Fix ORDER BY with LIMIT 0

presto-main/src/main/java/com/facebook/presto/operator/TopNOperator.java

@@ -129,7 +129,7 @@ public TopNOperator(
  this.operatorContext = checkNotNull(operatorContext, "operatorContext is null");
  this.types = checkNotNull(types, "types is null");
 
- checkArgument(n > 0, "n must be greater than zero");
+ checkArgument(n >= 0, "n must be positive");
  this.n = n;
 
  this.sortTypes = checkNotNull(sortTypes, "sortTypes is null");
@@ -141,6 +141,10 @@ public TopNOperator(
  this.memoryManager = new TopNMemoryManager(checkNotNull(operatorContext, "operatorContext is null"));
 
  this.pageBuilder = new PageBuilder(types);
+
+ if (n == 0) {
+ finishing = true;
+ }
  }
 
  @Override

presto-main/src/main/java/com/facebook/presto/sql/planner/plan/TopNNode.java

@@ -47,7 +47,7 @@ public TopNNode(@JsonProperty("id") PlanNodeId id,
  super(id);
 
  Preconditions.checkNotNull(source, "source is null");
- Preconditions.checkArgument(count > 0, "count must be positive");
+ Preconditions.checkArgument(count >= 0, "count must be positive");
  Preconditions.checkNotNull(orderBy, "orderBy is null");
  Preconditions.checkArgument(!orderBy.isEmpty(), "orderBy is empty");
  Preconditions.checkArgument(orderings.size() == orderBy.size(), "orderBy and orderings sizes don't match");

presto-main/src/test/java/com/facebook/presto/operator/TestTopNOperator.java

@@ -36,6 +36,7 @@
 import static com.facebook.presto.testing.MaterializedResult.resultBuilder;
 import static io.airlift.concurrent.Threads.daemonThreadsNamed;
 import static java.util.concurrent.Executors.newCachedThreadPool;
+import static org.testng.Assert.assertEquals;
 
 @Test(singleThreaded = true)
 public class TestTopNOperator
@@ -162,4 +163,32 @@ public void testReverseOrder()
 
  assertOperatorEquals(operator, input, expected);
  }
+
+ @Test
+ public void testLimitZero()
+ throws Exception
+ {
+ List<Page> input = rowPagesBuilder(BIGINT).row(1).build();
+
+ TopNOperatorFactory factory = new TopNOperatorFactory(
+ 0,
+ ImmutableList.of(BIGINT),
+ 0,
+ ImmutableList.of(0),
+ ImmutableList.of(DESC_NULLS_LAST),
+ false);
+
+ Operator operator = factory.createOperator(driverContext);
+
+ MaterializedResult expected = resultBuilder(driverContext.getSession(), BIGINT).build();
+
+ // assertOperatorEquals assumes operators do not start in finished state
+ assertEquals(operator.isFinished(), true);
+ assertEquals(operator.needsInput(), false);
+ assertEquals(operator.getOutput(), null);
+
+ List<Page> pages = OperatorAssertion.toPages(operator, input.iterator());
+ MaterializedResult actual = OperatorAssertion.toMaterializedResult(operator.getOperatorContext().getSession(), operator.getTypes(), pages);
+ assertEquals(actual, expected);
+ }
 }

presto-tests/src/main/java/com/facebook/presto/tests/AbstractTestQueries.java

@@ -580,6 +580,13 @@ public void testLimitZero()
  assertQuery("SELECT custkey, totalprice FROM orders LIMIT 0");
  }
 
+ @Test
+ public void testOrderByLimitZero()
+ throws Exception
+ {
+ assertQuery("SELECT custkey, totalprice FROM orders ORDER BY orderkey LIMIT 0");
+ }
+
  @Test
  public void testRepeatedAggregations()
  throws Exception