From ec8351ca9a6cbc04e84ae8d01ab3770802b45cd5 Mon Sep 17 00:00:00 2001
From: Chengpeng Yan <41809508+Reminiscent@users.noreply.github.com>
Date: Tue, 3 Aug 2021 16:47:07 +0800
Subject: [PATCH] bindinfo: add status vars for 'last_plan_binding_update_time'
 (#26340)

---
 bindinfo/bind_test.go | 28 ++++++++++++++++++++++++++++
 bindinfo/handle.go    |  1 +
 bindinfo/stat.go      | 39 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 68 insertions(+)
 create mode 100644 bindinfo/stat.go

diff --git a/bindinfo/bind_test.go b/bindinfo/bind_test.go
index 256c1be1ec036..e168122354e3b 100644
--- a/bindinfo/bind_test.go
+++ b/bindinfo/bind_test.go
@@ -2132,3 +2132,31 @@ func (s *testSuite) TestTemporaryTable(c *C) {
 	tk.MustGetErrCode("create binding for update t set a = 1 where b = 1 and c > 1 using update /*+ use_index(t, c) */ t set a = 1 where b = 1 and c > 1", errno.ErrOptOnTemporaryTable)
 	tk.MustGetErrCode("create binding for delete from t where b = 1 and c > 1 using delete /*+ use_index(t, c) */ from t where b = 1 and c > 1", errno.ErrOptOnTemporaryTable)
 }
+
+func (s *testSuite) TestBindingLastUpdateTime(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	s.cleanBindingEnv(tk)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t0;")
+	tk.MustExec("create table t0(a int, key(a));")
+	tk.MustExec("create global binding for select * from t0 using select * from t0 use index(a);")
+	tk.MustExec("admin reload bindings;")
+
+	bindHandle := bindinfo.NewBindHandle(tk.Se)
+	err := bindHandle.Update(true)
+	c.Check(err, IsNil)
+	sql, hash := parser.NormalizeDigest("select * from test . t0")
+	bindData := bindHandle.GetBindRecord(hash.String(), sql, "test")
+	c.Assert(len(bindData.Bindings), Equals, 1)
+	bind := bindData.Bindings[0]
+	updateTime := bind.UpdateTime.String()
+
+	rows1 := tk.MustQuery("show status like 'last_plan_binding_update_time';").Rows()
+	updateTime1 := rows1[0][1]
+	c.Assert(updateTime1, Equals, updateTime)
+
+	rows2 := tk.MustQuery("show session status like 'last_plan_binding_update_time';").Rows()
+	updateTime2 := rows2[0][1]
+	c.Assert(updateTime2, Equals, updateTime)
+	tk.MustQuery(`show global status like 'last_plan_binding_update_time';`).Check(testkit.Rows())
+}
diff --git a/bindinfo/handle.go b/bindinfo/handle.go
index 2281af3c88bd3..a69c0638d2dc3 100644
--- a/bindinfo/handle.go
+++ b/bindinfo/handle.go
@@ -114,6 +114,7 @@ func NewBindHandle(ctx sessionctx.Context) *BindHandle {
 		// BindSQL has already been validated when coming here, so we use nil sctx parameter.
 		return handle.AddBindRecord(nil, record)
 	}
+	variable.RegisterStatistics(handle)
 	return handle
 }
 
diff --git a/bindinfo/stat.go b/bindinfo/stat.go
new file mode 100644
index 0000000000000..aea98669002d1
--- /dev/null
+++ b/bindinfo/stat.go
@@ -0,0 +1,39 @@
+// Copyright 2021 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package bindinfo
+
+import (
+	"github.com/pingcap/tidb/sessionctx/variable"
+)
+
+var (
+	lastPlanBindingUpdateTime = "last_plan_binding_update_time"
+)
+
+// GetScope gets the status variables scope.
+func (h *BindHandle) GetScope(status string) variable.ScopeFlag {
+	return variable.ScopeSession
+}
+
+// Stats returns the server statistics.
+func (h *BindHandle) Stats(vars *variable.SessionVars) (map[string]interface{}, error) {
+	h.bindInfo.Lock()
+	defer func() {
+		h.bindInfo.Unlock()
+	}()
+	m := make(map[string]interface{})
+	m[lastPlanBindingUpdateTime] = h.bindInfo.lastUpdateTime.String()
+
+	return m, nil
+}