Support descending range iteration in MapIndexStore

geode-core/src/integrationTest/java/org/apache/geode/cache/query/internal/index/CompactRangeIndexIndexMapJUnitTest.java

@@ -20,6 +20,7 @@
 
 import java.text.ParseException;
 import java.util.HashMap;
+import java.util.Iterator;
 
 import org.junit.After;
 import org.junit.Before;
@@ -115,6 +116,45 @@ public void testMultipleSecondLevelMatches() throws Exception {
     IndexManager.IS_TEST_EXPANSION = oldTestExpansionValue;
   }
 
+  @Test
+  public void testDescendingRangeQueryWithLimitReturnsSameOrderForMapIndexStore() throws Exception {
+    String queryString = "Select * from " + SEPARATOR
+        + "portfolios p where p.ID >= 2 and p.ID <= 7 order by p.ID desc limit 3";
+
+    Cache cache = CacheUtils.getCache();
+    QueryService queryService = cache.getQueryService();
+    int numEntries = 20;
+    boolean oldTestLDMValue = IndexManager.IS_TEST_LDM;
+    boolean oldTestExpansionValue = IndexManager.IS_TEST_EXPANSION;
+
+    try {
+      IndexManager.IS_TEST_LDM = false;
+      IndexManager.IS_TEST_EXPANSION = false;
+      Region region = createReplicatedRegion("portfolios");
+      createPortfolios(region, numEntries);
+
+      queryService.createIndex("IDIndex", "p.ID", SEPARATOR + "portfolios p");
+      SelectResults memResults = (SelectResults) queryService.newQuery(queryString).execute();
+      validatePortfolioOrder(memResults, 7, 6, 5);
+      queryService.removeIndexes();
+      region.destroyRegion();
+
+      IndexManager.IS_TEST_LDM = true;
+      IndexManager.IS_TEST_EXPANSION = true;
+      region = createLDMRegion("portfolios");
+      createPortfolios(region, numEntries);
+
+      queryService.createIndex("IDIndex", "p.ID", SEPARATOR + "portfolios p");
+      SelectResults ldmResults = (SelectResults) queryService.newQuery(queryString).execute();
+      validatePortfolioOrder(ldmResults, 7, 6, 5);
+      queryService.removeIndexes();
+      region.destroyRegion();
+    } finally {
+      IndexManager.IS_TEST_LDM = oldTestLDMValue;
+      IndexManager.IS_TEST_EXPANSION = oldTestExpansionValue;
+    }
+  }
+
   // executes queries against both no index and ldm index
   // compares size counts of both and compares results
   private void testIndexAndQuery(String indexExpression, String regionPath, String queryString)
@@ -187,6 +227,16 @@ private Region createReplicatedRegion(String regionName) throws ParseException {
     return cache.createRegion(regionName, regionAttributes);
   }
 
+  private void validatePortfolioOrder(SelectResults results, int... expectedIds) {
+    assertEquals("Unexpected result size", expectedIds.length, results.size());
+    Iterator iterator = results.iterator();
+    for (int expectedId : expectedIds) {
+      Portfolio portfolio = (Portfolio) iterator.next();
+      assertEquals("Unexpected portfolio order", expectedId, portfolio.getID());
+    }
+    assertEquals("Returned more results than expected", false, iterator.hasNext());
+  }
+
   private void createPortfolios(Region region, int num) {
     for (int i = 0; i < num; i++) {
       Portfolio p = new Portfolio(i);

geode-core/src/integrationTest/java/org/apache/geode/cache/query/internal/index/MapIndexStoreJUnitTest.java

@@ -163,6 +163,23 @@ private void validateDescendingIterator(CloseableIterator iterator, int reverseS
     }
   }
 
