func (s *testEvaluatorSuite) TestEvaluatedFlag(c *C) {
l := ast.NewValueExpr(int64(1))
r := ast.NewValueExpr(int64(2))
b := &ast.BinaryOperationExpr{L: l, R: r, Op: opcode.Plus}
ast.SetFlag(b)
c.Assert(ast.IsPreEvaluable(b), Equals, true)
d, err := Eval(s.ctx, b)
c.Assert(ast.IsEvaluated(b), Equals, true)
c.Assert(err, IsNil)
c.Assert(d, testutil.DatumEquals, types.NewIntDatum(3))
funcCall := &ast.FuncCallExpr{
FnName: model.NewCIStr("abs"),
Args: []ast.ExprNode{ast.NewValueExpr(int(-1))},
}
b = &ast.BinaryOperationExpr{L: funcCall, R: r, Op: opcode.Plus}
ast.ResetEvaluatedFlag(b)
ast.SetFlag(b)
c.Assert(ast.IsPreEvaluable(b), Equals, true)
d, err = Eval(s.ctx, b)
c.Assert(ast.IsEvaluated(b), Equals, false)
c.Assert(err, IsNil)
c.Assert(d, testutil.DatumEquals, types.NewIntDatum(3))
rf := &ast.ResultField{Expr: ast.NewValueExpr(int64(1))}
colExpr := &ast.ColumnNameExpr{Refer: rf}
b = &ast.BinaryOperationExpr{L: colExpr, R: r, Op: opcode.Plus}
ast.ResetEvaluatedFlag(b)
ast.SetFlag(b)
c.Assert(ast.IsPreEvaluable(b), Equals, false)
d, err = Eval(s.ctx, b)
c.Assert(ast.IsEvaluated(b), Equals, false)
c.Assert(err, IsNil)
c.Assert(d, testutil.DatumEquals, types.NewIntDatum(3))
}
// Eval evaluates an expression to a datum.
func Eval(ctx context.Context, expr ast.ExprNode) (d types.Datum, err error) {
if ast.IsEvaluated(expr) {
return *expr.GetDatum(), nil
}
e := &Evaluator{ctx: ctx}
expr.Accept(e)
if e.err != nil {
return d, errors.Trace(e.err)
}
if ast.IsPreEvaluable(expr) && (expr.GetFlag()&ast.FlagHasFunc == 0) {
expr.SetFlag(expr.GetFlag() | ast.FlagPreEvaluated)
}
return *expr.GetDatum(), nil
}