From db4a235f588976b85e2a450010d8ac3814312de3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=EA=B9=80=ED=98=95=EC=A4=80?=
 <babokim@babokim-mbp.server.gruter.com>
Date: Mon, 30 Jun 2014 19:24:27 +0900
Subject: [PATCH] TAJO-896: Full outer join query with empty intermediate data
 doesn't terminate.

---
 .../master/querymaster/Repartitioner.java     | 13 ++++++++++++
 .../tajo/engine/query/TestJoinQuery.java      | 20 +++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/tajo-core/src/main/java/org/apache/tajo/master/querymaster/Repartitioner.java b/tajo-core/src/main/java/org/apache/tajo/master/querymaster/Repartitioner.java
index 93e40fd2c8..5024211b7b 100644
--- a/tajo-core/src/main/java/org/apache/tajo/master/querymaster/Repartitioner.java
+++ b/tajo-core/src/main/java/org/apache/tajo/master/querymaster/Repartitioner.java
@@ -126,6 +126,19 @@ public static void scheduleFragmentsForJoinQuery(TaskSchedulerContext schedulerC
     // If node is outer join and a preserved relation is empty, it should return zero rows.
     joinNode = PlannerUtil.findTopNode(execBlock.getPlan(), NodeType.JOIN);
     if (joinNode != null) {
+      // If all stats art zero, return
+      boolean isAllStatsZero = true;
+      for (int i = 0; i < stats.length; i++) {
+        if (stats[i] > 0) {
+          isAllStatsZero = false;
+          break;
+        }
+      }
+      if (isAllStatsZero) {
+        LOG.info("All join target data are empty.");
+        return;
+      }
+
       // find left top scan node
       ScanNode leftScanNode = PlannerUtil.findTopNode(joinNode.getLeftChild(), NodeType.SCAN);
       ScanNode rightScanNode = PlannerUtil.findTopNode(joinNode.getRightChild(), NodeType.SCAN);
diff --git a/tajo-core/src/test/java/org/apache/tajo/engine/query/TestJoinQuery.java b/tajo-core/src/test/java/org/apache/tajo/engine/query/TestJoinQuery.java
index e109616725..8f8f86bbe8 100644
--- a/tajo-core/src/test/java/org/apache/tajo/engine/query/TestJoinQuery.java
+++ b/tajo-core/src/test/java/org/apache/tajo/engine/query/TestJoinQuery.java
@@ -1010,4 +1010,24 @@ public void testComplexJoinCondition4() throws Exception {
     assertResultSet(res);
     cleanupQuery(res);
   }
+
+  @Test
+  public void testFullOuterJoinWithEmptyIntermediateData() throws Exception {
+    ResultSet res = executeString(
+        "select a.l_orderkey \n" +
+            "from (select * from lineitem where l_orderkey < 0) a\n" +
+            "full outer join (select * from lineitem where l_orderkey < 0) b\n" +
+            "on a.l_orderkey = b.l_orderkey"
+    );
+
+    try {
+      String expected =
+          "l_orderkey\n" +
+              "-------------------------------\n";
+
+      assertEquals(expected, resultSetToString(res));
+    } finally {
+      cleanupQuery(res);
+    }
+  }
 }