diff --git a/src/datomish/db.cljc b/src/datomish/db.cljc
index 0e5e49c9..634ec603 100644
--- a/src/datomish/db.cljc
+++ b/src/datomish/db.cljc
@@ -82,16 +82,15 @@
     [db eid]
     "Returns the keyword associated with an id, or the key itself if passed.")
 
-  (current-tx
-    [db]
-    "TODO: document this interface.")
-
   (in-transaction!
     [db chan-fn]
     "Evaluate the given pair-chan `chan-fn` in an exclusive transaction. If it returns non-nil,
     commit the transaction; otherwise, rollback the transaction.  Returns a pair-chan resolving to
     the pair-chan returned by `chan-fn`.")
 
+  (<bootstrapped? [db]
+    "Return true if this database has no transactions yet committed.")
+
   (<ea [db e a]
     "Search for datoms using the EAVT index.")
 
@@ -114,9 +113,10 @@
     [db fragment merge]
     "Apply added schema fragment to the store, using `merge` as a `merge-with` function.")
 
-  (<advance-tx
-    [db]
-    "TODO: document this interface."))
+  (<next-eid
+    [db id-literal]
+    "Return a unique integer for the given id-literal, accounting for the literal's partition.  The
+    returned integer should never be returned again."))
 
 (defn db? [x]
   (and (satisfies? IDB x)
@@ -146,7 +146,6 @@
           ]
       rowid)))
 
-
 (defn datoms-attribute-transform
   [db x]
   {:pre [(db? db)]}
@@ -168,11 +167,14 @@
      :table-alias source/gensym-table-alias
      :make-constraints nil}))
 
-(defrecord DB [sqlite-connection schema entids ident-map current-tx]
+(defrecord DB [sqlite-connection schema ident-map]
   ;; ident-map maps between keyword idents and integer entids.  The set of idents and entids is
   ;; disjoint, so we represent both directions of the mapping in the same map for simplicity.  Also
   ;; for simplicity, we assume that an entid has at most one associated ident, and vice-versa.  See
   ;; http://docs.datomic.com/identity.html#idents.
+
+  ;; TODO: cache parts.  parts looks like {:db.part/db {:start 0 :current 10}}.  It maps between
+  ;; keyword ident part names and integer ranges.
   IDB
   (query-context [db] (context/->Context (datoms-source db) nil nil))
 
@@ -188,14 +190,20 @@
       (get (.-ident-map db) eid eid)
       eid))
 
-  (current-tx
-    [db]
-    (inc (:current-tx db)))
-
   (in-transaction! [db chan-fn]
     (s/in-transaction!
       (:sqlite-connection db) chan-fn))
 
+  (<bootstrapped? [db]
+    (go-pair
+      (->
+        (:sqlite-connection db)
+        (s/all-rows ["SELECT EXISTS(SELECT 1 FROM transactions LIMIT 1) AS bootstrapped"])
+        (<?)
+        (first)
+        (:bootstrapped)
+        (not= 0))))
+
   ;; TODO: use q for searching?  Have q use this for searching for a single pattern?
   (<ea [db e a]
     (go-pair
@@ -272,15 +280,21 @@
                       ["DELETE FROM datoms WHERE (e = ? AND a = ? AND value_type_tag = ? AND v = ?)" e a tag v])))))))
       db))
 
-  (<advance-tx [db]
+  (<next-eid [db tempid]
+    {:pre [(id-literal? tempid)]}
+    {:post [ds/entid?]}
     (go-pair
-      (let [exec (partial s/execute! (:sqlite-connection db))]
-        ;; (let [ret (<? (exec
-        ;;                 ;; TODO: be more clever about UPDATE OR ...?
-        ;;                 ["UPDATE metadata SET current_tx = ? WHERE current_tx = ?" (inc (:current-tx db)) (:current-tx db)]))]
+      ;; TODO: keep all of these eid allocations in the transaction report and apply them at the end
+      ;; of the transaction.
+      (let [exec (partial s/execute! (:sqlite-connection db))
+            part (entid db (:part tempid))]
+        (when-not (ds/entid? part) ;; TODO: cache parts materialized view.
+          (raise "Cannot allocate entid for id-literal " tempid " because part " (:part tempid) " is not known"
+                 {:error :db/bad-part
+                  :part (:part tempid)}))
 
