infoschema: fix ddl_jobs table query column's type (#42536)

infoschema/infoschema_test.go

@@ -814,6 +814,14 @@ func TestIndexComment(t *testing.T) {
 	tk.MustQuery("SELECT index_comment,char_length(index_comment),COLUMN_NAME FROM information_schema.statistics WHERE table_name='t1' ORDER BY index_comment;").Check(testkit.Rows(" 0 c2", "i1 comment 10 c1"))
 }
 
+func TestIssue42400(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustQuery("show create table information_schema.ddl_jobs").CheckContain("`QUERY` text")
+	tk.MustQuery("select length(query) from information_schema.ddl_jobs;") // No error
+}
+
 func TestInfoSchemaRenameTable(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 

infoschema/tables.go

@@ -1213,7 +1213,7 @@ var tableDDLJobsCols = []columnInfo{
 	{name: "START_TIME", tp: mysql.TypeDatetime, size: 19},
 	{name: "END_TIME", tp: mysql.TypeDatetime, size: 19},
 	{name: "STATE", tp: mysql.TypeVarchar, size: 64},
-	{name: "QUERY", tp: mysql.TypeVarchar, size: 64},
+	{name: "QUERY", tp: mysql.TypeBlob, size: types.UnspecifiedLength},
 }
 
 var tableSequencesCols = []columnInfo{

testkit/result.go

@@ -130,3 +130,24 @@ func (res *Result) CheckAt(cols []int, expected [][]interface{}) {
 	need := fmt.Sprintf("%s", expected)
 	res.require.Equal(need, got, res.comment)
 }
+
+// CheckContain checks whether the result contains the expected string
+func (res *Result) CheckContain(expected string) {
+	var result strings.Builder
+	for i, row := range res.rows {
+		if i > 0 {
+			result.WriteString("\n")
+		}
+		for j, colValue := range row {
+			if j > 0 {
+				result.WriteString(" ")
+			}
+			result.WriteString(colValue)
+			if strings.Contains(colValue, expected) {
+				return
+			}
+		}
+	}
+	comment := fmt.Sprintf("the result doesn't contain the exepected %s\n%s", expected, result.String())
+	res.require.Equal(true, false, comment)
+}