Chart: Fix binary query, return first value (#2153)

server/lib/device/device.getDeviceFeaturesAggregates.js

@@ -24,53 +24,36 @@ const NON_BINARY_QUERY = `
 `;
 
 const BINARY_QUERY = `
-  WITH value_changes AS (
-      SELECT
-          created_at,
-          value,
-          LAG(value) OVER (ORDER BY created_at) AS prev_value
-      FROM
-          t_device_feature_state
-      WHERE
-          device_feature_id = ?
-          AND created_at > ?
-      ORDER BY
-          created_at DESC
-  ),
-  grouped_changes AS (
-      SELECT
-          created_at,
-          value,
-          CASE
-              WHEN value != LAG(value) OVER (ORDER BY created_at) THEN created_at
-              ELSE NULL
-          END AS change_marker
-      FROM
-          value_changes
-      ORDER BY
-          created_at DESC
-  ),
-  final_grouping AS (
-      SELECT
-          created_at AS start_time,
-          LEAD(created_at) OVER (ORDER BY created_at) AS end_time,
-          value
-      FROM
-          grouped_changes
-      WHERE
-          change_marker IS NOT NULL
-      ORDER BY
-          created_at DESC
-      LIMIT ?
-  )
-  SELECT
-      value,
-      start_time AS created_at,
-      end_time
-  FROM
-      final_grouping
-  ORDER BY
-      created_at ASC
+WITH value_changes AS (
+    SELECT
+        created_at,
+        value,
+        LAG(value) OVER (ORDER BY created_at) AS prev_value
+    FROM
+        t_device_feature_state
+    WHERE
+        device_feature_id = ?
+        AND created_at > ?
+),
+state_transitions AS (
+    SELECT
+        created_at,
+        value,
+        LEAD(created_at) OVER (ORDER BY created_at) AS end_time
+    FROM
+        value_changes
+    WHERE
+        prev_value IS NULL OR value != prev_value
+)
+SELECT
+    value,
+    created_at,
+    end_time
+FROM
+    state_transitions
+ORDER BY
+    created_at ASC
+LIMIT ?
 `;
 
 /**

server/test/lib/device/device.getDeviceFeaturesAggregates.test.js

@@ -244,6 +244,14 @@ describe('Device.getDeviceFeaturesAggregates binary feature', function Describe(
     expect(values).to.have.lengthOf(300);
     expect(device).to.have.property('name');
     expect(deviceFeature).to.have.property('name');
+
+    values.forEach((value) => {
+      expect(value).to.have.property('value');
+      // Check that both created_at and end_time are present
+      expect(value).to.have.property('created_at');
+      expect(value).to.have.property('end_time');
+    });
+
     // Check that the values are state changes
     for (let i = 1; i < values.length; i += 1) {
       expect(values[i].value).to.not.equal(values[i - 1].value);