-        ;; TODO: handle exclusion across transactions here.
-        (update db :current-tx inc))))
+        (<? (exec ["UPDATE parts SET idx = idx + 1 WHERE part = ?" part]))
+        (:eid (first (<? (s/all-rows (:sqlite-connection db) ["SELECT (start + idx) AS eid FROM parts WHERE part = ?" part])))))))
 
   (<apply-db-ident-assertions [db added-idents merge]
     (go-pair
@@ -321,7 +335,7 @@
 (defn with-ident [db ident entid]
   (update db :ident-map #(assoc % ident entid, entid ident)))
 
-(defn db [sqlite-connection idents schema current-tx]
+(defn db [sqlite-connection idents schema]
   {:pre [(map? idents)
          (every? keyword? (keys idents))
          (map? schema)
@@ -333,7 +347,8 @@
        :ident-map         ident-map
        :symbolic-schema   schema
        :schema            entid-schema
-       :current-tx        current-tx})))
+       ;; TODO :parts
+       })))
 
 ;; TODO: factor this into the overall design.
 (defn <?run
diff --git a/src/datomish/db_factory.cljc b/src/datomish/db_factory.cljc
index 225d9f5d..2c8b7131 100644
--- a/src/datomish/db_factory.cljc
+++ b/src/datomish/db_factory.cljc
@@ -23,9 +23,6 @@
      (:import
       [datomish.datom Datom])))
 
-;; TODO: implement support for DB parts?
-(def tx0 0x2000000)
-
 (defn <idents [sqlite-connection]
   "Read the ident map materialized view from the given SQLite store.
   Returns a map (keyword ident) -> (integer entid), like {:db/ident 0}."
@@ -37,14 +34,6 @@
                      (s/all-rows sqlite-connection)))]
       (into {} (map (fn [row] [(sqlite-schema/<-SQLite :db.type/keyword (:ident row)) (:entid row)])) rows))))
 
-(defn <current-tx [sqlite-connection]
-  "Find the largest tx written to the SQLite store.
-  Returns an integer, -1 if no transactions have been written yet."
-
-  (go-pair
-    (let [rows (<? (s/all-rows sqlite-connection ["SELECT COALESCE(MAX(tx), -1) AS current_tx FROM transactions"]))]
-      (:current_tx (first rows)))))
-
 (defn <symbolic-schema [sqlite-connection]
   "Read the schema map materialized view from the given SQLite store.
   Returns a map (keyword ident) -> (map (keyword attribute -> keyword value)), like
@@ -83,10 +72,9 @@
     (when-not (= sqlite-schema/current-version (<? (sqlite-schema/<ensure-current-version sqlite-connection)))
       (raise "Could not ensure current SQLite schema version."))
 
