Avoid additional timestamp conversion to set state (#118885)

Avoid addtional timestamp conversion to set state

Since we already have the timestamp, we can pass it on to the State
object and avoid the additional timestamp conversion which can be as
much as 30% of the state write runtime.

Since datetime objects are limited to microsecond precision, we need
to adjust some tests to account for the additional precision that we
will now be able to get in the database

tests/test_core.py

@@ -2834,8 +2834,32 @@ async def test_state_change_events_context_id_match_state_time(
     assert state.last_updated == events[0].time_fired
     assert len(state.context.id) == 26
     # ULIDs store time to 3 decimal places compared to python timestamps
-    assert _ulid_timestamp(state.context.id) == int(
-        state.last_updated.timestamp() * 1000
+    assert _ulid_timestamp(state.context.id) == int(state.last_updated_timestamp * 1000)
+
+
+async def test_state_change_events_match_time_with_limits_of_precision(
+    hass: HomeAssistant,
+) -> None:
+    """Ensure last_updated matches last_updated_timestamp within limits of precision.
+
+    The last_updated_timestamp uses the same precision as time.time() which is
+    a bit better than the precision of datetime.now() which is used for last_updated
+    on some platforms.
+    """
+    events = async_capture_events(hass, ha.EVENT_STATE_CHANGED)
+    hass.states.async_set("light.bedroom", "on")
+    await hass.async_block_till_done()
+    state: State = hass.states.get("light.bedroom")
+    assert state.last_updated == events[0].time_fired
+    assert state.last_updated_timestamp == pytest.approx(
+        events[0].time_fired.timestamp()
+    )
+    assert state.last_updated_timestamp == pytest.approx(state.last_updated.timestamp())
+    assert state.last_updated_timestamp == state.last_changed_timestamp
+    assert state.last_updated_timestamp == pytest.approx(state.last_changed.timestamp())
+    assert state.last_updated_timestamp == state.last_reported_timestamp
+    assert state.last_updated_timestamp == pytest.approx(
+        state.last_reported.timestamp()
     )