http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithEmptyTable5.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithEmptyTable5.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithEmptyTable5.Sort_NoBroadcast.plan
index 99b7def..5e32a29 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithEmptyTable5.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithEmptyTable5.Sort_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.lineitem.l_linenumber (INT4) (asc)
+  => Sort Keys: default.lineitem.l_linenumber (INT4) (asc, nulls last)
    GROUP_BY(3)(l_linenumber)
      => exprs: (sum(default.empty_orders.o_orderkey 
(INT4)),max(default.empty_orders.o_orderstatus 
(TEXT)),max(default.empty_orders.o_orderdate 
(TEXT)),avg(default.lineitem.l_quantity 
(FLOAT8)),sum(default.lineitem.l_quantity (FLOAT8)))
      => target list: default.lineitem.l_linenumber (INT4), ?sum (INT8), ?max_1 
(TEXT), ?max_2 (TEXT), ?avg_3 (FLOAT8), ?sum_4 (FLOAT8)
@@ -105,7 +105,7 @@ Block Id: eb_0000000000000_0000_000004 [INTERMEDIATE]
 [q_0000000000000_0000] 4 => 5 (type=RANGE_SHUFFLE, 
key=default.lineitem.l_linenumber (INT4), num=32)
 
 SORT(13)
-  => Sort Keys: default.lineitem.l_linenumber (INT4) (asc)
+  => Sort Keys: default.lineitem.l_linenumber (INT4) (asc, nulls last)
    GROUP_BY(3)(l_linenumber)
      => exprs: (sum(?sum_7 (INT8)),max(?max_8 (TEXT)),max(?max_9 
(TEXT)),avg(?avg_10 (PROTOBUF)),sum(?sum_11 (FLOAT8)))
      => target list: default.lineitem.l_linenumber (INT4), ?sum (INT8), ?max_1 
(TEXT), ?max_2 (TEXT), ?avg_3 (FLOAT8), ?sum_4 (FLOAT8)
@@ -126,7 +126,7 @@ Block Id: eb_0000000000000_0000_000005 [ROOT]
  0: sorted input=eb_0000000000000_0000_000004
 
