fix NPE in search query when dimension contains null value (#3968)

* fix NPE when dimension contains null value in search query

* add ut

* search with not existed dimension should always return empty result

processing/src/main/java/io/druid/query/search/SearchQueryRunner.java

@@ -20,6 +20,7 @@
 package io.druid.query.search;
 
 import com.google.common.base.Function;
+import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
@@ -41,6 +42,7 @@ import io.druid.segment.ColumnValueSelector;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.FloatColumnSelector;
 import io.druid.segment.LongColumnSelector;
+import io.druid.segment.NullDimensionSelector;
 import io.druid.segment.Segment;
 import io.druid.segment.column.ColumnCapabilities;
 import io.druid.segment.column.ValueType;
@@ -126,12 +128,12 @@ public class SearchQueryRunner implements QueryRunner<Result<SearchResultValue>>
         final Object2IntRBTreeMap<SearchHit> set
     )
     {
-      if (selector != null) {
+      if (selector != null && !(selector instanceof NullDimensionSelector)) {
         final IndexedInts vals = selector.getRow();
         for (int i = 0; i < vals.size(); ++i) {
           final String dimVal = selector.lookupName(vals.get(i));
           if (searchQuerySpec.accept(dimVal)) {
-            set.addTo(new SearchHit(outputName, dimVal), 1);
+            set.addTo(new SearchHit(outputName, Strings.nullToEmpty(dimVal)), 1);
             if (set.size() >= limit) {
               return;
             }

processing/src/test/java/io/druid/query/search/SearchQueryRunnerTest.java

@@ -22,6 +22,8 @@ package io.druid.query.search;
 import com.google.common.base.Suppliers;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
+import io.druid.data.input.MapBasedInputRow;
+import io.druid.granularity.QueryGranularities;
 import io.druid.java.util.common.guava.Sequence;
 import io.druid.java.util.common.guava.Sequences;
 import io.druid.java.util.common.logger.Logger;
@@ -29,8 +31,10 @@ import io.druid.js.JavaScriptConfig;
 import io.druid.query.Druids;
 import io.druid.query.Query;
 import io.druid.query.QueryRunner;
+import io.druid.query.QueryRunnerFactory;
 import io.druid.query.QueryRunnerTestHelper;
 import io.druid.query.Result;
+import io.druid.query.aggregation.Aggregator;
 import io.druid.query.dimension.DefaultDimensionSpec;
 import io.druid.query.dimension.ExtractionDimensionSpec;
 import io.druid.query.extraction.ExtractionFn;
@@ -49,9 +53,14 @@ import io.druid.query.search.search.SearchQuery;
 import io.druid.query.search.search.SearchQueryConfig;
 import io.druid.query.search.search.SearchSortSpec;
 import io.druid.query.spec.MultipleIntervalSegmentSpec;
+import io.druid.segment.QueryableIndexSegment;
 import io.druid.segment.TestHelper;
+import io.druid.segment.TestIndex;
 import io.druid.segment.column.Column;
 import io.druid.segment.column.ValueType;
+import io.druid.segment.incremental.IncrementalIndex;
+import io.druid.segment.incremental.IncrementalIndexSchema;
+import io.druid.segment.incremental.OnheapIncrementalIndex;
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 import org.junit.Assert;
@@ -732,6 +741,70 @@ public class SearchQueryRunnerTest
     checkSearchQuery(searchQuery, expectedHits);
   }
 
+  @Test
+  public void testSearchWithNullValueInDimension() throws Exception
+  {
+    IncrementalIndex<Aggregator> index = new OnheapIncrementalIndex(
+        new IncrementalIndexSchema.Builder()
+            .withQueryGranularity(QueryGranularities.NONE)
+            .withMinTimestamp(new DateTime("2011-01-12T00:00:00.000Z").getMillis()).build(),
+        true,
+        10
+    );
+    index.add(
+        new MapBasedInputRow(
+            1481871600000L,
+            Arrays.asList("name", "host"),
+            ImmutableMap.<String, Object>of("name", "name1", "host", "host")
+        )
+    );
+    index.add(
+        new MapBasedInputRow(
+            1481871670000L,
+            Arrays.asList("name", "table"),
+            ImmutableMap.<String, Object>of("name", "name2", "table", "table")
+        )
+    );
+
+    SearchQuery searchQuery = Druids.newSearchQueryBuilder()
+                                    .dimensions(
+                                        new DefaultDimensionSpec("table", "table")
+                                    )
+                                    .dataSource(QueryRunnerTestHelper.dataSource)
+                                    .granularity(QueryRunnerTestHelper.allGran)
+                                    .intervals(QueryRunnerTestHelper.fullOnInterval)
+                                    // simulate when cardinality is big enough to fallback to cursorOnly strategy
+                                    .context(ImmutableMap.<String, Object>of("searchStrategy", "cursorOnly"))
+                                    .build();
+
+    QueryRunnerFactory factory = new SearchQueryRunnerFactory(
+        selector,
+        toolChest,
+        QueryRunnerTestHelper.NOOP_QUERYWATCHER
+    );
+    QueryRunner runner = factory.createRunner(new QueryableIndexSegment("asdf", TestIndex.persistRealtimeAndLoadMMapped(index)));
+    List<SearchHit> expectedHits = Lists.newLinkedList();
+    expectedHits.add(new SearchHit("table", "table", 1));
+    expectedHits.add(new SearchHit("table", "", 1));
+    checkSearchQuery(searchQuery, runner, expectedHits);
+  }
+
+  @Test
+  public void testSearchWithNotExistedDimension() throws Exception
+  {
+    SearchQuery searchQuery = Druids.newSearchQueryBuilder()
+                                    .dimensions(
+                                        new DefaultDimensionSpec("asdf", "asdf")
+                                    )
+                                    .dataSource(QueryRunnerTestHelper.dataSource)
+                                    .granularity(QueryRunnerTestHelper.allGran)
+                                    .intervals(QueryRunnerTestHelper.fullOnInterval)
+                                    .build();
+
+    List<SearchHit> noHit = Lists.newLinkedList();
+    checkSearchQuery(searchQuery, noHit);
+  }
+
   private void checkSearchQuery(Query searchQuery, List<SearchHit> expectedResults)
   {
     checkSearchQuery(searchQuery, runner, expectedResults);