[GitHub] [druid] suneet-s commented on a change in pull request #10742: Granularity interval materialization

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suneet-s commented on a change in pull request #10742:
URL: https://github.com/apache/druid/pull/10742#discussion_r562319912



##########
File path: core/src/main/java/org/apache/druid/java/util/common/granularity/IntervalsByGranularity.java
##########
@@ -0,0 +1,144 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.java.util.common.granularity;
+
+import com.google.common.collect.Iterators;
+import com.google.common.collect.PeekingIterator;
+import com.google.common.collect.Sets;
+import org.apache.druid.java.util.common.guava.Comparators;
+import org.joda.time.Interval;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+/**
+ * Produce a stream of intervals generated by a given set of intervals as input and a given
+ * granularity. This class avoids materializing the granularity intervals whenever possible.
+ */
+public class IntervalsByGranularity
+{
+  private final List<Interval> sortedIntervals;
+  private final Granularity granularity;
+
+  public IntervalsByGranularity(Collection<Interval> intervals, Granularity granularity)
+  {
+    // eliminate dups & sort intervals:
+    HashSet<Interval> intervalSet = Sets.newHashSetWithExpectedSize(intervals.size());
+    intervalSet.addAll(intervals);
+    this.sortedIntervals = new ArrayList<>(intervals.size());
+    this.sortedIntervals.addAll(intervalSet);
+    this.sortedIntervals.sort(Comparators.intervalsByStartThenEnd());
+
+    this.granularity = granularity;
+  }
+
+  public Iterator<Interval> granularityIntervalsIterator()
+  {
+    Iterator<Interval> ite;
+    if (sortedIntervals.isEmpty()) {
+      ite = Collections.emptyIterator();
+    } else {
+      ite = new IntervalIterator(sortedIntervals);
+    }
+    return ite;
+  }
+
+  private class IntervalIterator implements Iterator<Interval>
+  {
+    private final List<Interval> sortedIntervals;
+    private int currentInterval;
+    private volatile PeekingIterator<Interval> currentIterator;
+    private Interval previous;
+
+    public IntervalIterator(List<Interval> sortedIntervals)
+    {
+      this.sortedIntervals = sortedIntervals;
+      this.currentInterval = 0;
+      currentIterator =
+          Iterators.peekingIterator(granularity.getIterable(sortedIntervals.get(currentInterval)).iterator());
+    }
+
+    @Override
+    public boolean hasNext()
+    {
+      if (currentIterator != null) {
+        boolean advance = false;
+        while (true) {
+
+          // is it time to move to the next iterator?
+          if (advance) {
+            if (currentInterval < sortedIntervals.size() - 1) {
+              currentIterator =
+                  Iterators.peekingIterator(granularity.getIterable(sortedIntervals.get(++currentInterval)).iterator());
+              advance = false;
+            } else {
+              break;
+            }
+          }
+
+          // check if this iterator has more elements:
+          if (currentIterator.hasNext()) {
+
+            // drop all subsequent intervals that are the same as the previous...
+            while (previous != null && previous.equals(currentIterator.peek())) {
+              currentIterator.next(); // drop it like it's hot
+              if (!currentIterator.hasNext()) {
+                advance = true;
+                break;
+              }
+            }
+            if (advance) {
+              continue; // no more here, get to the next iterator...
+            }
+
+            return true; // there are more
+
+          } else {
+            advance = true; // no more
+          }
+
+        } // while true
+      }
+      return false;
+    }

Review comment:
       Looks like CI is complaining about a lack of test coverage for this class - how is this being tested?




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