-    (let [current-tx   (<? (<current-tx sqlite-connection))
-          bootstrapped (>= current-tx 0)
-          current-tx   (max current-tx tx0)]
-      (when-not bootstrapped
+    (let [db            (db/db sqlite-connection bootstrap/idents bootstrap/symbolic-schema)
+          bootstrapped? (<? (db/<bootstrapped? db))]
+      (when-not bootstrapped?
         ;; We need to bootstrap the DB.
         (let [fail-alter-ident (fn [old new] (if-not (= old new)
                                                (raise "Altering idents is not yet supported, got " new " altering existing ident " old
@@ -96,29 +84,40 @@
                                                (raise "Altering schema attributes is not yet supported, got " new " altering existing schema attribute " old
                                                       {:error :schema/alter-schema :old old :new new})
                                                new))]
-          (-> (db/db sqlite-connection bootstrap/idents bootstrap/symbolic-schema current-tx)
-              ;; We use <with-internal rather than <transact! to apply the bootstrap transaction
-              ;; data but to not follow the regular schema application process.  We can't apply the
-              ;; schema changes, since the applied datoms would conflict with the bootstrapping
-              ;; idents and schema.  (The bootstrapping idents and schema are required to be able to
-              ;; write to the database conveniently; without them, we'd have to manually write
-              ;; datoms to the store.  It's feasible but awkward.)  After bootstrapping, we read
-              ;; back the idents and schema, just like when we re-open.
-              (transact/<with-internal (bootstrap/tx-data) fail-alter-ident fail-alter-attr)
-              (<?))))
+          (do
+            (let [exec (partial s/execute! (:sqlite-connection db))]
+              ;; TODO: allow inserting new parts.
+              ;; TODO: think more carefully about allocating new parts and bitmasking part ranges.
+              (<? (exec
+                    ["INSERT INTO parts VALUES (?, ?, ?)" (db/entid db :db.part/db) 0x0 (inc (apply max (vals bootstrap/idents)))]))
+              (<? (exec
+                    ["INSERT INTO parts VALUES (?, ?, ?)" (db/entid db :db.part/user) 0x10000 0]))
+              (<? (exec
+                    ["INSERT INTO parts VALUES (?, ?, ?)" (db/entid db :db.part/tx) 0x10000000 0])))
+            (-> db
+                ;; We use <with-internal rather than <transact! to apply the bootstrap transaction
+                ;; data but to not follow the regular schema application process.  We can't apply the
+                ;; schema changes, since the applied datoms would conflict with the bootstrapping
+                ;; idents and schema.  (The bootstrapping idents and schema are required to be able to
+                ;; write to the database conveniently; without them, we'd have to manually write
+                ;; datoms to the store.  It's feasible but awkward.)  After bootstrapping, we read
+                ;; back the idents and schema, just like when we re-open.
+                (transact/<with-internal (bootstrap/tx-data) fail-alter-ident fail-alter-attr)
+                (<?)))))
 
       ;; We just bootstrapped, or we are returning to an already bootstrapped DB.
       (let [idents          (<? (<idents sqlite-connection))
             symbolic-schema (<? (<symbolic-schema sqlite-connection))]
-        (when-not bootstrapped
+        (when-not bootstrapped?
+          ;; TODO: parts.
           (when (not (= idents bootstrap/idents))
             (raise "After bootstrapping database, expected new materialized idents and old bootstrapped idents to be identical"
                    {:error :bootstrap/bad-idents,
-                    :new idents :old bootstrap/idents
+                    :new   idents :old bootstrap/idents
                     }))
           (when (not (= symbolic-schema bootstrap/symbolic-schema))
             (raise "After bootstrapping database, expected new materialized symbolic schema and old bootstrapped symbolic schema to be identical"
                    {:error :bootstrap/bad-symbolic-schema,
-                    :new symbolic-schema :old bootstrap/symbolic-schema
+                    :new   symbolic-schema :old bootstrap/symbolic-schema
                     })))
-        (db/db sqlite-connection idents symbolic-schema (inc current-tx))))))
+        (db/db sqlite-connection idents symbolic-schema)))))
diff --git a/src/datomish/schema.cljc b/src/datomish/schema.cljc
index 8e599d9a..7c4ad286 100644
--- a/src/datomish/schema.cljc
+++ b/src/datomish/schema.cljc
@@ -9,6 +9,9 @@
    [datomish.sqlite-schema :as sqlite-schema]
    [datomish.util :as util #?(:cljs :refer-macros :clj :refer) [raise]]))
 
