From 9649525fe6bf686f57d24b3bc386675a100cea04 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Mon, 19 Oct 2020 02:53:47 -0500
Subject: [PATCH] Increase coverage and optimize history skip_initial_state
 (#42014)

Avoids a database query when all states have not
changed in the time window when skip_initial_state
is set.
---
 homeassistant/components/history/__init__.py | 25 +++++++++++--
 tests/components/history/test_init.py        | 38 ++++++++++++++++++++
 2 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/homeassistant/components/history/__init__.py b/homeassistant/components/history/__init__.py
index 79c60572ba5..a8ea18770d9 100644
--- a/homeassistant/components/history/__init__.py
+++ b/homeassistant/components/history/__init__.py
@@ -1,11 +1,11 @@
 """Provide pre-made queries on top of the recorder component."""
 from collections import defaultdict
-from datetime import timedelta
+from datetime import datetime as dt, timedelta
 from itertools import groupby
 import json
 import logging
 import time
-from typing import Optional, cast
+from typing import Iterable, Optional, cast
 
 from aiohttp import web
 from sqlalchemy import and_, bindparam, func, not_, or_
@@ -33,6 +33,7 @@ from homeassistant.helpers.entityfilter import (
     CONF_ENTITY_GLOBS,
     INCLUDE_EXCLUDE_BASE_FILTER_SCHEMA,
 )
+from homeassistant.helpers.typing import HomeAssistantType
 import homeassistant.util.dt as dt_util
 
 # mypy: allow-untyped-defs, no-check-untyped-defs
@@ -502,6 +503,13 @@ class HistoryPeriodView(HomeAssistantView):
 
         hass = request.app["hass"]
 
+        if (
+            not include_start_time_state
+            and entity_ids
+            and not _entities_may_have_state_changes_after(hass, entity_ids, start_time)
+        ):
+            return self.json([])
+
         return cast(
             web.Response,
             await hass.async_add_executor_job(
@@ -660,6 +668,19 @@ def _glob_to_like(glob_str):
     return States.entity_id.like(glob_str.translate(GLOB_TO_SQL_CHARS))
 
 
+def _entities_may_have_state_changes_after(
+    hass: HomeAssistantType, entity_ids: Iterable, start_time: dt
+) -> bool:
+    """Check the state machine to see if entities have changed since start time."""
+    for entity_id in entity_ids:
+        state = hass.states.get(entity_id)
+
+        if state is None or state.last_changed > start_time:
+            return True
+
+    return False
+
+
 class LazyState(State):
     """A lazy version of core State."""
 
diff --git a/tests/components/history/test_init.py b/tests/components/history/test_init.py
index d1ca3b50869..0b35d5194fb 100644
--- a/tests/components/history/test_init.py
+++ b/tests/components/history/test_init.py
@@ -970,3 +970,41 @@ async def test_entity_ids_limit_via_api(hass, hass_client):
     assert len(response_json) == 2
     assert response_json[0][0]["entity_id"] == "light.kitchen"
     assert response_json[1][0]["entity_id"] == "light.cow"
+
+
+async def test_entity_ids_limit_via_api_with_skip_initial_state(hass, hass_client):
+    """Test limiting history to entity_ids with skip_initial_state."""
+    await hass.async_add_executor_job(init_recorder_component, hass)
+    await async_setup_component(
+        hass,
+        "history",
+        {"history": {}},
+    )
+    await hass.async_add_executor_job(hass.data[recorder.DATA_INSTANCE].block_till_done)
+    hass.states.async_set("light.kitchen", "on")
+    hass.states.async_set("light.cow", "on")
+    hass.states.async_set("light.nomatch", "on")
+
+    await hass.async_block_till_done()
+
+    await hass.async_add_executor_job(trigger_db_commit, hass)
+    await hass.async_block_till_done()
+    await hass.async_add_executor_job(hass.data[recorder.DATA_INSTANCE].block_till_done)
+
+    client = await hass_client()
+    response = await client.get(
+        f"/api/history/period/{dt_util.utcnow().isoformat()}?filter_entity_id=light.kitchen,light.cow&skip_initial_state",
+    )
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json) == 0
+
+    when = dt_util.utcnow() - timedelta(minutes=1)
+    response = await client.get(
+        f"/api/history/period/{when.isoformat()}?filter_entity_id=light.kitchen,light.cow&skip_initial_state",
+    )
+    assert response.status == 200
+    response_json = await response.json()
+    assert len(response_json) == 2
+    assert response_json[0][0]["entity_id"] == "light.kitchen"
+    assert response_json[1][0]["entity_id"] == "light.cow"