 SORT(4)
-  => Sort Keys: default.lineitem.l_linenumber (INT4) (asc)
+  => Sort Keys: default.lineitem.l_linenumber (INT4) (asc, nulls last)
    SCAN(14) on eb_0000000000000_0000_000004
      => out schema: {(6) ?avg_3 (FLOAT8), ?max_1 (TEXT), ?max_2 (TEXT), ?sum 
(INT8), ?sum_4 (FLOAT8), default.lineitem.l_linenumber (INT4)}
      => in schema: {(6) ?avg_3 (FLOAT8), ?max_1 (TEXT), ?max_2 (TEXT), ?sum 
(INT8), ?sum_4 (FLOAT8), default.lineitem.l_linenumber (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash.plan
index 4de481f..074245f 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) IS NULL
       JOIN(7)(LEFT_OUTER)
@@ -44,7 +44,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) IS NULL
       JOIN(7)(LEFT_OUTER)
@@ -72,7 +72,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash_NoBroadcast.plan
index 5fa4bd8..2ce8bed 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Hash_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) IS NULL
       JOIN(7)(LEFT_OUTER)
@@ -73,7 +73,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.orders.o_orderkey (INT4), num=32)
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) IS NULL
       JOIN(7)(LEFT_OUTER)
@@ -99,7 +99,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort.plan
index 4de481f..074245f 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) IS NULL
       JOIN(7)(LEFT_OUTER)
@@ -44,7 +44,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) IS NULL
       JOIN(7)(LEFT_OUTER)
@@ -72,7 +72,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort_NoBroadcast.plan
index 5fa4bd8..2ce8bed 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull1.Sort_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) IS NULL
       JOIN(7)(LEFT_OUTER)
@@ -73,7 +73,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.orders.o_orderkey (INT4), num=32)
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) IS NULL
       JOIN(7)(LEFT_OUTER)
@@ -99,7 +99,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash.plan
index a8638e7..28c69e2 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: (default.orders.o_orderdate (TEXT) IS NOT NULL AND 
default.orders.o_orderdate (TEXT)LIKE'1996%')
       JOIN(7)(LEFT_OUTER)
@@ -44,7 +44,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: (default.orders.o_orderdate (TEXT) IS NOT NULL AND 
default.orders.o_orderdate (TEXT)LIKE'1996%')
       JOIN(7)(LEFT_OUTER)
@@ -72,7 +72,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash_NoBroadcast.plan
index f5b1292..df7b416 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Hash_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: (default.orders.o_orderdate (TEXT) IS NOT NULL AND 
default.orders.o_orderdate (TEXT)LIKE'1996%')
       JOIN(7)(LEFT_OUTER)
@@ -73,7 +73,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.orders.o_orderkey (INT4), num=32)
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: (default.orders.o_orderdate (TEXT) IS NOT NULL AND 
default.orders.o_orderdate (TEXT)LIKE'1996%')
       JOIN(7)(LEFT_OUTER)
@@ -99,7 +99,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort.plan
index a8638e7..28c69e2 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: (default.orders.o_orderdate (TEXT) IS NOT NULL AND 
default.orders.o_orderdate (TEXT)LIKE'1996%')
       JOIN(7)(LEFT_OUTER)
@@ -44,7 +44,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: (default.orders.o_orderdate (TEXT) IS NOT NULL AND 
default.orders.o_orderdate (TEXT)LIKE'1996%')
       JOIN(7)(LEFT_OUTER)
@@ -72,7 +72,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort_NoBroadcast.plan
index f5b1292..df7b416 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull2.Sort_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: (default.orders.o_orderdate (TEXT) IS NOT NULL AND 
default.orders.o_orderdate (TEXT)LIKE'1996%')
       JOIN(7)(LEFT_OUTER)
@@ -73,7 +73,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.orders.o_orderkey (INT4), num=32)
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: (default.orders.o_orderdate (TEXT) IS NOT NULL AND 
default.orders.o_orderdate (TEXT)LIKE'1996%')
       JOIN(7)(LEFT_OUTER)
@@ -99,7 +99,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash.plan
index 5bace36..27fa16f 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) = 100
       JOIN(7)(LEFT_OUTER)
@@ -44,7 +44,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) = 100
       JOIN(7)(LEFT_OUTER)
@@ -72,7 +72,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash_NoBroadcast.plan
index bf3ec17..27f7335 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Hash_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) = 100
       JOIN(7)(LEFT_OUTER)
@@ -73,7 +73,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.orders.o_orderkey (INT4), num=32)
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) = 100
       JOIN(7)(LEFT_OUTER)
@@ -99,7 +99,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort.plan
index 5bace36..27fa16f 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) = 100
       JOIN(7)(LEFT_OUTER)
@@ -44,7 +44,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) = 100
       JOIN(7)(LEFT_OUTER)
@@ -72,7 +72,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort_NoBroadcast.plan
index bf3ec17..27f7335 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testLeftOuterJoinWithNull3.Sort_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) = 100
       JOIN(7)(LEFT_OUTER)
@@ -73,7 +73,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.orders.o_orderkey (INT4), num=32)
 
 SORT(11)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SELECTION(3)
      => Search Cond: default.orders.o_orderkey (INT4) = 100
       JOIN(7)(LEFT_OUTER)
@@ -99,7 +99,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(4)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(12) on eb_0000000000000_0000_000003
      => out schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}
      => in schema: {(4) ?coalesce (TEXT), default.customer.c_custkey (INT4), 
default.orders.o_orderdate (TEXT), default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash.plan
index cbb8253..43fc9f7 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(5)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: CASE WHEN default.b.name (TEXT) IS NULL THEN 9991231 ELSE 
default.b.name (TEXT) END as c1, CASE WHEN default.c.name (TEXT) IS NULL THEN 
9991231 ELSE default.c.name (TEXT) END as c2, default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)
@@ -52,7 +52,7 @@ Block Id: eb_0000000000000_0000_000005 [LEAF]
  1: type=Broadcast, tables=default.c
 
 SORT(15)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: CASE WHEN default.b.name (TEXT) IS NULL THEN 9991231 ELSE 
default.b.name (TEXT) END as c1, CASE WHEN default.c.name (TEXT) IS NULL THEN 
9991231 ELSE default.c.name (TEXT) END as c2, default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)
@@ -87,7 +87,7 @@ Block Id: eb_0000000000000_0000_000006 [ROOT]
  0: sorted input=eb_0000000000000_0000_000005
 
