infoschema: fix bug of column size of set and enum type (#7347)

Author: Lingyu Song

infoschema/tables.go

@@ -797,6 +797,28 @@ func dataForColumnsInTable(schema *model.DBInfo, tbl *model.TableInfo) [][]types
 		if colLen == types.UnspecifiedLength {
 			colLen = defaultFlen
 		}
+		if col.Tp == mysql.TypeSet {
+			// Example: In MySQL set('a','bc','def','ghij') has length 13, because
+			// len('a')+len('bc')+len('def')+len('ghij')+len(ThreeComma)=13
+			// Reference link: https://bugs.mysql.com/bug.php?id=22613
+			colLen = 0
+			for _, ele := range col.Elems {
+				colLen += len(ele)
+			}
+			if len(col.Elems) != 0 {
+				colLen += (len(col.Elems) - 1)
+			}
+		} else if col.Tp == mysql.TypeEnum {
+			// Example: In MySQL enum('a', 'ab', 'cdef') has length 4, because
+			// the longest string in the enum is 'cdef'
+			// Reference link: https://bugs.mysql.com/bug.php?id=22613
+			colLen = 0
+			for _, ele := range col.Elems {
+				if len(ele) > colLen {
+					colLen = len(ele)
+				}
+			}
+		}
 		if decimal == types.UnspecifiedLength {
 			decimal = defaultDecimal
 		}

infoschema/tables_test.go

@@ -77,6 +77,16 @@ func (s *testSuite) TestDataForTableRowsCountField(c *C) {
 	tk.MustExec("create user xxx")
 	tk.MustExec("flush privileges")
 
+	// Test for length of enum and set
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t ( s set('a','bc','def','ghij') default NULL, e1 enum('a', 'ab', 'cdef'), s2 SET('1','2','3','4','1585','ONE','TWO','Y','N','THREE'))")
+	tk.MustQuery("select column_name, character_maximum_length from information_schema.columns where table_schema=Database() and table_name = 't' and column_name = 's'").Check(
+		testkit.Rows("s 13"))
+	tk.MustQuery("select column_name, character_maximum_length from information_schema.columns where table_schema=Database() and table_name = 't' and column_name = 's2'").Check(
+		testkit.Rows("s2 30"))
+	tk.MustQuery("select column_name, character_maximum_length from information_schema.columns where table_schema=Database() and table_name = 't' and column_name = 'e1'").Check(
+		testkit.Rows("e1 4"))
+
 	tk1 := testkit.NewTestKit(c, store)
 	tk1.MustExec("use test")
 	c.Assert(tk1.Se.Auth(&auth.UserIdentity{