fix(grafana): harden latest-reading queries

Author: Magrathean UK

grafana/dashboards/battery-health.json

@@ -1089,7 +1089,7 @@
           "editorMode": "code",
           "format": "table",
           "rawQuery": true,
-          "rawSql": "SELECT * FROM ((SELECT usable_battery_level, date\r\nFROM positions\r\nWHERE car_id = $car_id AND ideal_battery_range_km IS NOT NULL AND usable_battery_level IS NOT NULL\r\nORDER BY date DESC\r\nLIMIT 1)\r\nUNION\r\n(SELECT usable_battery_level, date\r\nFROM charges c\r\nJOIN charging_processes p ON p.id = c.charging_process_id\r\nWHERE p.car_id = $car_id AND usable_battery_level IS NOT NULL\r\nORDER BY date DESC\r\nLIMIT 1)) AS last_usable_battery_level LIMIT 1",
+          "rawSql": "SELECT * FROM ((SELECT usable_battery_level, date\r\nFROM positions\r\nWHERE car_id = $car_id AND ideal_battery_range_km IS NOT NULL AND usable_battery_level IS NOT NULL\r\nORDER BY date DESC\r\nLIMIT 1)\r\nUNION ALL\r\n(SELECT c.usable_battery_level, date\r\nFROM charges c\r\nJOIN charging_processes p ON p.id = c.charging_process_id\r\nWHERE p.car_id = $car_id AND c.usable_battery_level IS NOT NULL\r\nORDER BY date DESC\r\nLIMIT 1)) AS last_usable_battery_level ORDER BY date DESC LIMIT 1",
           "refId": "SOC",
           "sql": {
             "columns": [
@@ -1365,7 +1365,7 @@
           "editorMode": "code",
           "format": "table",
           "rawQuery": true,
-          "rawSql": "SELECT * FROM ((SELECT usable_battery_level * ('$aux'::json ->> 'CurrentCapacity')::float / 100 as kWh, date, ('$aux'::json ->> 'CurrentCapacity')::float as Total\nFROM positions\nWHERE car_id = $car_id AND ideal_battery_range_km IS NOT NULL AND usable_battery_level IS NOT NULL\nORDER BY date DESC\nLIMIT 1)\nUNION\n(SELECT c.usable_battery_level * ('$aux'::json ->> 'CurrentCapacity')::float / 100 as kWh, date, ('$aux'::json ->> 'CurrentCapacity')::float as Total\nFROM charges c\nJOIN charging_processes p ON p.id = c.charging_process_id\nWHERE p.car_id = $car_id  AND c.usable_battery_level IS NOT NULL\nORDER BY date DESC\nLIMIT 1)) AS last_usable_battery_level LIMIT 1",
+          "rawSql": "SELECT * FROM ((SELECT usable_battery_level * ('$aux'::json ->> 'CurrentCapacity')::float / 100 as kWh, date, ('$aux'::json ->> 'CurrentCapacity')::float as Total\nFROM positions\nWHERE car_id = $car_id AND ideal_battery_range_km IS NOT NULL AND usable_battery_level IS NOT NULL\nORDER BY date DESC\nLIMIT 1)\nUNION ALL\n(SELECT c.usable_battery_level * ('$aux'::json ->> 'CurrentCapacity')::float / 100 as kWh, date, ('$aux'::json ->> 'CurrentCapacity')::float as Total\nFROM charges c\nJOIN charging_processes p ON p.id = c.charging_process_id\nWHERE p.car_id = $car_id  AND c.usable_battery_level IS NOT NULL\nORDER BY date DESC\nLIMIT 1)) AS last_usable_battery_level ORDER BY date DESC LIMIT 1",
           "refId": "A",
           "sql": {
             "columns": [

test/teslamate/grafana/dashboard_queries_test.exs

@@ -13,7 +13,7 @@ defmodule TeslaMate.Grafana.DashboardQueriesTest do
   #
   # `(?:(?!\bfrom\b).)*?` keeps a match from spilling across into a following
   # `FROM charges`/CTE, so the filter must appear inside the *same* positions block.
-  @latest_position_block ~r/from positions\b(?:(?!\bfrom\b).)*?order by date desc(?:(?!\bfrom\b).)*?limit 1/
+  @latest_position_block ~r/from positions\b(?:(?!\bfrom\b).)*?order by date desc(?:(?!\bfrom\b).)*?limit 1\b/
 
   test "latest position queries use complete position rows" do
     offenders =
@@ -48,6 +48,35 @@ defmodule TeslaMate.Grafana.DashboardQueriesTest do
     assert unfiltered_latest_position_blocks(query) == []
   end
 
+  test "detector ignores queries with a larger limit" do
+    query = "SELECT date FROM positions WHERE car_id = 1 ORDER BY date DESC LIMIT 10"
+
+    assert unfiltered_latest_position_blocks(query) == []
+  end
+
+  test "latest usable battery unions select the newest source row" do
+    queries =
+      "grafana/dashboards/battery-health.json"
+      |> dashboard_queries()
+      |> Enum.map(fn {_path, query} ->
+        query
+        |> String.downcase()
+        |> String.replace(~r/\s+/, " ")
+      end)
+      |> Enum.filter(&String.contains?(&1, "last_usable_battery_level"))
+
+    assert length(queries) == 2
+
+    for query <- queries do
+      assert String.contains?(query, "union all")
+
+      assert String.contains?(
+               query,
+               "as last_usable_battery_level order by date desc limit 1"
+             )
+    end
+  end
+
   defp dashboard_queries(path) do
     path
     |> File.read!()