diff --git a/db/src/db.rs b/db/src/db.rs
index e52a7384..dfffe9f9 100644
--- a/db/src/db.rs
+++ b/db/src/db.rs
@@ -14,12 +14,10 @@ use failure::{
     ResultExt,
 };
 
-use std::borrow::Borrow;
 use std::collections::HashMap;
 use std::collections::hash_map::{
     Entry,
 };
-use std::fmt::Display;
 use std::iter::{once, repeat};
 use std::ops::Range;
 use std::path::Path;
@@ -1080,20 +1078,14 @@ SELECT EXISTS
     Ok(())
 }
 
-pub trait PartitionMapping {
-    fn allocate_entid<S: ?Sized + Ord + Display>(&mut self, partition: &S) -> i64 where String: Borrow<S>;
-    fn allocate_entids<S: ?Sized + Ord + Display>(&mut self, partition: &S, n: usize) -> Range<i64> where String: Borrow<S>;
-    fn contains_entid(&self, entid: Entid) -> bool;
-}
-
-impl PartitionMapping for PartitionMap {
+impl PartitionMap {
     /// Allocate a single fresh entid in the given `partition`.
-    fn allocate_entid<S: ?Sized + Ord + Display>(&mut self, partition: &S) -> i64 where String: Borrow<S> {
+    pub(crate) fn allocate_entid(&mut self, partition: &str) -> i64 {
         self.allocate_entids(partition, 1).start
     }
 
     /// Allocate `n` fresh entids in the given `partition`.
-    fn allocate_entids<S: ?Sized + Ord + Display>(&mut self, partition: &S, n: usize) -> Range<i64> where String: Borrow<S> {
+    pub(crate) fn allocate_entids(&mut self, partition: &str, n: usize) -> Range<i64> {
         match self.get_mut(partition) {
             Some(partition) => {
                 let idx = partition.index;
@@ -1105,7 +1097,7 @@ impl PartitionMapping for PartitionMap {
         }
     }
 
-    fn contains_entid(&self, entid: Entid) -> bool {
+    pub(crate) fn contains_entid(&self, entid: Entid) -> bool {
         self.values().any(|partition| partition.contains_entid(entid))
     }
 }
@@ -1114,6 +1106,10 @@ impl PartitionMapping for PartitionMap {
 mod tests {
     extern crate env_logger;
 
+    use std::borrow::{
+        Borrow,
+    };
+
     use super::*;
     use debug::{TestConn,tempids};
     use edn::{
diff --git a/db/src/tx.rs b/db/src/tx.rs
index 4179fa24..85010f4b 100644
--- a/db/src/tx.rs
+++ b/db/src/tx.rs
@@ -60,7 +60,6 @@ use std::iter::{
 use db;
 use db::{
     MentatStoring,
-    PartitionMapping,
 };
 use edn::{
     InternSet,
diff --git a/db/src/types.rs b/db/src/types.rs
index 8d951e54..9416dcbe 100644
--- a/db/src/types.rs
+++ b/db/src/types.rs
@@ -10,10 +10,17 @@
 
 #![allow(dead_code)]
 
-use std::collections::HashMap;
 use std::collections::{
     BTreeMap,
     BTreeSet,
+    HashMap,
+};
+use std::iter::{
+    FromIterator,
+};
+use std::ops::{
+    Deref,
+    DerefMut,
 };
 
 extern crate mentat_core;
@@ -37,7 +44,7 @@ use edn::entities::{
 use errors;
 
 /// Represents one partition of the entid space.
-#[derive(Clone,Debug,Eq,Hash,Ord,PartialOrd,PartialEq)]
+#[derive(Clone, Debug, Eq, Hash, Ord, PartialOrd, PartialEq)]
 #[cfg_attr(feature = "syncable", derive(Serialize,Deserialize))]
 pub struct Partition {
     /// The first entid in the partition.
@@ -66,7 +73,28 @@ impl Partition {
 }
 
 /// Map partition names to `Partition` instances.
-pub type PartitionMap = BTreeMap<String, Partition>;
+#[derive(Clone, Debug, Default, Eq, Hash, Ord, PartialOrd, PartialEq)]
+pub struct PartitionMap(BTreeMap<String, Partition>);
+
+impl Deref for PartitionMap {
+    type Target = BTreeMap<String, Partition>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for PartitionMap {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl FromIterator<(String, Partition)> for PartitionMap {
+    fn from_iter<T: IntoIterator<Item=(String, Partition)>>(iter: T) -> Self {
+        PartitionMap(iter.into_iter().collect())
+    }
+}
 
 /// Represents the metadata required to query from, or apply transactions to, a Mentat store.
 ///