[GitHub] [druid] gianm commented on a change in pull request #10968: fix SQL issue for group by queries with time filter that gets optimized to false

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

gianm commented on a change in pull request #10968:
URL: https://github.com/apache/druid/pull/10968#discussion_r590591364



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File path: sql/src/main/java/org/apache/druid/sql/calcite/filtration/CombineAndSimplifyBounds.java
##########
@@ -130,15 +134,24 @@ private static DimFilter doSimplify(final List<DimFilter> children, boolean disj
     // Group Bound filters by dimension, extractionFn, and comparator and compute a RangeSet for each one.
     final Map<BoundRefKey, List<BoundDimFilter>> bounds = new HashMap<>();
 
+    boolean allFalse = true;

Review comment:
       Will `children` ever be empty? If not, consider including a precondition check. If it could be empty: then, if it is empty, this will return a `Filtration.matchNothing()`. Is that OK?

##########
File path: processing/src/main/java/org/apache/druid/query/groupby/GroupByQuery.java
##########
@@ -715,7 +716,11 @@ private DateTime computeUniversalTimestamp()
     if (!timestampStringFromContext.isEmpty()) {
       return DateTimes.utc(Long.parseLong(timestampStringFromContext));
     } else if (Granularities.ALL.equals(granularity)) {
-      final DateTime timeStart = getIntervals().get(0).getStart();
+      final List<Interval> intervals = getIntervals();
+      if (CollectionUtils.isNullOrEmpty(intervals)) {
+        return null;

Review comment:
       Why is `null` correct instead of some specific timestamp? (Whatever the answer is, IMO it'd be good as a comment.)




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