 SORT(5)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    SCAN(16) on eb_0000000000000_0000_000005
      => out schema: {(6) c1 (TEXT), c2 (TEXT), default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)}
      => in schema: {(6) c1 (TEXT), c2 (TEXT), default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash_NoBroadcast.plan
index 02d893c..749c8c0 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Hash_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(5)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: CASE WHEN default.b.name (TEXT) IS NULL THEN 9991231 ELSE 
default.b.name (TEXT) END as c1, CASE WHEN default.c.name (TEXT) IS NULL THEN 
9991231 ELSE default.c.name (TEXT) END as c2, default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)
@@ -119,7 +119,7 @@ Block Id: eb_0000000000000_0000_000005 [INTERMEDIATE]
 [q_0000000000000_0000] 5 => 6 (type=RANGE_SHUFFLE, key=default.a.id (INT4), 
default.a.name (TEXT), num=32)
 
 SORT(15)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: CASE WHEN default.b.name (TEXT) IS NULL THEN 9991231 ELSE 
default.b.name (TEXT) END as c1, CASE WHEN default.c.name (TEXT) IS NULL THEN 
9991231 ELSE default.c.name (TEXT) END as c2, default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)
@@ -143,7 +143,7 @@ Block Id: eb_0000000000000_0000_000006 [ROOT]
  0: sorted input=eb_0000000000000_0000_000005
 
 SORT(5)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    SCAN(16) on eb_0000000000000_0000_000005
      => out schema: {(6) c1 (TEXT), c2 (TEXT), default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)}
      => in schema: {(6) c1 (TEXT), c2 (TEXT), default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort.plan
index cbb8253..43fc9f7 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(5)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: CASE WHEN default.b.name (TEXT) IS NULL THEN 9991231 ELSE 
default.b.name (TEXT) END as c1, CASE WHEN default.c.name (TEXT) IS NULL THEN 
9991231 ELSE default.c.name (TEXT) END as c2, default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)
@@ -52,7 +52,7 @@ Block Id: eb_0000000000000_0000_000005 [LEAF]
  1: type=Broadcast, tables=default.c
 
 SORT(15)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: CASE WHEN default.b.name (TEXT) IS NULL THEN 9991231 ELSE 
default.b.name (TEXT) END as c1, CASE WHEN default.c.name (TEXT) IS NULL THEN 
9991231 ELSE default.c.name (TEXT) END as c2, default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)
@@ -87,7 +87,7 @@ Block Id: eb_0000000000000_0000_000006 [ROOT]
  0: sorted input=eb_0000000000000_0000_000005
 
 SORT(5)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    SCAN(16) on eb_0000000000000_0000_000005
      => out schema: {(6) c1 (TEXT), c2 (TEXT), default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)}
      => in schema: {(6) c1 (TEXT), c2 (TEXT), default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort_NoBroadcast.plan
index 02d893c..749c8c0 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testOuterJoinAndCaseWhen1.Sort_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(5)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: CASE WHEN default.b.name (TEXT) IS NULL THEN 9991231 ELSE 
default.b.name (TEXT) END as c1, CASE WHEN default.c.name (TEXT) IS NULL THEN 
9991231 ELSE default.c.name (TEXT) END as c2, default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)
@@ -119,7 +119,7 @@ Block Id: eb_0000000000000_0000_000005 [INTERMEDIATE]
 [q_0000000000000_0000] 5 => 6 (type=RANGE_SHUFFLE, key=default.a.id (INT4), 
default.a.name (TEXT), num=32)
 
 SORT(15)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: CASE WHEN default.b.name (TEXT) IS NULL THEN 9991231 ELSE 
default.b.name (TEXT) END as c1, CASE WHEN default.c.name (TEXT) IS NULL THEN 
9991231 ELSE default.c.name (TEXT) END as c2, default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)
@@ -143,7 +143,7 @@ Block Id: eb_0000000000000_0000_000006 [ROOT]
  0: sorted input=eb_0000000000000_0000_000005
 
 SORT(5)
-  => Sort Keys: default.a.id (INT4) (asc),default.a.name (TEXT) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last),default.a.name (TEXT) 
(asc, nulls last)
    SCAN(16) on eb_0000000000000_0000_000005
      => out schema: {(6) c1 (TEXT), c2 (TEXT), default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)}
      => in schema: {(6) c1 (TEXT), c2 (TEXT), default.a.id (INT4), 
default.a.name (TEXT), id2 (INT4), name2 (TEXT)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash.plan
index 70507fe..66c22df 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)
@@ -42,7 +42,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(10)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)
@@ -68,7 +68,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(11) on eb_0000000000000_0000_000003
      => out schema: {(2) default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)}
      => in schema: {(2) default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash_NoBroadcast.plan
index dbf2979..c421b35 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Hash_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)
@@ -71,7 +71,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.orders.o_orderkey (INT4), num=32)
 
