improve StatFilter

src/main/java/com/alibaba/druid/stat/JdbcSqlStat.java

@@ -335,10 +335,11 @@ public final class JdbcSqlStat implements JdbcSqlStatMBean {
     }
 
     public void addExecuteTime(StatementExecuteType executeType, boolean firstResultSet, long nanoSpan) {
+        addExecuteTime(nanoSpan);
+        
         if (StatementExecuteType.ExecuteQuery != executeType && !firstResultSet) {
             executeAndResultHoldTimeHistogram.record((nanoSpan) / 1000 / 1000);
         }
-        addExecuteTime(nanoSpan);
     }
 
     public void addExecuteTime(long nanoSpan) {

src/main/java/com/alibaba/druid/util/Histogram.java

@@ -81,6 +81,14 @@ public class Histogram {
         return rangeCounters[index].get();
     }
     
+    public long getSum() {
+        long sum = 0;
+        for (int i = 0; i < rangeCounters.length; ++i) {
+            sum += rangeCounters[i].get();
+        }
+        return sum;
+    }
+    
     public String toString() {
     	StringBuilder buf = new StringBuilder();
     	buf.append('[');