+(defn entid? [x]
+  (and (integer? x) (pos? x)))
+
 (defprotocol ISchema
   (attrs-by
     [schema property]
@@ -97,7 +100,7 @@
                      :value v}))))
 
 (def value-type-map
-  {:db.type/ref     { :valid? #(and (integer? %) (pos? %)) }
+  {:db.type/ref     { :valid? entid? }
    :db.type/keyword { :valid? keyword? }
    :db.type/string  { :valid? string? }
    :db.type/boolean { :valid? #?(:clj #(instance? Boolean %) :cljs #(= js/Boolean (type %))) }
diff --git a/src/datomish/sqlite_schema.cljc b/src/datomish/sqlite_schema.cljc
index a0936041..768b96b9 100644
--- a/src/datomish/sqlite_schema.cljc
+++ b/src/datomish/sqlite_schema.cljc
@@ -83,6 +83,7 @@
    ;; TODO: allow arbitrary schema values (true/false) and tag the resulting values.
    "CREATE TABLE schema (ident TEXT NOT NULL, attr TEXT NOT NULL, value TEXT NOT NULL, FOREIGN KEY (ident) REFERENCES idents (ident))"
    "CREATE INDEX idx_schema_unique ON schema (ident, attr, value)"
+   "CREATE TABLE parts (part INTEGER NOT NULL PRIMARY KEY, start INTEGER NOT NULL, idx INTEGER NOT NULL)"
    ])
 
 (defn <create-current-version
diff --git a/src/datomish/transact.cljc b/src/datomish/transact.cljc
index 11c764c0..b9dc82dc 100644
--- a/src/datomish/transact.cljc
+++ b/src/datomish/transact.cljc
@@ -56,7 +56,8 @@
 
 (defrecord TxReport [db-before ;; The DB before the transaction.
                      db-after  ;; The DB after the transaction.
-                     current-tx ;; The tx ID represented by the transaction in this report.
+                     tx        ;; The tx ID represented by the transaction in this report; refer :db/tx.
+                     txInstant ;; The timestamp instant when the the transaction was processed/committed in this report; refer :db/txInstant.
                      entities  ;; The set of entities (like [:db/add e a v tx]) processed.
                      tx-data   ;; The set of datoms applied to the database, like (Datom. e a v tx added).
                      tempids   ;; The map from id-literal -> numeric entid.
@@ -293,22 +294,22 @@
                   allocated-eid (get-in report [:tempids e])]
               (if (and upserted-eid allocated-eid (not= upserted-eid allocated-eid))
                 (<? (<retry-with-tempid db initial-report initial-entities e upserted-eid)) ;; TODO: not initial report, just the sorted entities here.
-                (let [eid (or upserted-eid allocated-eid (next-eid db))]
+                (let [eid (or upserted-eid allocated-eid (<? (db/<next-eid db e)))]
                   (recur (allocate-eid report e eid) (cons [op eid a v] entities)))))
 
             ;; Start allocating and retrying.  We try with e last, so as to eventually upsert it.
             (id-literal? v)
             ;; We can't fail with unbound literals here, since we could have multiple.
-            (let [eid (or (get-in report [:tempids v]) (next-eid db))]
+            (let [eid (or (get-in report [:tempids v]) (<? (db/<next-eid db e)))]
               (recur (allocate-eid report v eid) (cons [op e a eid] entities)))
 
             (id-literal? a)
             ;; TODO: should we even allow id-literal attributes?  Datomic fails in some cases here.
-            (let [eid (or (get-in report [:tempids a]) (next-eid db))]
+            (let [eid (or (get-in report [:tempids a]) (<? (db/<next-eid db e)))]
               (recur (allocate-eid report a eid) (cons [op e eid v] entities)))
 
             (id-literal? e)
-            (let [eid (or (get-in report [:tempids e]) (next-eid db))]
+            (let [eid (or (get-in report [:tempids e]) (<? (db/<next-eid db e)))]
               (recur (allocate-eid report e eid) (cons [op eid a v] entities)))
 
             true
@@ -516,7 +517,7 @@
                       ;; transaction ID and transaction timestamp directly from the report; Datomic
                       ;; makes this surprisingly difficult: one needs a :db.part/tx temporary and an
                       ;; explicit upsert of that temporary.
-                      :tx                (db/current-tx db)
+                      :tx                (<? (db/<next-eid db (id-literal :db.part/tx)))
                       :txInstant         (db/now db)
                       :entities          tx-data
                       :tx-data           []
@@ -542,9 +543,6 @@
                             (<?)
 