 SORT(10)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)
@@ -95,7 +95,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(11) on eb_0000000000000_0000_000003
      => out schema: {(2) default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)}
      => in schema: {(2) default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort.plan
index 70507fe..66c22df 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)
@@ -42,7 +42,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(10)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)
@@ -68,7 +68,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(11) on eb_0000000000000_0000_000003
      => out schema: {(2) default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)}
      => in schema: {(2) default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort_NoBroadcast.plan
index dbf2979..c421b35 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoin1.Sort_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)
@@ -71,7 +71,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.orders.o_orderkey (INT4), num=32)
 
 SORT(10)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)
@@ -95,7 +95,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(11) on eb_0000000000000_0000_000003
      => out schema: {(2) default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)}
      => in schema: {(2) default.customer.c_custkey (INT4), 
default.orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash.plan
index b271dcc..9993ecf 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.empty_orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)
@@ -42,7 +42,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.empty_orders
 
 SORT(10)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.empty_orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)
@@ -68,7 +68,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(11) on eb_0000000000000_0000_000003
      => out schema: {(2) default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)}
      => in schema: {(2) default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash_NoBroadcast.plan
index 199c70c..bccf72c 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Hash_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.empty_orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)
@@ -71,7 +71,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.empty_orders.o_orderkey (INT4), 
num=32)
 
 SORT(10)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.empty_orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)
@@ -95,7 +95,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(11) on eb_0000000000000_0000_000003
      => out schema: {(2) default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)}
      => in schema: {(2) default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort.plan
index b271dcc..9993ecf 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.empty_orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)
@@ -42,7 +42,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.empty_orders
 
 SORT(10)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.empty_orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)
@@ -68,7 +68,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(11) on eb_0000000000000_0000_000003
      => out schema: {(2) default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)}
      => in schema: {(2) default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort_NoBroadcast.plan
index 199c70c..bccf72c 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinQuery/testRightOuterJoinWithEmptyTable1.Sort_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.empty_orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)
@@ -71,7 +71,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.empty_orders.o_orderkey (INT4), 
num=32)
 
 SORT(10)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    JOIN(6)(RIGHT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = 
default.empty_orders.o_orderkey (INT4)
      => target list: default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)
@@ -95,7 +95,7 @@ Block Id: eb_0000000000000_0000_000004 [ROOT]
  0: sorted input=eb_0000000000000_0000_000003
 
 SORT(3)
-  => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.empty_orders.o_orderkey (INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.empty_orders.o_orderkey (INT4) (asc, nulls last)
    SCAN(11) on eb_0000000000000_0000_000003
      => out schema: {(2) default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)}
      => in schema: {(2) default.customer.c_custkey (INT4), 
default.empty_orders.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash.plan
index 4fb9de0..dffcecb 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash.plan
@@ -5,7 +5,7 @@ PROJECTION(6)
   => out schema: {(3) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4), val (TEXT)}
   => in  schema: {(2) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)}
    SORT(5)
-     => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.o.o_orderkey (INT4) (asc)
+     => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
       JOIN(8)(LEFT_OUTER)
         => Join Cond: default.customer.c_custkey (INT4) = default.o.o_orderkey 
(INT4)
         => target list: default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)
@@ -50,7 +50,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(12)
-  => Sort Keys: default.customer.c_custkey (INT4) (asc),default.o.o_orderkey 
(INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
    JOIN(8)(LEFT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = default.o.o_orderkey 
(INT4)
      => target list: default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)
@@ -88,7 +88,7 @@ PROJECTION(6)
   => out schema: {(3) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4), val (TEXT)}
   => in  schema: {(2) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)}
    SORT(5)
-     => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.o.o_orderkey (INT4) (asc)
+     => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
       SCAN(13) on eb_0000000000000_0000_000003
         => out schema: {(2) default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)}
         => in schema: {(2) default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash_NoBroadcast.plan
index e4156aa..6ee78dd 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Hash_NoBroadcast.plan
@@ -5,7 +5,7 @@ PROJECTION(6)
   => out schema: {(3) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4), val (TEXT)}
   => in  schema: {(2) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)}
    SORT(5)
-     => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.o.o_orderkey (INT4) (asc)
+     => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
       JOIN(8)(LEFT_OUTER)
         => Join Cond: default.customer.c_custkey (INT4) = default.o.o_orderkey 
(INT4)
         => target list: default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)
@@ -87,7 +87,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.o.o_orderkey (INT4), num=32)
 
