b/contracts/okp4-cognitarium/src/contract.rs
@@ -51,9 +51,9 @@ pub mod execute {
     use super::*;
     use crate::msg::{DataFormat, Prefix, SelectItem, TriplePattern, WhereClause};
     use crate::querier::{PlanBuilder, QueryEngine};
-    use crate::rdf::{Atom, TripleReader};
+    use crate::rdf::TripleReader;
     use crate::storer::StoreEngine;
-    use std::collections::HashSet;
+    use std::collections::{BTreeMap, HashSet};
     use std::io::BufReader;
 
     pub fn verify_owner(deps: &DepsMut, info: &MessageInfo) -> Result<(), ContractError> {
@@ -103,12 +103,16 @@ pub mod execute {
             .collect();
 
         let response = QueryEngine::new(deps.storage).select(plan, variables)?;
-        let atoms: Vec<Atom> = response
-            .results
-            .bindings
-            .iter()
-            .flat_map(|row| delete.iter().map(|pattern| pattern.resolve(row, &prefixes)))
-            .collect::<Result<Vec<_>, _>>()?;
+        let atoms: Vec<Atom> = if response.results.bindings.is_empty() {
+            vec![]
+        } else {
+            response
+                .results
+                .bindings
+                .iter()
+                .flat_map(|row| delete.iter().map(|pattern| pattern.resolve(row, &prefixes)))
+                .collect::<Result<Vec<_>, _>>()?
+        };
 
         let mut storer = StoreEngine::new(deps.storage)?;
         let count = storer.delete_all(&atoms)?;
diff --git a/contracts/okp4-cognitarium/src/storer/engine.rs b/contracts/okp4-cognitarium/src/storer/engine.rs
index 5c7a0736..64cde7f8 100644
--- a/contracts/okp4-cognitarium/src/storer/engine.rs
+++ b/contracts/okp4-cognitarium/src/storer/engine.rs
@@ -115,6 +115,8 @@ impl<'a> StoreEngine<'a> {
             .map_err(ContractError::Std)
     }
 
+    /// Flushes the store to the storage.
+    /// Returns the number of triples added or removed (absolute value).
     pub fn finish(&mut self) -> Result<Uint128, ContractError> {
         STORE.save(self.storage, &self.store)?;
         NAMESPACE_KEY_INCREMENT.save(self.storage, &self.ns_key_inc_offset)?;
@@ -122,7 +124,11 @@ impl<'a> StoreEngine<'a> {
             namespaces().save(self.storage, entry.0.to_string(), entry.1)?;
         }
 
-        Ok(self.store.stat.triple_count - self.initial_triple_count)
+        if self.store.stat.triple_count > self.initial_triple_count {
+            Ok(self.store.stat.triple_count - self.initial_triple_count)
+        } else {
+            Ok(self.initial_triple_count - self.store.stat.triple_count)
+        }
     }
 
     fn resolve_namespace_key(&mut self, ns_str: String) -> StdResult<u128> {