*: Add support "show open tables" (#10166)

executor/show.go

@@ -130,6 +130,8 @@ func (e *ShowExec) fetchAll() error {
 		return e.fetchShowStatus()
 	case ast.ShowTables:
 		return e.fetchShowTables()
+	case ast.ShowOpenTables:
+		return e.fetchShowOpenTables()
 	case ast.ShowTableStatus:
 		return e.fetchShowTableStatus()
 	case ast.ShowTriggers:
@@ -223,6 +225,12 @@ func (e *ShowExec) fetchShowProcessList() error {
 	return nil
 }
 
+func (e *ShowExec) fetchShowOpenTables() error {
+	// TiDB has no concept like mysql's "table cache" and "open table"
+	// For simplicity, we just return an empty result with the same structure as MySQL's SHOW OPEN TABLES
+	return nil
+}
+
 func (e *ShowExec) fetchShowTables() error {
 	if !e.is.SchemaExists(e.DBName) {
 		return errors.Errorf("Can not find DB: %s", e.DBName)

executor/show_test.go

@@ -730,6 +730,12 @@ func (s *testSuite) TestShowSlow(c *C) {
 	tk.MustQuery(`admin show slow top all 3`)
 }
 
+func (s *testSuite) TestShowOpenTables(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustQuery("show open tables")
+	tk.MustQuery("show open tables in test")
+}
+
 func (s *testSuite) TestShowCreateTable(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")
@@ -742,7 +748,6 @@ func (s *testSuite) TestShowCreateTable(c *C) {
 			"  `ch2` varbinary(10) DEFAULT NULL\n"+
 			") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin",
 	))
-
 }
 
 func (s *testSuite) TestShowEscape(c *C) {

go.mod

@@ -78,3 +78,5 @@ require (
 	gopkg.in/natefinch/lumberjack.v2 v2.0.0
 	gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 // indirect
 )
+
+replace github.com/pingcap/parser => github.com/zimulala/parser v0.0.0-20190507040735-52f43e397b1e

go.sum

@@ -141,6 +141,8 @@ github.com/unrolled/render v0.0.0-20171102162132-65450fb6b2d3/go.mod h1:tu82oB5W
 github.com/xiang90/probing v0.0.0-20160813154853-07dd2e8dfe18 h1:MPPkRncZLN9Kh4MEFmbnK4h3BD7AUmskWv2+EeZJCCs=
 github.com/xiang90/probing v0.0.0-20160813154853-07dd2e8dfe18/go.mod h1:UETIi67q53MR2AWcXfiuqkDkRtnGDLqkBTpCHuJHxtU=
 github.com/yookoala/realpath v1.0.0/go.mod h1:gJJMA9wuX7AcqLy1+ffPatSCySA1FQ2S8Ya9AIoYBpE=
+github.com/zimulala/parser v0.0.0-20190507040735-52f43e397b1e h1:EfemAunuGpGitSTziAdQoQXJiSkGhoRxkgu/lFDXs8Y=
+github.com/zimulala/parser v0.0.0-20190507040735-52f43e397b1e/go.mod h1:G69sWhUqZ6QkeOjLFa/d9eJsBxH7Y/JhkqOyvz1gZ3M=
 go.uber.org/atomic v1.3.2 h1:2Oa65PReHzfn29GpvgsYwloV9AVFHPDk8tYxt2c2tr4=
 go.uber.org/atomic v1.3.2/go.mod h1:gD2HeocX3+yG+ygLZcrzQJaqmWj9AIm7n08wl/qW/PE=
 go.uber.org/multierr v1.1.0 h1:HoEmRHQPVSqub6w2z2d2EOVs2fjyFRGyofhKuyDq0QI=

planner/core/planbuilder.go

@@ -1623,6 +1623,9 @@ func buildShowSchema(s *ast.ShowStmt) (schema *expression.Schema) {
 		names = []string{"Engine", "Support", "Comment", "Transactions", "XA", "Savepoints"}
 	case ast.ShowDatabases:
 		names = []string{"Database"}
+	case ast.ShowOpenTables:
+		names = []string{"Database", "Table", "In_use", "Name_locked"}
+		ftypes = []byte{mysql.TypeVarchar, mysql.TypeVarchar, mysql.TypeLong, mysql.TypeLong}
 	case ast.ShowTables:
 		names = []string{fmt.Sprintf("Tables_in_%s", s.DBName)}
 		if s.Full {