executor: fix update float panic (#8045)

executor/update.go

@@ -140,6 +140,17 @@ func (e *UpdateExec) Next(ctx context.Context, chk *chunk.Chunk) error {
 
 func (e *UpdateExec) fetchChunkRows(ctx context.Context) error {
 	fields := e.children[0].retTypes()
+	schema := e.children[0].Schema()
+	colsInfo := make([]*table.Column, len(fields))
+	for id, cols := range schema.TblID2Handle {
+		tbl := e.tblID2table[id]
+		for _, col := range cols {
+			offset := getTableOffset(schema, col)
+			for i, c := range tbl.WritableCols() {
+				colsInfo[offset+i] = c
+			}
+		}
+	}
 	globalRowIdx := 0
 	chk := e.children[0].newFirstChunk()
 	e.evalBuffer = chunk.MutRowFromTypes(fields)
@@ -156,7 +167,7 @@ func (e *UpdateExec) fetchChunkRows(ctx context.Context) error {
 		for rowIdx := 0; rowIdx < chk.NumRows(); rowIdx++ {
 			chunkRow := chk.GetRow(rowIdx)
 			datumRow := chunkRow.GetDatumRow(fields)
-			newRow, err1 := e.composeNewRow(globalRowIdx, datumRow)
+			newRow, err1 := e.composeNewRow(globalRowIdx, datumRow, colsInfo)
 			if err1 != nil {
 				return errors.Trace(err1)
 			}
@@ -181,7 +192,7 @@ func (e *UpdateExec) handleErr(colName model.CIStr, rowIdx int, err error) error
 	return errors.Trace(err)
 }
 
-func (e *UpdateExec) composeNewRow(rowIdx int, oldRow []types.Datum) ([]types.Datum, error) {
+func (e *UpdateExec) composeNewRow(rowIdx int, oldRow []types.Datum, cols []*table.Column) ([]types.Datum, error) {
 	newRowData := types.CopyRow(oldRow)
 	e.evalBuffer.SetDatums(newRowData...)
 	for _, assign := range e.OrderedList {
@@ -190,10 +201,19 @@ func (e *UpdateExec) composeNewRow(rowIdx int, oldRow []types.Datum) ([]types.Da
 			continue
 		}
 		val, err := assign.Expr.Eval(e.evalBuffer.ToRow())
+		if err = e.handleErr(assign.Col.ColName, rowIdx, err); err != nil {
+			return nil, err
+		}
 
-		if err1 := e.handleErr(assign.Col.ColName, rowIdx, err); err1 != nil {
-			return nil, err1
+		// info of `_tidb_rowid` column is nil.
+		// No need to cast `_tidb_rowid` column value.
+		if cols[assign.Col.Index] != nil {
+			val, err = table.CastValue(e.ctx, val, cols[assign.Col.Index].ColumnInfo)
+			if err = e.handleErr(assign.Col.ColName, rowIdx, err); err != nil {
+				return nil, errors.Trace(err)
+			}
 		}
+
 		newRowData[assign.Col.Index] = *val.Copy()
 		e.evalBuffer.SetDatum(assign.Col.Index, val)
 	}

executor/write_test.go

@@ -1076,6 +1076,12 @@ func (s *testSuite) TestUpdate(c *C) {
 	_, err = tk.Exec("update t, (select * from t) as b set b.k = t.k")
 	c.Assert(err.Error(), Equals, "[planner:1288]The target table b of the UPDATE is not updatable")
 	tk.MustExec("update t, (select * from t) as b set t.k = b.k")
+
+	// issue 8045
+	tk.MustExec("drop table if exists t1")
+	tk.MustExec(`CREATE TABLE t1 (c1 float)`)
+	tk.MustExec("INSERT INTO t1 SET c1 = 1")
+	tk.MustExec("UPDATE t1 SET c1 = 1.2 WHERE c1=1;")
 }
 
 func (s *testSuite) TestPartitionedTableUpdate(c *C) {