 SORT(12)
-  => Sort Keys: default.customer.c_custkey (INT4) (asc),default.o.o_orderkey 
(INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
    JOIN(8)(LEFT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = default.o.o_orderkey 
(INT4)
      => target list: default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)
@@ -115,7 +115,7 @@ PROJECTION(6)
   => out schema: {(3) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4), val (TEXT)}
   => in  schema: {(2) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)}
    SORT(5)
-     => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.o.o_orderkey (INT4) (asc)
+     => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
       SCAN(13) on eb_0000000000000_0000_000003
         => out schema: {(2) default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)}
         => in schema: {(2) default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort.plan
index 4fb9de0..dffcecb 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort.plan
@@ -5,7 +5,7 @@ PROJECTION(6)
   => out schema: {(3) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4), val (TEXT)}
   => in  schema: {(2) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)}
    SORT(5)
-     => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.o.o_orderkey (INT4) (asc)
+     => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
       JOIN(8)(LEFT_OUTER)
         => Join Cond: default.customer.c_custkey (INT4) = default.o.o_orderkey 
(INT4)
         => target list: default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)
@@ -50,7 +50,7 @@ Block Id: eb_0000000000000_0000_000003 [LEAF]
  0: type=Broadcast, tables=default.orders
 
 SORT(12)
-  => Sort Keys: default.customer.c_custkey (INT4) (asc),default.o.o_orderkey 
(INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
    JOIN(8)(LEFT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = default.o.o_orderkey 
(INT4)
      => target list: default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)
@@ -88,7 +88,7 @@ PROJECTION(6)
   => out schema: {(3) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4), val (TEXT)}
   => in  schema: {(2) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)}
    SORT(5)
-     => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.o.o_orderkey (INT4) (asc)
+     => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
       SCAN(13) on eb_0000000000000_0000_000003
         => out schema: {(2) default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)}
         => in schema: {(2) default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort_NoBroadcast.plan
index e4156aa..6ee78dd 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr2.Sort_NoBroadcast.plan
@@ -5,7 +5,7 @@ PROJECTION(6)
   => out schema: {(3) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4), val (TEXT)}
   => in  schema: {(2) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)}
    SORT(5)
-     => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.o.o_orderkey (INT4) (asc)
+     => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
       JOIN(8)(LEFT_OUTER)
         => Join Cond: default.customer.c_custkey (INT4) = default.o.o_orderkey 
(INT4)
         => target list: default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)
@@ -87,7 +87,7 @@ Block Id: eb_0000000000000_0000_000003 [INTERMEDIATE]
 [q_0000000000000_0000] 3 => 4 (type=RANGE_SHUFFLE, 
key=default.customer.c_custkey (INT4), default.o.o_orderkey (INT4), num=32)
 
 SORT(12)
-  => Sort Keys: default.customer.c_custkey (INT4) (asc),default.o.o_orderkey 
(INT4) (asc)
+  => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
    JOIN(8)(LEFT_OUTER)
      => Join Cond: default.customer.c_custkey (INT4) = default.o.o_orderkey 
(INT4)
      => target list: default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)
@@ -115,7 +115,7 @@ PROJECTION(6)
   => out schema: {(3) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4), val (TEXT)}
   => in  schema: {(2) default.customer.c_custkey (INT4), default.o.o_orderkey 
(INT4)}
    SORT(5)
-     => Sort Keys: default.customer.c_custkey (INT4) 
(asc),default.o.o_orderkey (INT4) (asc)
+     => Sort Keys: default.customer.c_custkey (INT4) (asc, nulls 
last),default.o.o_orderkey (INT4) (asc, nulls last)
       SCAN(13) on eb_0000000000000_0000_000003
         => out schema: {(2) default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)}
         => in schema: {(2) default.customer.c_custkey (INT4), 
default.o.o_orderkey (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash.plan
index 0fe36c0..52bec4b 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash.plan
@@ -5,7 +5,7 @@ PROJECTION(7)
   => out schema: {(3) const_val (INT8), default.a.c_custkey (INT4), 
default.b.min_name (TEXT)}
   => in  schema: {(2) default.a.c_custkey (INT4), default.b.min_name (TEXT)}
    SORT(6)
-     => Sort Keys: default.a.c_custkey (INT4) (asc)
+     => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
       JOIN(9)(LEFT_OUTER)
         => Join Cond: default.a.c_custkey (INT4) = default.b.c_custkey (INT4)
         => target list: default.a.c_custkey (INT4), default.b.min_name (TEXT)
@@ -118,7 +118,7 @@ Block Id: eb_0000000000000_0000_000004 [INTERMEDIATE]
 [q_0000000000000_0000] 4 => 5 (type=RANGE_SHUFFLE, key=default.a.c_custkey 
(INT4), num=32)
 
