fix count return null (apache#6118)

* fix count return null * fix checkstyle * fix unit test * polish checkstyle * polish code style * fix in getMemoryResultSetRows * fix code style * extract method * fix codestyle
sandynz · Jun 19, 2020 · f9d0903 · f9d0903
1 parent cd9a11b
commit f9d0903
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Showing 3 changed files with 23 additions and 2 deletions.
diff --git a/.../java/org/apache/shardingsphere/sharding/merge/dql/groupby/GroupByMemoryMergedResult.java b/.../java/org/apache/shardingsphere/sharding/merge/dql/groupby/GroupByMemoryMergedResult.java
@@ -30,6 +30,7 @@
 import org.apache.shardingsphere.sql.parser.binder.segment.select.projection.impl.AggregationProjection;
 import org.apache.shardingsphere.sql.parser.binder.statement.SQLStatementContext;
 import org.apache.shardingsphere.sql.parser.binder.statement.dml.SelectStatementContext;
+import org.apache.shardingsphere.sql.parser.sql.constant.AggregationType;
 import org.apache.shardingsphere.sql.parser.sql.segment.generic.table.SimpleTableSegment;
 import org.apache.shardingsphere.infra.executor.sql.QueryResult;
 import org.apache.shardingsphere.infra.merge.result.impl.memory.MemoryMergedResult;
@@ -39,6 +40,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -134,11 +136,27 @@ private boolean getValueCaseSensitiveFromTables(final QueryResult queryResult, f
         }
         return false;
     }
-    
-    private List<MemoryQueryResultRow> getMemoryResultSetRows(final SelectStatementContext selectStatementContext, 
+
+    private List<MemoryQueryResultRow> getMemoryResultSetRows(final SelectStatementContext selectStatementContext,
                                                               final Map<GroupByValue, MemoryQueryResultRow> dataMap, final List<Boolean> valueCaseSensitive) {
+        if (dataMap.isEmpty()) {
+            Object[] data = generateReturnData(selectStatementContext);
+            return Collections.singletonList(new MemoryQueryResultRow(data));
+        }
+
         List<MemoryQueryResultRow> result = new ArrayList<>(dataMap.values());
         result.sort(new GroupByRowComparator(selectStatementContext, valueCaseSensitive));
         return result;
     }
+
+    private Object[] generateReturnData(final SelectStatementContext selectStatementContext) {
+        List projections = new LinkedList(selectStatementContext.getProjectionsContext().getProjections());
+        Object[] data = new Object[projections.size()];
+        for (int i = 0; i < projections.size(); i++) {
+            if (projections.get(i) instanceof AggregationProjection && AggregationType.COUNT == ((AggregationProjection) projections.get(i)).getType()) {
+                data[i] = 0;
+            }
+        }
+        return data;
+    }
 }
diff --git a/...a/org/apache/shardingsphere/sharding/merge/dql/groupby/GroupByMemoryMergedResultTest.java b/...a/org/apache/shardingsphere/sharding/merge/dql/groupby/GroupByMemoryMergedResultTest.java
@@ -53,6 +53,7 @@ public final class GroupByMemoryMergedResultTest {
     public void assertNextForResultSetsAllEmpty() throws SQLException {
         ShardingDQLResultMerger resultMerger = new ShardingDQLResultMerger(DatabaseTypes.getActualDatabaseType("MySQL"));
         MergedResult actual = resultMerger.merge(Arrays.asList(createQueryResult(), createQueryResult(), createQueryResult()), createSelectStatementContext(), null);
+        assertTrue(actual.next());
         assertFalse(actual.next());
     }
 

diff --git a/...n/java/org/apache/shardingsphere/infra/merge/result/impl/memory/MemoryQueryResultRow.java b/...n/java/org/apache/shardingsphere/infra/merge/result/impl/memory/MemoryQueryResultRow.java
@@ -18,13 +18,15 @@
 package org.apache.shardingsphere.infra.merge.result.impl.memory;
 
 import com.google.common.base.Preconditions;
+import lombok.RequiredArgsConstructor;
 import org.apache.shardingsphere.infra.executor.sql.QueryResult;
 
 import java.sql.SQLException;
 
 /**
  * Memory query result row.
  */
+@RequiredArgsConstructor
 public final class MemoryQueryResultRow {
 
     private final Object[] data;