BufferArrayGrouper: Fix potential overflow in requiredBufferCapacity. (#9435)

* BufferArrayGrouper: Fix potential overflow in requiredBufferCapacity.

If cardinality was high, the computation could overflow an int. There
were tests for this, but the tests were wrong.

* Nicer.

processing/src/main/java/org/apache/druid/query/groupby/epinephelinae/BufferArrayGrouper.java

@@ -21,6 +21,7 @@ package org.apache.druid.query.groupby.epinephelinae;
 
 import com.google.common.base.Preconditions;
 import com.google.common.base.Supplier;
+import com.google.common.primitives.Ints;
 import org.apache.datasketches.memory.Memory;
 import org.apache.datasketches.memory.WritableMemory;
 import org.apache.druid.java.util.common.IAE;
@@ -73,19 +74,24 @@ public class BufferArrayGrouper implements VectorGrouper, IntGrouper
       AggregatorFactory[] aggregatorFactories
   )
   {
-    final int cardinalityWithMissingValue = cardinality + 1;
-    final int recordSize = Arrays.stream(aggregatorFactories)
-                                 .mapToInt(AggregatorFactory::getMaxIntermediateSizeWithNulls)
+    final long cardinalityWithMissingValue = computeCardinalityWithMissingValue(cardinality);
+    final long recordSize = Arrays.stream(aggregatorFactories)
+                                  .mapToLong(AggregatorFactory::getMaxIntermediateSizeWithNulls)
                                   .sum();
 
     return getUsedFlagBufferCapacity(cardinalityWithMissingValue) +  // total used flags size
-           (long) cardinalityWithMissingValue * recordSize;                 // total values size
+           cardinalityWithMissingValue * recordSize;                 // total values size
+  }
+
+  private static long computeCardinalityWithMissingValue(int cardinality)
+  {
+    return (long) cardinality + 1;
   }
 
   /**
    * Compute the number of bytes to store all used flag bits.
    */
-  private static int getUsedFlagBufferCapacity(int cardinalityWithMissingValue)
+  private static long getUsedFlagBufferCapacity(long cardinalityWithMissingValue)
   {
     return (cardinalityWithMissingValue + Byte.SIZE - 1) / Byte.SIZE;
   }
@@ -102,7 +108,7 @@ public class BufferArrayGrouper implements VectorGrouper, IntGrouper
 
     this.bufferSupplier = Preconditions.checkNotNull(bufferSupplier, "bufferSupplier");
     this.aggregators = aggregators;
-    this.cardinalityWithMissingValue = cardinality + 1;
+    this.cardinalityWithMissingValue = Ints.checkedCast(computeCardinalityWithMissingValue(cardinality));
     this.recordSize = aggregators.spaceNeeded();
   }
 
@@ -112,7 +118,7 @@ public class BufferArrayGrouper implements VectorGrouper, IntGrouper
     if (!initialized) {
       final ByteBuffer buffer = bufferSupplier.get();
 
-      final int usedFlagBufferEnd = getUsedFlagBufferCapacity(cardinalityWithMissingValue);
+      final int usedFlagBufferEnd = Ints.checkedCast(getUsedFlagBufferCapacity(cardinalityWithMissingValue));
 
       // Sanity check on buffer capacity.
       if (usedFlagBufferEnd + (long) cardinalityWithMissingValue * recordSize > buffer.capacity()) {

processing/src/test/java/org/apache/druid/query/groupby/epinephelinae/BufferArrayGrouperTest.java

@@ -27,12 +27,14 @@ import com.google.common.collect.Ordering;
 import com.google.common.primitives.Ints;
 import org.apache.druid.common.config.NullHandling;
 import org.apache.druid.data.input.MapBasedRow;
+import org.apache.druid.java.util.common.StringUtils;
 import org.apache.druid.query.aggregation.AggregatorAdapters;
 import org.apache.druid.query.aggregation.AggregatorFactory;
 import org.apache.druid.query.aggregation.CountAggregatorFactory;
 import org.apache.druid.query.aggregation.LongSumAggregatorFactory;
 import org.apache.druid.query.groupby.epinephelinae.Grouper.Entry;
 import org.junit.Assert;
+import org.junit.BeforeClass;
 import org.junit.Test;
 
 import java.nio.ByteBuffer;
@@ -41,6 +43,12 @@ import java.util.List;
 
 public class BufferArrayGrouperTest
 {
+  @BeforeClass
+  public static void setUpStatic()
+  {
+    NullHandling.initializeForTests();
+  }
+
   @Test
   public void testAggregate()
   {
@@ -94,23 +102,29 @@ public class BufferArrayGrouperTest
   @Test
   public void testRequiredBufferCapacity()
   {
-    int[] cardinalityArray = new int[]{1, 10, Integer.MAX_VALUE - 1};
-    AggregatorFactory[] aggregatorFactories = new AggregatorFactory[]{
+    final int[] cardinalityArray = new int[]{1, 10, Integer.MAX_VALUE - 1, Integer.MAX_VALUE};
+    final AggregatorFactory[] aggregatorFactories = new AggregatorFactory[]{
         new LongSumAggregatorFactory("sum", "sum")
     };
-    long[] requiredSizes;
+
+    final long[] requiredSizes;
+
     if (NullHandling.sqlCompatible()) {
       // We need additional size to store nullability information.
-      requiredSizes = new long[]{19, 101, 19058917368L};
+      requiredSizes = new long[]{19, 101, 19595788279L, 19595788288L};
     } else {
-      requiredSizes = new long[]{17, 90, 16911433721L};
+      requiredSizes = new long[]{17, 90, 17448304632L, 17448304640L};
     }
 
     for (int i = 0; i < cardinalityArray.length; i++) {
-      Assert.assertEquals(requiredSizes[i], BufferArrayGrouper.requiredBufferCapacity(
+      Assert.assertEquals(
+          StringUtils.format("cardinality[%d]", cardinalityArray[i]),
+          requiredSizes[i],
+          BufferArrayGrouper.requiredBufferCapacity(
               cardinalityArray[i],
               aggregatorFactories
-      ));
+          )
+      );
     }
   }
 }