 SORT(15)
-  => Sort Keys: default.a.c_custkey (INT4) (asc)
+  => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.c_custkey (INT4) = default.b.c_custkey (INT4)
      => target list: default.a.c_custkey (INT4), default.b.min_name (TEXT)
@@ -146,7 +146,7 @@ PROJECTION(7)
   => out schema: {(3) const_val (INT8), default.a.c_custkey (INT4), 
default.b.min_name (TEXT)}
   => in  schema: {(2) default.a.c_custkey (INT4), default.b.min_name (TEXT)}
    SORT(6)
-     => Sort Keys: default.a.c_custkey (INT4) (asc)
+     => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
       SCAN(16) on eb_0000000000000_0000_000004
         => out schema: {(2) default.a.c_custkey (INT4), default.b.min_name 
(TEXT)}
         => in schema: {(2) default.a.c_custkey (INT4), default.b.min_name 
(TEXT)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash_NoBroadcast.plan
index 0fe36c0..52bec4b 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Hash_NoBroadcast.plan
@@ -5,7 +5,7 @@ PROJECTION(7)
   => out schema: {(3) const_val (INT8), default.a.c_custkey (INT4), 
default.b.min_name (TEXT)}
   => in  schema: {(2) default.a.c_custkey (INT4), default.b.min_name (TEXT)}
    SORT(6)
-     => Sort Keys: default.a.c_custkey (INT4) (asc)
+     => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
       JOIN(9)(LEFT_OUTER)
         => Join Cond: default.a.c_custkey (INT4) = default.b.c_custkey (INT4)
         => target list: default.a.c_custkey (INT4), default.b.min_name (TEXT)
@@ -118,7 +118,7 @@ Block Id: eb_0000000000000_0000_000004 [INTERMEDIATE]
 [q_0000000000000_0000] 4 => 5 (type=RANGE_SHUFFLE, key=default.a.c_custkey 
(INT4), num=32)
 
 SORT(15)
-  => Sort Keys: default.a.c_custkey (INT4) (asc)
+  => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.c_custkey (INT4) = default.b.c_custkey (INT4)
      => target list: default.a.c_custkey (INT4), default.b.min_name (TEXT)
@@ -146,7 +146,7 @@ PROJECTION(7)
   => out schema: {(3) const_val (INT8), default.a.c_custkey (INT4), 
default.b.min_name (TEXT)}
   => in  schema: {(2) default.a.c_custkey (INT4), default.b.min_name (TEXT)}
    SORT(6)
-     => Sort Keys: default.a.c_custkey (INT4) (asc)
+     => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
       SCAN(16) on eb_0000000000000_0000_000004
         => out schema: {(2) default.a.c_custkey (INT4), default.b.min_name 
(TEXT)}
         => in schema: {(2) default.a.c_custkey (INT4), default.b.min_name 
(TEXT)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort.plan
index 0fe36c0..52bec4b 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort.plan
@@ -5,7 +5,7 @@ PROJECTION(7)
   => out schema: {(3) const_val (INT8), default.a.c_custkey (INT4), 
default.b.min_name (TEXT)}
   => in  schema: {(2) default.a.c_custkey (INT4), default.b.min_name (TEXT)}
    SORT(6)
-     => Sort Keys: default.a.c_custkey (INT4) (asc)
+     => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
       JOIN(9)(LEFT_OUTER)
         => Join Cond: default.a.c_custkey (INT4) = default.b.c_custkey (INT4)
         => target list: default.a.c_custkey (INT4), default.b.min_name (TEXT)
@@ -118,7 +118,7 @@ Block Id: eb_0000000000000_0000_000004 [INTERMEDIATE]
 [q_0000000000000_0000] 4 => 5 (type=RANGE_SHUFFLE, key=default.a.c_custkey 
(INT4), num=32)
 
