diff --git a/db/src/db.rs b/db/src/db.rs
index f43ef6a8..170e4e3b 100644
--- a/db/src/db.rs
+++ b/db/src/db.rs
@@ -2310,7 +2310,6 @@ mod tests {
     }
 
     // TODO
-    /*
     #[test]
     fn test_cardinality_one_violation_new_entity() {
         let mut conn = TestConn::default();
@@ -2344,5 +2343,4 @@ mod tests {
                             [998 :test/one 124 ?tx true]
                             [?tx :db/txInstant ?ms ?tx true]]"#);
     }
-    */
 }
diff --git a/db/src/tx.rs b/db/src/tx.rs
index 190a9fab..be880e0d 100644
--- a/db/src/tx.rs
+++ b/db/src/tx.rs
@@ -164,6 +164,7 @@ impl<'conn, 'a> Tx<'conn, 'a> {
     /// which [a v] pairs do upsert to entids, and map each tempid that upserts to the upserted
     /// entid.  The keys of the resulting map are exactly those tempids that upserted.
     pub fn resolve_temp_id_avs<'b>(&self, temp_id_avs: &'b [(TempIdHandle, AVPair)]) -> Result<TempIdMap> {
+        println!("resolve_temp_id_avs: {:?}", temp_id_avs);
         if temp_id_avs.is_empty() {
             return Ok(TempIdMap::default());
         }
@@ -191,6 +192,7 @@ impl<'conn, 'a> Tx<'conn, 'a> {
             }
         }
 
+        println!("=> {:?}", temp_id_map);
         Ok((temp_id_map))
     }
 
@@ -485,6 +487,7 @@ impl<'conn, 'a> Tx<'conn, 'a> {
                 },
             }
         };
+        println!("TERMS: {:?}", terms);
         Ok((terms, in_process.temp_ids, in_process.lookup_refs))
     }
 
@@ -493,15 +496,46 @@ impl<'conn, 'a> Tx<'conn, 'a> {
     ///
     /// The `Term` instances produced share interned TempId handles and have no LookupRef references.
     fn resolve_lookup_refs<I>(&self, lookup_ref_map: &AVMap, terms: I) -> Result<Vec<TermWithTempIds>> where I: IntoIterator<Item=TermWithTempIdsAndLookupRefs> {
-        terms.into_iter().map(|term: TermWithTempIdsAndLookupRefs| -> Result<TermWithTempIds> {
+        println!("\nLookup ref map: {:?}", lookup_ref_map);
+
+        let mut equivalences: ::std::collections::HashMap<(Entid, TypedValue), BTreeSet<TempIdHandle>> = Default::default();
+
+        let res = terms.into_iter().map(|term: TermWithTempIdsAndLookupRefs| -> Result<TermWithTempIds> {
+            println!("\nResolving lookup refs: {:?}", term);
             match term {
                 Term::AddOrRetract(op, e, a, v) => {
                     let e = replace_lookup_ref(&lookup_ref_map, e, |x| KnownEntid(x))?;
                     let v = replace_lookup_ref(&lookup_ref_map, v, |x| TypedValue::Ref(x))?;
+
+                    // It's possible here that we'll encounter two lookup refs that are the same,
+                    // but have different tempids. We want these to collide to avoid problems in
+                    // the storage layer.
+                    if let (OpType::Add, &Either::Right(ref tempid), &Either::Left(ref vv)) = (op, &e, &v) {
+                         let pair: AVPair = (a, vv.clone());
+
+                         println!("TempID {:?} is identified by {:?}", tempid, pair);
+
+                        equivalences.entry(pair)
+                                    .or_insert(Default::default())
+                                    .insert(tempid.clone());
+                    }
                     Ok(Term::AddOrRetract(op, e, a, v))
                 },
             }
-        }).collect::<Result<Vec<_>>>()
+        }).collect::<Result<Vec<_>>>();
+
+        // Now invert the equivalences index: we wish to go from the entire set of tempids to
+        // a subset of canonical tempids.
+        let mut tempids: ::std::collections::HashMap<TempIdHandle, TempIdHandle> = Default::default();
+        for (_, set) in equivalences.into_iter().filter(|&(_, ref v)| v.len() > 1) {
+            let mut all = set.into_iter();
+            let winner = all.next().unwrap();    // Length check above.
+            for t in all {
+                tempids.insert(t, winner.clone());
+            }
+        }
+        println!("Found equivalences: {:?}", &tempids);
+        res
     }
 
     /// Transact the given `entities` against the store.
@@ -521,6 +555,7 @@ impl<'conn, 'a> Tx<'conn, 'a> {
 
         let terms_with_temp_ids = self.resolve_lookup_refs(&lookup_ref_map, terms_with_temp_ids_and_lookup_refs)?;
 
+println!("Terms with temp IDs: {:?}", terms_with_temp_ids);
         // Pipeline stage 3: upsert tempids -> terms without tempids or lookup refs.
         // Now we can collect upsert populations.
         let (mut generation, inert_terms) = Generation::from(terms_with_temp_ids, &self.schema)?;
@@ -551,6 +586,8 @@ impl<'conn, 'a> Tx<'conn, 'a> {
         // Allocate entids for tempids that didn't upsert.  BTreeSet rather than HashSet so this is deterministic.
         let unresolved_temp_ids: BTreeSet<TempIdHandle> = generation.temp_ids_in_allocations();
 
+println!("\nUNRESOLVED: \n>> {:?}\n>> {:?}\n", unresolved_temp_ids, &generation.temp_id_avs()[..]);
+
         // TODO: track partitions for temporary IDs.
         let entids = self.partition_map.allocate_entids(":db.part/user", unresolved_temp_ids.len());
 
@@ -587,6 +624,7 @@ impl<'conn, 'a> Tx<'conn, 'a> {
         let final_terms: Vec<TermWithoutTempIds> = [final_populations.resolved,
                                                     final_populations.allocated,
                                                     inert_terms.into_iter().map(|term| term.unwrap()).collect()].concat();
+println!("Final terms: {:?}", final_terms);
 
         { // TODO: Don't use this block to scope borrowing the schema; instead, extract a helper function.
 
@@ -636,6 +674,7 @@ impl<'conn, 'a> Tx<'conn, 'a> {
                           TypedValue::Instant(self.tx_instant),
                           true));
 
+println!("non_fts_one: {:?}", non_fts_one);
         if !non_fts_one.is_empty() {
             self.store.insert_non_fts_searches(&non_fts_one[..], db::SearchType::Inexact)?;
         }
diff --git a/db/src/upsert_resolution.rs b/db/src/upsert_resolution.rs
index 3c74562f..aae27540 100644
--- a/db/src/upsert_resolution.rs
+++ b/db/src/upsert_resolution.rs
@@ -144,6 +144,7 @@ impl Generation {
     ///
     /// TODO: Considering doing this in place; the function already consumes `self`.
     pub fn evolve_one_step(self, temp_id_map: &TempIdMap) -> Generation {
+        println!("EVOLVE ONE STEP: {:?}\n", temp_id_map);
         let mut next = Generation::default();
 
         for UpsertE(t, a, v) in self.upserts_e {