planner: remove duplicated pseudo bindings after loading data with BR

pkg/bindinfo/handle.go

@@ -99,6 +99,14 @@ const (
 	Prompt = "bindinfo"
 	// BuiltinPseudoSQL4BindLock is used to simulate LOCK TABLE for mysql.bind_info.
 	BuiltinPseudoSQL4BindLock = "builtin_pseudo_sql_for_bind_lock"
+
+	// StmtRemoveDuplicatedPseudoBinding is used to remove duplicated pseudo binding.
+	// After using BR to sync bind_info between two clusters, the pseudo binding may be duplicated, and
+	// BR use this statement to remove duplicated rows, and this SQL should only be executed by BR.
+	StmtRemoveDuplicatedPseudoBinding = `DELETE FROM mysql.bind_info
+       WHERE original_sql='builtin_pseudo_sql_for_bind_lock' AND
+       _tidb_rowid NOT IN ( -- keep one arbitrary pseudo binding
+         SELECT _tidb_rowid FROM mysql.bind_info WHERE original_sql='builtin_pseudo_sql_for_bind_lock' limit 1)`
 )
 
 type bindRecordUpdate struct {

pkg/bindinfo/handle_test.go

@@ -607,3 +607,37 @@ func TestReloadBindings(t *testing.T) {
 	rows = tk.MustQuery("show global bindings").Rows()
 	require.Equal(t, 0, len(rows))
 }
+
+func TestRemoveDuplicatedPseudoBinding(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+
+	checkPseudoBinding := func(num int) {
+		tk.MustQuery(fmt.Sprintf("select count(1) from mysql.bind_info where original_sql='%s'",
+			bindinfo.BuiltinPseudoSQL4BindLock)).Check(testkit.Rows(fmt.Sprintf("%d", num)))
+	}
+	insertPseudoBinding := func() {
+		tk.MustExec(fmt.Sprintf(`INSERT INTO mysql.bind_info(original_sql, bind_sql, default_db, status, create_time, update_time, charset, collation, source)
+            VALUES ('%v', '%v', "mysql", '%v', "2000-01-01 00:00:00", "2000-01-01 00:00:00", "", "", '%v')`,
+			bindinfo.BuiltinPseudoSQL4BindLock, bindinfo.BuiltinPseudoSQL4BindLock, bindinfo.Builtin, bindinfo.Builtin))
+	}
+	removeDuplicated := func() {
+		tk.MustExec(bindinfo.StmtRemoveDuplicatedPseudoBinding)
+	}
+
+	checkPseudoBinding(1)
+	insertPseudoBinding()
+	checkPseudoBinding(2)
+	removeDuplicated()
+	checkPseudoBinding(1)
+
+	insertPseudoBinding()
+	insertPseudoBinding()
+	insertPseudoBinding()
+	checkPseudoBinding(4)
+	removeDuplicated()
+	checkPseudoBinding(1)
+	removeDuplicated()
+	checkPseudoBinding(1)
+}