 SORT(15)
-  => Sort Keys: default.a.c_custkey (INT4) (asc)
+  => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.c_custkey (INT4) = default.b.c_custkey (INT4)
      => target list: default.a.c_custkey (INT4), default.b.min_name (TEXT)
@@ -146,7 +146,7 @@ PROJECTION(7)
   => out schema: {(3) const_val (INT8), default.a.c_custkey (INT4), 
default.b.min_name (TEXT)}
   => in  schema: {(2) default.a.c_custkey (INT4), default.b.min_name (TEXT)}
    SORT(6)
-     => Sort Keys: default.a.c_custkey (INT4) (asc)
+     => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
       SCAN(16) on eb_0000000000000_0000_000004
         => out schema: {(2) default.a.c_custkey (INT4), default.b.min_name 
(TEXT)}
         => in schema: {(2) default.a.c_custkey (INT4), default.b.min_name 
(TEXT)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort_NoBroadcast.plan
index 0fe36c0..52bec4b 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithConstantExpr3.Sort_NoBroadcast.plan
@@ -5,7 +5,7 @@ PROJECTION(7)
   => out schema: {(3) const_val (INT8), default.a.c_custkey (INT4), 
default.b.min_name (TEXT)}
   => in  schema: {(2) default.a.c_custkey (INT4), default.b.min_name (TEXT)}
    SORT(6)
-     => Sort Keys: default.a.c_custkey (INT4) (asc)
+     => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
       JOIN(9)(LEFT_OUTER)
         => Join Cond: default.a.c_custkey (INT4) = default.b.c_custkey (INT4)
         => target list: default.a.c_custkey (INT4), default.b.min_name (TEXT)
@@ -118,7 +118,7 @@ Block Id: eb_0000000000000_0000_000004 [INTERMEDIATE]
 [q_0000000000000_0000] 4 => 5 (type=RANGE_SHUFFLE, key=default.a.c_custkey 
(INT4), num=32)
 
 SORT(15)
-  => Sort Keys: default.a.c_custkey (INT4) (asc)
+  => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
    JOIN(9)(LEFT_OUTER)
      => Join Cond: default.a.c_custkey (INT4) = default.b.c_custkey (INT4)
      => target list: default.a.c_custkey (INT4), default.b.min_name (TEXT)
@@ -146,7 +146,7 @@ PROJECTION(7)
   => out schema: {(3) const_val (INT8), default.a.c_custkey (INT4), 
default.b.min_name (TEXT)}
   => in  schema: {(2) default.a.c_custkey (INT4), default.b.min_name (TEXT)}
    SORT(6)
-     => Sort Keys: default.a.c_custkey (INT4) (asc)
+     => Sort Keys: default.a.c_custkey (INT4) (asc, nulls last)
       SCAN(16) on eb_0000000000000_0000_000004
         => out schema: {(2) default.a.c_custkey (INT4), default.b.min_name 
(TEXT)}
         => in schema: {(2) default.a.c_custkey (INT4), default.b.min_name 
(TEXT)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash.plan
index 2e0cc87..e800b21 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(7)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    JOIN(11)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: default.a.id (INT4), default.b.id (INT4)
@@ -57,7 +57,7 @@ Block Id: eb_0000000000000_0000_000005 [LEAF]
  1: type=Broadcast, tables=default.lineitem
 
 SORT(17)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    JOIN(11)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: default.a.id (INT4), default.b.id (INT4)
@@ -101,7 +101,7 @@ Block Id: eb_0000000000000_0000_000006 [ROOT]
  0: sorted input=eb_0000000000000_0000_000005
 
 SORT(7)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    SCAN(18) on eb_0000000000000_0000_000005
      => out schema: {(2) default.a.id (INT4), default.b.id (INT4)}
      => in schema: {(2) default.a.id (INT4), default.b.id (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash_NoBroadcast.plan
index 703f32c..527c378 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Hash_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(7)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    JOIN(11)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: default.a.id (INT4), default.b.id (INT4)
@@ -133,7 +133,7 @@ Block Id: eb_0000000000000_0000_000005 [INTERMEDIATE]
 [q_0000000000000_0000] 5 => 6 (type=RANGE_SHUFFLE, key=default.a.id (INT4), 
num=32)
 