                             (db/<apply-db-install-assertions (:added-attributes report) merge-attr)
-                            (<?)
-
-                            (db/<advance-tx)
                             (<?))]
       (-> report
           (assoc-in [:db-after] db-after)))))
diff --git a/src/datomish/transact/bootstrap.cljc b/src/datomish/transact/bootstrap.cljc
index f5e72305..83dd4c8a 100644
--- a/src/datomish/transact/bootstrap.cljc
+++ b/src/datomish/transact/bootstrap.cljc
@@ -52,8 +52,8 @@
    :db/noHistory         13
    :db/add               14
    :db/retract           15
-   :db.part/tx           16
-   :db.part/user         17
+   :db.part/user         16
+   :db.part/tx           17
    :db/excise            18
    :db.excise/attrs      19
    :db.excise/beforeT    20
diff --git a/test/datomish/db_test.cljc b/test/datomish/db_test.cljc
index 6be310ff..29b8243a 100644
--- a/test/datomish/db_test.cljc
+++ b/test/datomish/db_test.cljc
@@ -73,47 +73,46 @@
       (<?)
       (mapv #(vector (:rowid %) (:text %))))))
 
-;; TODO: use reverse refs!
 (def test-schema
-  [{:db/id        (d/id-literal :test -1)
+  [{:db/id        (d/id-literal :db.part/user)
     :db/ident     :x
     :db/unique    :db.unique/identity
-    :db/valueType :db.type/long}
-   {:db/id :db.part/db :db.install/attribute (d/id-literal :test -1)}
-   {:db/id        (d/id-literal :test -2)
+    :db/valueType :db.type/long
+    :db.install/_attribute :db.part/db}
+   {:db/id        (d/id-literal :db.part/user)
     :db/ident     :name
     :db/unique    :db.unique/identity
-    :db/valueType :db.type/string}
-   {:db/id :db.part/db :db.install/attribute (d/id-literal :test -2)}
-   {:db/id          (d/id-literal :test -3)
+    :db/valueType :db.type/string
+    :db.install/_attribute :db.part/db}
+   {:db/id          (d/id-literal :db.part/user)
     :db/ident       :y
     :db/cardinality :db.cardinality/many
-    :db/valueType   :db.type/long}
-   {:db/id :db.part/db :db.install/attribute (d/id-literal :test -3)}
-   {:db/id          (d/id-literal :test -5)
+    :db/valueType   :db.type/long
+    :db.install/_attribute :db.part/db}
+   {:db/id          (d/id-literal :db.part/user)
     :db/ident       :aka
     :db/cardinality :db.cardinality/many
-    :db/valueType   :db.type/string}
-   {:db/id :db.part/db :db.install/attribute (d/id-literal :test -5)}
-   {:db/id        (d/id-literal :test -6)
+    :db/valueType   :db.type/string
+    :db.install/_attribute :db.part/db}
+   {:db/id        (d/id-literal :db.part/user)
     :db/ident     :age
-    :db/valueType :db.type/long}
-   {:db/id :db.part/db :db.install/attribute (d/id-literal :test -6)}
-   {:db/id        (d/id-literal :test -7)
+    :db/valueType :db.type/long
+    :db.install/_attribute :db.part/db}
+   {:db/id        (d/id-literal :db.part/user)
     :db/ident     :email
     :db/unique    :db.unique/identity
-    :db/valueType :db.type/string}
-   {:db/id :db.part/db :db.install/attribute (d/id-literal :test -7)}
-   {:db/id        (d/id-literal :test -8)
+    :db/valueType :db.type/string
+    :db.install/_attribute :db.part/db}
+   {:db/id        (d/id-literal :db.part/user)
     :db/ident     :spouse
     :db/unique    :db.unique/value
-    :db/valueType :db.type/string}
-   {:db/id :db.part/db :db.install/attribute (d/id-literal :test -8)}
-   {:db/id          (d/id-literal :test -9)
+    :db/valueType :db.type/string
+    :db.install/_attribute :db.part/db}
+   {:db/id          (d/id-literal :db.part/user)
     :db/ident       :friends
     :db/cardinality :db.cardinality/many
-    :db/valueType   :db.type/ref}
-   {:db/id :db.part/db :db.install/attribute (d/id-literal :test -9)}
+    :db/valueType   :db.type/ref
+    :db.install/_attribute :db.part/db}
    ])
 
