fixing QPU db handling of history (#12)

entropylab_qpudb/_qpudatabase.py

@@ -130,7 +130,13 @@ def create_new_qpu_database(
     connection_hist = db_hist.open()
     root_hist = connection_hist.root()
     root_hist["entries"] = PersistentList(
-        [{"timestamp": datetime.utcnow(), "message": "initial commit"}]
+        [
+            {
+                "timestamp": datetime.utcnow(),
+                "connected_tx": None,
+                "message": "initial commit",
+            }
+        ]
     )
     transaction.commit()
     db_hist.close()
@@ -176,17 +182,15 @@ def __init__(self, dbname, history_index=None, path=None):
         self._db = None
         super().__init__()
         self._con_hist = self._open_hist_db()
-        self._readonly, self._con = self._open_data_db(history_index)
+        self._con = self._open_data_db(history_index)
 
     def _open_data_db(self, history_index):
         dbfilename = _db_file_from_path(self._path, self._dbname)
         hist_entries = self._con_hist.root()["entries"]
         if history_index is not None:
-            readonly = True
             message_index = history_index
-            at = self._con_hist.root()["entries"][history_index]["timestamp"]
+            at = self._con_hist.root()["entries"][history_index]["connected_tx"]
         else:
-            readonly = False
             message_index = len(hist_entries) - 1
             at = None
         try:
@@ -198,15 +202,12 @@ def _open_data_db(self, history_index):
             )
 
         con = self._db.open(transaction_manager=transaction.TransactionManager(), at=at)
-        assert (
-            con.isReadOnly() == readonly
-        ), "internal error: Inconsistent readonly state"
         con.transaction_manager.begin()
         print(
             f"opening qpu database {self._dbname} from "
             f"commit {self._str_hist_entry(hist_entries[message_index])} at index {message_index}"
         )
-        return readonly, con
+        return con
 
     def _open_hist_db(self):
         histfilename = _hist_file_from_path(self._path, self._dbname)
@@ -226,7 +227,7 @@ def __enter__(self):
 
     @property
     def readonly(self):
-        return self._readonly
+        return self._con.isReadOnly()
 
     def close(self) -> None:
         """
@@ -331,7 +332,7 @@ def commit(self, message: Optional[str] = None) -> None:
         Permanently store the existing state to the DB and add a new commit to the history list
         :param message: an optional message for the commit
         """
-        if self._readonly:
+        if self.readonly:
             raise ReadOnlyError("Attempting to commit to a DB in a readonly state")
         lt_before = self._con._db.lastTransaction()
         self._con.transaction_manager.commit()
@@ -340,7 +341,9 @@ def commit(self, message: Optional[str] = None) -> None:
             hist_root = self._con_hist.root()
             hist_entries = hist_root["entries"]
             now = datetime.utcnow()
-            hist_entries.append({"timestamp": now, "message": message})
+            hist_entries.append(
+                {"timestamp": now, "connected_tx": lt_after, "message": message}
+            )
             self._con_hist.transaction_manager.commit()
             print(
                 f"commiting qpu database {self._dbname} "
@@ -384,7 +387,7 @@ def restore_from_history(self, history_index: int) -> None:
 
         :param history_index: History index from which to restore
         """
-        readonly, con = self._open_data_db(history_index)
+        con = self._open_data_db(history_index)
         self._con.root()["elements"] = deepcopy(con.root()["elements"])
         con.close()
 

entropylab_qpudb/tests/test_qpudatabase.py

@@ -239,13 +239,13 @@ def test_fail_on_commit_to_readonly(testdb):
     # open historical connection
 
     # should fail when DB is modified
-    with QpuDatabaseConnection(testdb, simp_resolver, history_index=0) as db:
+    with QpuDatabaseConnection(testdb, simp_resolver, history_index=1) as db:
         db.set("q1", "p1", 444)
         with pytest.raises(ReadOnlyError):
             db.commit("trying")
 
     # should fail when DB is not modified
-    with QpuDatabaseConnection(testdb, simp_resolver, history_index=0) as db:
+    with QpuDatabaseConnection(testdb, simp_resolver, history_index=1) as db:
         with pytest.raises(ReadOnlyError):
             db.commit("trying")
 
@@ -262,15 +262,17 @@ def test_commit_unmodified(testdb):
 
 def test_restore_from_history(testdb):
     with QpuDatabaseConnection(testdb, simp_resolver) as db:
+        db.set("q2", "p1", 3.4)
+        db.commit("my first commit")
         print()
         db.set("q2", "p1", 11.0)
         print(db.get("q2", "p1"))
-        db.commit("my first commit")
+        db.commit("my second commit")
 
     with QpuDatabaseConnection(testdb, simp_resolver) as db:
         print()
         assert db.get("q2", "p1").value == 11.0
-        db.restore_from_history(0)
+        db.restore_from_history(1)
         print(db.get("q2", "p1"))
         assert db.get("q2", "p1").value == 3.4
 
@@ -381,3 +383,46 @@ def test_use_in_entropy(testdb, simp_resolver):
         experiment_resources.get_resource(testdb).close()
     finally:
         os.remove("entropy.db")
+
+
+def test_we_can_open_all_history_items(testdb):
+    indices = []
+    expected_values = []
+    actual_values = []
+
+    # prepare the database with items in the history
+    with QpuDatabaseConnection(testdb) as db:
+        for v_bias in range(6):
+            db.set("q1", "p1", v_bias)
+            db.commit()
+            indices.append(len(db._con_hist.root()["entries"]) - 1)
+            expected_values.append(db.q(1).p1.value)
+
+    # try to pull an item from all history entries
+    with QpuDatabaseConnection(testdb) as db:
+        for i in indices:
+            db.restore_from_history(i)
+            actual_values.append(db.q(1).p1.value)
+
+    assert expected_values == actual_values
+
+
+def test_we_can_open_all_history_items_in_same_connection(testdb):
+    indices = []
+    expected_values = []
+    actual_values = []
+
+    # prepare the database with items in the history
+    with QpuDatabaseConnection(testdb) as db:
+        for v_bias in range(6):
+            db.set("q1", "p1", v_bias)
+            db.commit()
+            indices.append(len(db._con_hist.root()["entries"]) - 1)
+            expected_values.append(db.q(1).p1.value)
+
+        # try to pull an item from all history entries
+        for i in indices:
+            db.restore_from_history(i)
+            actual_values.append(db.q(1).p1.value)
+
+    assert expected_values == actual_values