From 25e3666f9823892060e8adaad8e91c1f015067af Mon Sep 17 00:00:00 2001
From: Jay <busyjaylee@gmail.com>
Date: Tue, 22 Nov 2016 21:19:30 +0800
Subject: [PATCH] copr: aggr null for first (#1339)

---
 src/server/coprocessor/aggregate.rs | 3 ---
 tests/coprocessor/test_select.rs    | 5 +++--
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/server/coprocessor/aggregate.rs b/src/server/coprocessor/aggregate.rs
index 6433754d196..e59971ca97e 100644
--- a/src/server/coprocessor/aggregate.rs
+++ b/src/server/coprocessor/aggregate.rs
@@ -61,9 +61,6 @@ impl AggrFunc for First {
         if args.len() != 1 {
             return Err(box_err!("Wrong number of args for AggFuncFirstRow: {}", args.len()));
         }
-        if args[0] == Datum::Null {
-            return Ok(());
-        }
         *self = args.pop();
         Ok(())
     }
diff --git a/tests/coprocessor/test_select.rs b/tests/coprocessor/test_select.rs
index 38e480fae2d..aa4c6dc03cd 100644
--- a/tests/coprocessor/test_select.rs
+++ b/tests/coprocessor/test_select.rs
@@ -656,6 +656,7 @@ fn test_aggr_first() {
     let data = vec![
         (1, Some("name:0"), 2),
         (2, Some("name:3"), 3),
+        (3, Some("name:5"), 3),
         (4, Some("name:0"), 1),
         (5, Some("name:5"), 4),
         (6, Some("name:5"), 4),
@@ -671,7 +672,7 @@ fn test_aggr_first() {
     let exp = vec![
         (Datum::Bytes(b"name:0".to_vec()), 1),
         (Datum::Bytes(b"name:3".to_vec()), 2),
-        (Datum::Bytes(b"name:5".to_vec()), 5),
+        (Datum::Bytes(b"name:5".to_vec()), 3),
         (Datum::Null, 7),
     ];
     let req = Select::from(&product.table).first(product.id).group_by(&[product.name]).build();
@@ -690,7 +691,7 @@ fn test_aggr_first() {
         (3, Datum::Bytes(b"name:3".to_vec())),
         (1, Datum::Bytes(b"name:0".to_vec())),
         (4, Datum::Bytes(b"name:5".to_vec())),
-        (5, Datum::Bytes(b"name:5".to_vec())),
+        (5, Datum::Null),
         (6, Datum::Null),
     ];
     let req = Select::from(&product.table).first(product.name).group_by(&[product.count]).build();