expression: enable greatest/least push down to tiflash (#32788)

close #32787
pingcap · Mar 3, 2022 · 6bc9cd3 · 6bc9cd3
1 parent 41c1cc9
commit 6bc9cd3
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Showing 2 changed files with 24 additions and 0 deletions.
diff --git a/expression/expr_to_pb_test.go b/expression/expr_to_pb_test.go
@@ -1035,6 +1035,24 @@ func TestExprPushDownToFlash(t *testing.T) {
 	require.NoError(t, err)
 	exprs = append(exprs, function)
 
+	// greatest
+	function, err = NewFunction(mock.NewContext(), ast.Greatest, types.NewFieldType(mysql.TypeLonglong), int32Column, intColumn)
+	require.NoError(t, err)
+	exprs = append(exprs, function)
+
+	function, err = NewFunction(mock.NewContext(), ast.Greatest, types.NewFieldType(mysql.TypeDouble), float32Column, intColumn)
+	require.NoError(t, err)
+	exprs = append(exprs, function)
+
+	// least
+	function, err = NewFunction(mock.NewContext(), ast.Least, types.NewFieldType(mysql.TypeLonglong), int32Column, intColumn)
+	require.NoError(t, err)
+	exprs = append(exprs, function)
+
+	function, err = NewFunction(mock.NewContext(), ast.Least, types.NewFieldType(mysql.TypeDouble), float32Column, intColumn)
+	require.NoError(t, err)
+	exprs = append(exprs, function)
+
 	pushed, remained = PushDownExprs(sc, exprs, client, kv.TiFlash)
 	require.Len(t, pushed, len(exprs))
 	require.Len(t, remained, 0)

diff --git a/expression/expression.go b/expression/expression.go
@@ -1151,6 +1151,12 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 		return true
 	case ast.Sysdate:
 		return true
+	case ast.Least, ast.Greatest:
+		switch function.Function.PbCode() {
+		case tipb.ScalarFuncSig_GreatestInt, tipb.ScalarFuncSig_GreatestReal,
+			tipb.ScalarFuncSig_LeastInt, tipb.ScalarFuncSig_LeastReal:
+			return true
+		}
 	}
 	return false
 }