+  private void validateDescendingRangeIterator(CloseableIterator<IndexStoreEntry> iterator,
+      int reverseStart, int reverseEndInclusive) {
+    try {
+      for (int i = reverseStart; i >= reverseEndInclusive; i--) {
+        IndexStoreEntry ise = iterator.next();
+        if (Integer.parseInt((String) ise.getDeserializedKey()) != i) {
+          fail("descending range iterator did not return the expected reverse order");
+        }
+      }
+      assertEquals("descending range iterator returned extra values", false, iterator.hasNext());
+    } finally {
+      if (iterator != null) {
+        iterator.close();
+      }
+    }
+  }
+
   /**
    * Helper method to test index storage iterators
    */
@@ -283,6 +300,26 @@ public void testStartExclusiveEndInclusive() throws IMQException {
     helpTestStartAndEndIterator(region, startValue, true, endValue, false, numValues - 1);
   }
 
+  @Test
+  public void testDescendingRangeIteratorReturnsReverseOrder() throws IMQException {
+    addValues(region, numValues);
+
+    CloseableIterator<IndexStoreEntry> iterator =
+        indexDataStructure.descendingIterator("2", true, "7", true, null);
+
+    validateDescendingRangeIterator(iterator, 7, 2);
+  }
+
+  @Test
+  public void testDescendingRangeIteratorHonorsExclusiveBounds() throws IMQException {
+    addValues(region, numValues);
+
+    CloseableIterator<IndexStoreEntry> iterator =
+        indexDataStructure.descendingIterator("2", false, "7", false, null);
+
+    validateDescendingRangeIterator(iterator, 6, 3);
+  }
+
 
 
   private class IndexRegionTestEntry implements IndexStoreEntry {

geode-core/src/main/java/org/apache/geode/cache/query/internal/index/MapIndexStore.java

@@ -145,9 +145,12 @@ public CloseableIterator<IndexStoreEntry> descendingIterator(Collection keysToRe
   @Override
   public CloseableIterator<IndexStoreEntry> descendingIterator(Object start, boolean startInclusive,
       Object end, boolean endInclusive, Collection keysToRemove) {
-    // @todo change to descending once it is supported
-    return new MapIndexStoreIterator(indexMap.iterator(start, startInclusive, end, endInclusive),
-        keysToRemove, indexOnValues, indexOnRegionKeys);
+    if (start == null) {
+      return descendingIterator(end, endInclusive, keysToRemove);
+    }
+    return new MapIndexStoreIterator(
+        indexMap.descendingIterator(start, startInclusive, end, endInclusive), keysToRemove,
+        indexOnValues, indexOnRegionKeys);
   }
 
   @Override

geode-core/src/main/java/org/apache/geode/internal/cache/persistence/query/IndexMap.java

@@ -95,6 +95,12 @@ CloseableIterator<IndexEntry> iterator(Object start, boolean startInclusive, Obj
    */
   CloseableIterator<IndexEntry> descendingIterator();
 
+  /**
+   * Return all of the IndexEntries in the range between start and end, in descending order.
+   */
+  CloseableIterator<IndexEntry> descendingIterator(Object start, boolean startInclusive,
+      Object end, boolean endInclusive);
+
   /**
    * Return all of the region keys from start to end.
    */

geode-core/src/main/java/org/apache/geode/internal/cache/persistence/query/mock/IndexMapImpl.java

@@ -106,6 +106,16 @@ public CloseableIterator<IndexEntry> descendingIterator() {
     return new Itr(map.descendingMap().entrySet().iterator());
   }
 
+  @Override
+  public CloseableIterator<IndexEntry> descendingIterator(Object start, boolean startInclusive,
+      Object end, boolean endInclusive) {
+    byte[] startBytes = startInclusive ? ByteComparator.MIN_BYTES : ByteComparator.MAX_BYTES;
+    byte[] endBytes = endInclusive ? ByteComparator.MAX_BYTES : ByteComparator.MIN_BYTES;
+    return new Itr(map
+        .subMap(new Pair(start, startBytes), startInclusive, new Pair(end, endBytes), endInclusive)
+        .descendingMap().entrySet().iterator());
+  }
+
   @Override
   public CloseableIterator<CachedDeserializable> keyIterator(Object start, boolean startInclusive,
       Object end, boolean endInclusive) {