Enable PERFORMANCE_SCHEMA tracking for SHOW EXPLAIN's conditions.

mysql-test/r/show_explain_ps.result

+drop table if exists t0, t1;
+select * from performance_schema.setup_instruments where name like '%show_explain%';
+NAME	ENABLED	TIMED
+wait/synch/cond/sql/show_explain	YES	YES
+# We've got no instances
+select * from performance_schema.cond_instances where name like '%show_explain%';
+NAME	OBJECT_INSTANCE_BEGIN
+# Check out if our cond is hit.
+create table t0 (a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+set @show_explain_probe_select_id=1;
+set debug_dbug='d,show_explain_probe_join_exec_start';
+select count(*) from t0 where a < 100000;
+show explain for $thr2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
+Warnings:
+Note	1003	select count(*) from t0 where a < 100000
+count(*)
+10
+set debug_dbug='';
+select event_name
+from performance_schema.events_waits_history_long 
+where event_name='wait/synch/cond/sql/show_explain';
+event_name
+wait/synch/cond/sql/show_explain
+drop table t0;

mysql-test/t/show_explain_ps.test

+#
+# Test how SHOW EXPLAIN is represented in performance schema
+#
+--source include/have_perfschema.inc
+
+--disable_warnings
+drop table if exists t0, t1;
+--enable_warnings
+
+select * from performance_schema.setup_instruments where name like '%show_explain%';
+
+--echo # We've got no instances
+select * from performance_schema.cond_instances where name like '%show_explain%';
+
+--echo # Check out if our cond is hit.
+
+create table t0 (a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+
+let $thr1=`select connection_id()`;
+connect (con1, localhost, root,,);
+connection con1;
+let $thr2=`select connection_id()`;
+connection default;
+
+let $wait_condition= select State='show_explain_trap' from information_schema.processlist where id=$thr2;
+
+#
+# Test SHOW EXPLAIN for simple queries
+#
+connection con1;
+set @show_explain_probe_select_id=1;
+set debug_dbug='d,show_explain_probe_join_exec_start';
+send select count(*) from t0 where a < 100000;
+
+connection default;
+--source include/wait_condition.inc
+evalp show explain for $thr2;
+connection con1;
+reap;
+
+set debug_dbug='';
+
+select event_name
+from performance_schema.events_waits_history_long 
+where event_name='wait/synch/cond/sql/show_explain';
+
+drop table t0;

sql/my_apc.cc

@@ -124,6 +124,26 @@ void Apc_target::dequeue_request(Call_request *qe)
   qe->next->prev= qe->prev;
 }
 
+#ifdef HAVE_PSI_INTERFACE
+
+/* One key for all conds */
+PSI_cond_key key_show_explain_request_COND;
+
+static PSI_cond_info show_explain_psi_conds[]=
+{
+  { &key_show_explain_request_COND, "show_explain", 0 /* not using PSI_FLAG_GLOBAL*/ }
+};
+
+void init_show_explain_psi_keys(void)
+{
+  if (PSI_server == NULL)
+    return;
+
+  PSI_server->register_cond("sql", show_explain_psi_conds, 
+                            array_elements(show_explain_psi_conds));
+}
+#endif
+
 
 /*
   Make an APC (Async Procedure Call) to another thread. 
@@ -154,7 +174,8 @@ bool Apc_target::make_apc_call(THD *caller_thd, Apc_call *call,
     Call_request apc_request;
     apc_request.call= call;
     apc_request.processed= FALSE;
-    mysql_cond_init(0 /* do not track in PS */, &apc_request.COND_request, NULL);
+    mysql_cond_init(key_show_explain_request_COND, &apc_request.COND_request,
+                    NULL);
     enqueue_request(&apc_request);
     apc_request.what="enqueued by make_apc_call";
  
@@ -174,9 +195,7 @@ bool Apc_target::make_apc_call(THD *caller_thd, Apc_call *call,
                                      LOCK_thd_data_ptr, &abstime);
                                       // &apc_request.LOCK_request, &abstime);
       if (caller_thd->killed)
-      {
         break;
-      }
     }
 
     if (!apc_request.processed)

sql/my_apc.h

@@ -119,3 +119,7 @@ class Apc_target
   }
 };
 
+#ifdef HAVE_PSI_INTERFACE
+void init_show_explain_psi_keys(void);
+#endif
+

sql/mysqld.cc

@@ -3909,6 +3909,7 @@ static int init_thread_environment()
   sp_cache_init();
 #ifdef HAVE_EVENT_SCHEDULER
   Events::init_mutexes();
+  init_show_explain_psi_keys();
 #endif
   /* Parameter for threads created for connections */
   (void) pthread_attr_init(&connection_attrib);