 SORT(17)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    JOIN(11)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: default.a.id (INT4), default.b.id (INT4)
@@ -157,7 +157,7 @@ Block Id: eb_0000000000000_0000_000006 [ROOT]
  0: sorted input=eb_0000000000000_0000_000005
 
 SORT(7)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    SCAN(18) on eb_0000000000000_0000_000005
      => out schema: {(2) default.a.id (INT4), default.b.id (INT4)}
      => in schema: {(2) default.a.id (INT4), default.b.id (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort.plan
index 2e0cc87..e800b21 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(7)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    JOIN(11)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: default.a.id (INT4), default.b.id (INT4)
@@ -57,7 +57,7 @@ Block Id: eb_0000000000000_0000_000005 [LEAF]
  1: type=Broadcast, tables=default.lineitem
 
 SORT(17)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    JOIN(11)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: default.a.id (INT4), default.b.id (INT4)
@@ -101,7 +101,7 @@ Block Id: eb_0000000000000_0000_000006 [ROOT]
  0: sorted input=eb_0000000000000_0000_000005
 
 SORT(7)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    SCAN(18) on eb_0000000000000_0000_000005
      => out schema: {(2) default.a.id (INT4), default.b.id (INT4)}
      => in schema: {(2) default.a.id (INT4), default.b.id (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort_NoBroadcast.plan
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort_NoBroadcast.plan
 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort_NoBroadcast.plan
index 703f32c..527c378 100644
--- 
a/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort_NoBroadcast.plan
+++ 
b/tajo-core-tests/src/test/resources/results/TestOuterJoinWithSubQuery/testLeftOuterJoinWithEmptySubquery1.1.Sort_NoBroadcast.plan
@@ -1,7 +1,7 @@
 explain
 -------------------------------
 SORT(7)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    JOIN(11)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: default.a.id (INT4), default.b.id (INT4)
@@ -133,7 +133,7 @@ Block Id: eb_0000000000000_0000_000005 [INTERMEDIATE]
 [q_0000000000000_0000] 5 => 6 (type=RANGE_SHUFFLE, key=default.a.id (INT4), 
num=32)
 
 SORT(17)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    JOIN(11)(LEFT_OUTER)
      => Join Cond: default.a.id (INT4) = default.b.id (INT4)
      => target list: default.a.id (INT4), default.b.id (INT4)
@@ -157,7 +157,7 @@ Block Id: eb_0000000000000_0000_000006 [ROOT]
  0: sorted input=eb_0000000000000_0000_000005
 
 SORT(7)
-  => Sort Keys: default.a.id (INT4) (asc)
+  => Sort Keys: default.a.id (INT4) (asc, nulls last)
    SCAN(18) on eb_0000000000000_0000_000005
      => out schema: {(2) default.a.id (INT4), default.b.id (INT4)}
      => in schema: {(2) default.a.id (INT4), default.b.id (INT4)}

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window4.result
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window4.result 
b/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window4.result
index 45ccdcc..680ee76 100644
--- a/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window4.result
+++ b/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window4.result
@@ -17,8 +17,7 @@
                 "ColumnName": "dt",
                 "OpType": "Column"
               },
-              "IsAsc": true,
-              "IsNullFirst": false
+              "IsAsc": true
             }
           ]
         },

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window5.result
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window5.result 
b/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window5.result
index aa00a09..035e831 100644
--- a/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window5.result
+++ b/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window5.result
@@ -47,7 +47,7 @@
                 "OpType": "Function"
               },
               "IsAsc": true,
-              "IsNullFirst": false
+              "IsNullsFirst": false
             }
           ]
         },

http://git-wip-us.apache.org/repos/asf/tajo/blob/8209e4c8/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window6.result
----------------------------------------------------------------------
diff --git 
a/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window6.result 
b/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window6.result
index 2c990c6..1c3fb4f 100644
--- a/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window6.result
+++ b/tajo-core-tests/src/test/resources/results/TestSQLAnalyzer/window6.result
@@ -47,7 +47,7 @@
                 "OpType": "Function"
               },
               "IsAsc": true,
-              "IsNullFirst": false
+              "IsNullsFirst": false
             }
           ],
           "windowFrame": {

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