expression: implement vectorized evaluation for builtinCastDecimalAsT…

…imeSig

expression/builtin_cast_vec.go

@@ -872,11 +872,45 @@ func (b *builtinCastDecimalAsRealSig) vecEvalReal(input *chunk.Chunk, result *ch
 }
 
 func (b *builtinCastDecimalAsTimeSig) vectorized() bool {
-	return false
+	return true
 }
 
 func (b *builtinCastDecimalAsTimeSig) vecEvalTime(input *chunk.Chunk, result *chunk.Column) error {
-	return errors.Errorf("not implemented")
+	n := input.NumRows()
+	buf, err := b.bufAllocator.get(types.ETDecimal, n)
+	if err != nil {
+		return err
+	}
+	defer b.bufAllocator.put(buf)
+	if err := b.args[0].VecEvalDecimal(b.ctx, input, buf); err != nil {
+		return err
+	}
+
+	result.ResizeTime(n, false)
+	result.MergeNulls(buf)
+	times := result.Times()
+	f64s := buf.Decimals()
+	stmt := b.ctx.GetSessionVars().StmtCtx
+	fsp := int8(b.tp.Decimal)
+	for i := 0; i < n; i++ {
+		if buf.IsNull(i) {
+			continue
+		}
+		tm, err := types.ParseTimeFromFloatString(stmt, string(f64s[i].ToString()), b.tp.Tp, fsp)
+		if err != nil {
+			if err = handleInvalidTimeError(b.ctx, err); err != nil {
+				return err
+			}
+			result.SetNull(i, true)
+			continue
+		}
+		times[i] = tm
+		if b.tp.Tp == mysql.TypeDate {
+			// Truncate hh:mm:ss part if the type is Date.
+			times[i].Time = types.FromDate(tm.Time.Year(), tm.Time.Month(), tm.Time.Day(), 0, 0, 0, 0)
+		}
+	}
+	return nil
 }
 
 func (b *builtinCastTimeAsIntSig) vectorized() bool {

expression/builtin_cast_vec_test.go

@@ -55,6 +55,7 @@ var vecBuiltinCastCases = map[string][]vecExprBenchCase{
 		{retEvalType: types.ETJson, childrenTypes: []types.EvalType{types.ETJson}},
 		{retEvalType: types.ETJson, childrenTypes: []types.EvalType{types.ETString}, geners: []dataGenerator{&jsonStringGener{}}},
 		{retEvalType: types.ETJson, childrenTypes: []types.EvalType{types.ETDecimal}},
+		{retEvalType: types.ETDatetime, childrenTypes: []types.EvalType{types.ETDecimal}},
 	},
 }