Improve performance of Score computation

app/src/main/java/org/isoron/uhabits/models/ScoreList.java

@@ -31,6 +31,7 @@ import com.activeandroid.query.From;
 import com.activeandroid.query.Select;
 import com.activeandroid.util.SQLiteUtils;
 
+import org.isoron.uhabits.helpers.DatabaseHelper;
 import org.isoron.uhabits.helpers.DateHelper;
 
 import java.io.IOException;
@@ -61,31 +62,6 @@ public class ScoreList
                 .orderBy("timestamp desc");
     }
 
-    /**
-     * Returns the most recent score already computed. If no score has been computed yet, returns
-     * null.
-     *
-     * @return newest score, or null if none exist
-     */
-    @Nullable
-    protected Score findNewest()
-    {
-        return select().limit(1).executeSingle();
-    }
-
-    /**
-     * Returns the value of the most recent score that was already computed. If no score has been
-     * computed yet, returns zero.
-     *
-     * @return value of newest score, or zero if none exist
-     */
-    protected int findNewestValue()
-    {
-        Score newest = findNewest();
-        if(newest == null) return 0;
-        else return newest.score;
-    }
-
     /**
      * Marks all scores that have timestamp equal to or newer than the given timestamp as invalid.
      * Any following getValue calls will trigger the scores to be recomputed.
@@ -130,15 +106,14 @@ public class ScoreList
         final double freq = ((double) habit.freqNum) / habit.freqDen;
 
         int newestScoreValue = findNewestValue();
-        Score newestScore = findNewest();
+        long newestTimestamp = findNewestTimestamp();
 
-        if(newestScore != null)
-            from = newestScore.timestamp + day;
+        if(newestTimestamp > 0)
+            from = newestTimestamp + day;
 
         final int checkmarkValues[] = habit.checkmarks.getValues(from, to);
         final long beginning = from;
 
-
         int lastScore = newestScoreValue;
         int size = checkmarkValues.length;
 
@@ -156,6 +131,26 @@ public class ScoreList
         insert(timestamps, values);
     }
 
+    /**
+     * Returns the value of the most recent score that was already computed. If no score has been
+     * computed yet, returns zero.
+     *
+     * @return value of newest score, or zero if none exist
+     */
+    protected int findNewestValue()
+    {
+        String args[] = { habit.getId().toString() };
+        String query = "select score from Score where habit = ? order by timestamp desc limit 1";
+        return SQLiteUtils.intQuery(query, args);
+    }
+
+    private long findNewestTimestamp()
+    {
+        String args[] = { habit.getId().toString() };
+        String query = "select timestamp from Score where habit = ? order by timestamp desc limit 1";
+        return DatabaseHelper.longQuery(query, args);
+    }
+
     private void insert(long timestamps[], long values[])
     {
         String query = "insert into Score(habit, timestamp, score) values (?,?,?)";