diff --git a/include/l0_sampling/sketch.h b/include/l0_sampling/sketch.h
index fe5cc863..81bc5701 100644
--- a/include/l0_sampling/sketch.h
+++ b/include/l0_sampling/sketch.h
@@ -9,6 +9,7 @@
 #include <mutex>
 #include <utility>
 #include <vector>
+#include <unordered_set>
 
 #include "../types.h"
 #include "../util.h"
@@ -130,7 +131,7 @@ class Sketch {
    * Function to query all columns within a sketch to return 1 or more non-zero indices
    * @return   A pair with the result indices and a code indicating the type of result.
    */
-  std::pair<std::vector<vec_t>, SampleSketchRet> exhaustive_query();
+  std::pair<std::unordered_set<vec_t>, SampleSketchRet> exhaustive_query();
 
   inline uint64_t get_seed() const { return seed; }
   inline size_t column_seed(size_t column_idx) const { return seed + column_idx*5; }
diff --git a/include/supernode.h b/include/supernode.h
index 788bf4ac..800ee49c 100644
--- a/include/supernode.h
+++ b/include/supernode.h
@@ -152,7 +152,7 @@ class Supernode {
    *            if one exists. Additionally, returns a code represnting the sample
    *            result (good, zero, or fail)
    */
-  std::pair<std::vector<Edge>, SampleSketchRet> exhaustive_sample();
+  std::pair<std::unordered_set<Edge>, SampleSketchRet> exhaustive_sample();
 
   /**
    * In-place merge function. Guaranteed to update the caller Supernode.
diff --git a/include/types.h b/include/types.h
index e65f572d..dc7cddf3 100644
--- a/include/types.h
+++ b/include/types.h
@@ -24,7 +24,19 @@ struct Edge {
       return dst < oth.dst;
     return src < oth.src;
   }
+  bool operator== (const Edge&oth) const {
+    return src == oth.src && dst == oth.dst;
+  }
 };
+namespace std {
+  template <>
+  struct hash<Edge> {
+    auto operator()(const Edge&edge) const -> size_t {
+      std::hash<size_t> h;
+      return h(edge.dst) + (31 * h(edge.src));
+    }
+  };
+}
 
 struct GraphUpdate {
   Edge edge;
diff --git a/src/l0_sampling/sketch.cpp b/src/l0_sampling/sketch.cpp
index 407f4009..e1c74d14 100644
--- a/src/l0_sampling/sketch.cpp
+++ b/src/l0_sampling/sketch.cpp
@@ -115,17 +115,17 @@ std::pair<vec_t, SampleSketchRet> Sketch::query() {
   return {0, FAIL};
 }
 
-std::pair<std::vector<vec_t>, SampleSketchRet> Sketch::exhaustive_query() {
+std::pair<std::unordered_set<vec_t>, SampleSketchRet> Sketch::exhaustive_query() {
   unlikely_if (already_queried)
     throw MultipleQueryException();
-  std::vector<vec_t> ret;
+  std::unordered_set<vec_t> ret;
 
   unlikely_if (bucket_a[num_elems - 1] == 0 && bucket_c[num_elems - 1] == 0)
     return {ret, ZERO}; // the "first" bucket is deterministic so if zero then no edges to return
 
   unlikely_if (
   Bucket_Boruvka::is_good(bucket_a[num_elems - 1], bucket_c[num_elems - 1], checksum_seed())) {
-    ret.push_back(bucket_a[num_elems - 1]);
+    ret.insert(bucket_a[num_elems - 1]);
     return {ret, GOOD};
   }
   for (unsigned i = 0; i < num_columns; ++i) {
@@ -133,8 +133,7 @@ std::pair<std::vector<vec_t>, SampleSketchRet> Sketch::exhaustive_query() {
       unsigned bucket_id = i * num_guesses + j;
       unlikely_if (
       Bucket_Boruvka::is_good(bucket_a[bucket_id], bucket_c[bucket_id], checksum_seed())) {
-        ret.push_back(bucket_a[bucket_id]);
-        update(bucket_a[bucket_id]);
+        ret.insert(bucket_a[bucket_id]);
       }
     }
   }
diff --git a/src/supernode.cpp b/src/supernode.cpp
index d9f45057..13e96fb4 100644
--- a/src/supernode.cpp
+++ b/src/supernode.cpp
@@ -93,13 +93,14 @@ std::pair<Edge, SampleSketchRet> Supernode::sample() {
   return {inv_concat_pairing_fn(non_zero), ret_code};
 }
 
-std::pair<std::vector<Edge>, SampleSketchRet> Supernode::exhaustive_sample() {
+std::pair<std::unordered_set<Edge>, SampleSketchRet> Supernode::exhaustive_sample() {
   if (out_of_queries()) throw OutOfQueriesException();
 
-  std::pair<std::vector<vec_t>, SampleSketchRet> query_ret = get_sketch(sample_idx++)->exhaustive_query();
-  std::vector<Edge> edges(query_ret.first.size());
-  for (size_t i = 0; i < edges.size(); i++)
-    edges[i] = inv_concat_pairing_fn(query_ret.first[i]);
+  std::pair<std::unordered_set<vec_t>, SampleSketchRet> query_ret = get_sketch(sample_idx++)->exhaustive_query();
+  std::unordered_set<Edge> edges(query_ret.first.size());
+  for (const auto &query_item: query_ret.first) {
+    edges.insert(inv_concat_pairing_fn(query_item));
+  }
 
   SampleSketchRet ret_code = query_ret.second;
   return {edges, ret_code};
diff --git a/test/sketch_test.cpp b/test/sketch_test.cpp
index 13de1e0f..f7b6fdab 100644
--- a/test/sketch_test.cpp
+++ b/test/sketch_test.cpp
@@ -358,7 +358,7 @@ TEST(SketchTestSuite, TestExhaustiveQuery) {
     sketch->update(9);
     sketch->update(10);
 
-    std::pair<std::vector<vec_t>, SampleSketchRet> query_ret = sketch->exhaustive_query();
+    std::pair<std::unordered_set<vec_t>, SampleSketchRet> query_ret = sketch->exhaustive_query();
     if (query_ret.second != GOOD) {
       ASSERT_EQ(query_ret.first.size(), 0) << query_ret.second;
     }
diff --git a/test/supernode_test.cpp b/test/supernode_test.cpp
index 1bdc25ce..35959ff6 100644
--- a/test/supernode_test.cpp
+++ b/test/supernode_test.cpp
@@ -288,7 +288,7 @@ TEST_F(SupernodeTestSuite, ExhaustiveSample) {
 
     // do 4 samples
     for (size_t i = 0; i < 4; i++) {
-      std::pair<std::vector<Edge>, SampleSketchRet> query_ret = s_node->exhaustive_sample();
+      std::pair<std::unordered_set<Edge>, SampleSketchRet> query_ret = s_node->exhaustive_sample();
       if (query_ret.second != GOOD) {
         ASSERT_EQ(query_ret.first.size(), 0);
       }