rename and add tests

executor/window.go

@@ -171,6 +171,6 @@ func (e *WindowExec) copyChk(chk *chunk.Chunk) {
 	e.remainingRowsInChunk = childResult.NumRows()
 	columns := e.Schema().Columns[:len(e.Schema().Columns)-1]
 	for i, col := range columns {
-		chk.CopyColumns(childResult, i, col.Index)
+		chk.MakeRefTo(i, childResult, col.Index)
 	}
 }

util/chunk/chunk.go

@@ -138,6 +138,11 @@ func (c *Chunk) MakeRef(srcColIdx, dstColIdx int) {
 	c.columns[dstColIdx] = c.columns[srcColIdx]
 }
 
+// MakeRefTo copies columns `src.columns[srcColIdx]` to `c.columns[dstColIdx]`.
+func (c *Chunk) MakeRefTo(dstColIdx int, src *Chunk, srcColIdx int) {
+	c.columns[dstColIdx] = src.columns[srcColIdx]
+}
+
 // SwapColumn swaps column "c.columns[colIdx]" with column
 // "other.columns[otherIdx]". If there exists columns refer to the column to be
 // swapped, we need to re-build the reference.
@@ -187,11 +192,6 @@ func (c *Chunk) SwapColumns(other *Chunk) {
 	c.numVirtualRows, other.numVirtualRows = other.numVirtualRows, c.numVirtualRows
 }
 
-// CopyColumns copies columns `other.columns[from]` to `c.columns[dst]`.
-func (c *Chunk) CopyColumns(other *Chunk, dst, from int) {
-	c.columns[dst] = other.columns[from]
-}
-
 // SetNumVirtualRows sets the virtual row number for a Chunk.
 // It should only be used when there exists no column in the Chunk.
 func (c *Chunk) SetNumVirtualRows(numVirtualRows int) {

util/chunk/chunk_test.go

@@ -620,6 +620,23 @@ func (s *testChunkSuite) TestPreAlloc4RowAndInsert(c *check.C) {
 	}
 }
 
+func (s *testChunkSuite) TestMakeRefTo(c *check.C) {
+	fieldTypes := make([]*types.FieldType, 0, 2)
+	fieldTypes = append(fieldTypes, &types.FieldType{Tp: mysql.TypeFloat})
+	fieldTypes = append(fieldTypes, &types.FieldType{Tp: mysql.TypeFloat})
+
+	chk1 := NewChunkWithCapacity(fieldTypes, 1)
+	chk1.AppendFloat64(0, 1)
+	chk1.AppendFloat64(1, 3)
+
+	chk2 := NewChunkWithCapacity(fieldTypes, 1)
+	chk2.MakeRefTo(0, chk1, 1)
+	chk2.MakeRefTo(1, chk1, 0)
+
+	c.Assert(chk2.columns[0] == chk1.columns[1], check.IsTrue)
+	c.Assert(chk2.columns[1] == chk1.columns[0], check.IsTrue)
+}
+
 func BenchmarkAppendInt(b *testing.B) {
 	b.ReportAllocs()
 	chk := newChunk(8)