[GitHub] [iotdb] haimeiguo commented on a change in pull request #2571: bug fix - fetch size calculation error for group by month

[GitBox <gi...@apache.org>]

haimeiguo commented on a change in pull request #2571:
URL: https://github.com/apache/iotdb/pull/2571#discussion_r565128057



##########
File path: server/src/main/java/org/apache/iotdb/db/service/TSServiceImpl.java
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@@ -668,6 +666,23 @@ private TSExecuteStatementResp internalExecuteQueryStatement(String statement, l
     }
   }
 
+  /*
+  calculate fetch size for group by time plan
+   */
+  private int getFetchSizeForGroupByTimePlan(GroupByTimePlan groupByTimePlan) {
+    int rows =  (int) ((groupByTimePlan.getEndTime() - groupByTimePlan.getStartTime()) / groupByTimePlan
+        .getInterval());
+    // edge case for group by months when starttime is in February
+    // ie. time range = [2020-02-02, 2020-03-02), interval = 1mo, rows will get 0
+    if (rows == 0 && groupByTimePlan.isIntervalByMonth()) {
+      Calendar calendar = Calendar.getInstance();
+      calendar.setTimeInMillis(groupByTimePlan.getStartTime());
+      calendar.add(Calendar.MONTH, (int) (groupByTimePlan.getInterval() / MS_TO_MONTH));
+      rows = calendar.getTimeInMillis() <= groupByTimePlan.getEndTime() ? 1 : 0;

Review comment:
       we add starttime by interval months to check if the group by interval is within starttime to endtime range which includes endtime itself. if we use < sign, the group by result is not correct for edge case 
   
   ie starttime = 2/1, endtime = 3/1 and interval = 1mo, we add 1 mo to 2/1, then calendar.getTimeInMillis() will be 3/1, which is equal to groupByTimePlan.getEndTime(), if use < sign, the result will not include 2/1 to 3/1 interval
   




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