 (deftest-async test-add-one
@@ -630,3 +629,31 @@
 
         (finally
           (<? (d/<close conn)))))))
+
+(deftest-async test-next-eid
+  (with-tempfile [t (tempfile)]
+    (let [conn      (<? (d/<connect t))
+          {tx0 :tx} (<? (d/<transact! conn test-schema))]
+      (testing "entids are increasing, tx ids are larger than user ids"
+        (let [r1 (<? (d/<transact! conn [{:db/id (d/id-literal :db.part/user -1) :name "Igor"}]))
+              r2 (<? (d/<transact! conn [{:db/id (d/id-literal :db.part/user -2) :name "Oleg"}]))
+              e1 (get (tempids r1) -1)
+              e2 (get (tempids r2) -2)]
+          (is (< e1 (:tx r1)))
+          (is (< e2 (:tx r2)))
+          (is (< e1 e2))
+          (is (< (:tx r1) (:tx r2)))
+
+          ;; Close and re-open same DB.
+          (<? (d/<close conn))
+          (let [conn (<? (d/<connect t))]
+            (try
+              (testing "entid counters are persisted across re-opens"
+                (let [r3 (<? (d/<transact! conn [{:db/id (d/id-literal :db.part/user -3) :name "Petr"}]))
+                      e3 (get (tempids r3) -3)]
+                  (is (< e3 (:tx r3)))
+                  (is (< e2 e3))
+                  (is (< (:tx r2) (:tx r3)))))
+
+              (finally
+                (<? (d/<close conn))))))))))
diff --git a/test/datomish/query_test.cljc b/test/datomish/query_test.cljc
index 0c6b3b17..33a8a259 100644
--- a/test/datomish/query_test.cljc
+++ b/test/datomish/query_test.cljc
@@ -29,7 +29,7 @@
    (def Throwable js/Error))
 
 (def test-schema
-  [{:db/id        (d/id-literal :test -1)
+  [{:db/id        (d/id-literal :db.part/user)
     :db/ident     :x
     :db/unique    :db.unique/identity
     :db/valueType :db.type/long
diff --git a/test/datomish/test.cljs b/test/datomish/test.cljs
index b7327d03..0800a06b 100644
--- a/test/datomish/test.cljs
+++ b/test/datomish/test.cljs
@@ -4,6 +4,7 @@
    [cljs.test :as t :refer-macros [is are deftest testing]]
    datomish.promise-sqlite-test
    datomish.db-test
+   datomish.query-test
    datomish.sqlite-user-version-test
    datomish.test.util
    datomish.test.transforms
@@ -13,6 +14,7 @@
 (doo-tests
   'datomish.promise-sqlite-test
   'datomish.db-test
+  'datomish.query-test
   'datomish.sqlite-user-version-test
   'datomish.test.util
   'datomish.test.transforms