MWL#182: Explain running statements

- Make SHOW EXPLAIN command be KILLable with KILL QUERY.

3 files changed, 25 insertions, 8 deletions

diff --git a/sql/my_apc.cc b/sql/my_apc.cc
index 1cc13f41566..dd15daf48a2 100644
--- a/sql/my_apc.cc
+++ b/sql/my_apc.cc
@@ -145,8 +145,8 @@ void Apc_target::dequeue_request(Call_request *qe)
   to use thd->enter_cond() calls to be killable)
 */
 
-bool Apc_target::make_apc_call(Apc_call *call, int timeout_sec, 
-                               bool *timed_out)
+bool Apc_target::make_apc_call(THD *caller_thd, Apc_call *call, 
+                               int timeout_sec, bool *timed_out)
 {
   bool res= TRUE;
   *timed_out= FALSE;
@@ -166,6 +166,9 @@ bool Apc_target::make_apc_call(Apc_call *call, int timeout_sec,
     set_timespec(abstime, timeout);
 
     int wait_res= 0;
+    const char *old_msg;
+    old_msg= caller_thd->enter_cond(&apc_request.COND_request, 
+                                    LOCK_thd_data_ptr, "show_explain");
     /* todo: how about processing other errors here? */
     while (!apc_request.processed && (wait_res != ETIMEDOUT))
     {
@@ -173,13 +176,18 @@ bool Apc_target::make_apc_call(Apc_call *call, int timeout_sec,
       wait_res= mysql_cond_timedwait(&apc_request.COND_request,
                                      LOCK_thd_data_ptr, &abstime);
                                       // &apc_request.LOCK_request, &abstime);
+      if (caller_thd->killed)
+      {
+        break;
+      }
     }
 
     if (!apc_request.processed)
     {
       /* 
-        The wait has timed out. Remove the request from the queue (ok to do
-        because we own LOCK_thd_data_ptr.
+        The wait has timed out, or this thread was KILLed.
+        Remove the request from the queue (ok to do because we own
+        LOCK_thd_data_ptr)
       */
       apc_request.processed= TRUE;
       dequeue_request(&apc_request);
@@ -191,7 +199,10 @@ bool Apc_target::make_apc_call(Apc_call *call, int timeout_sec,
       /* Request was successfully executed and dequeued by the target thread */
       res= FALSE;
     }
-    mysql_mutex_unlock(LOCK_thd_data_ptr);
+    /* 
+      exit_cond() will call mysql_mutex_unlock(LOCK_thd_data_ptr) for us:
+    */
+    caller_thd->exit_cond(old_msg);
 
     /* Destroy all APC request data */
     mysql_cond_destroy(&apc_request.COND_request);
diff --git a/sql/my_apc.h b/sql/my_apc.h
index 93b934c9df1..84819b9beea 100644
--- a/sql/my_apc.h
+++ b/sql/my_apc.h
@@ -33,6 +33,8 @@
     requestor.
 */
 
+class THD;
+
 /*
   Target for asynchronous procedure calls (APCs). 
    - A target is running in some particular thread, 
@@ -62,7 +64,7 @@ public:
   };
   
   /* Make a call in the target thread (see function definition for details) */
-  bool make_apc_call(Apc_call *call, int timeout_sec, bool *timed_out);
+  bool make_apc_call(THD *caller_thd, Apc_call *call, int timeout_sec, bool *timed_out);
 
 #ifndef DBUG_OFF
   int n_calls_processed; /* Number of calls served by this target */
diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index d26c8f18340..6c407f0cec3 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -2084,11 +2084,15 @@ void mysqld_show_explain(THD *thd, const char *calling_user, ulong thread_id)
     explain_req.failed_to_produce= FALSE;
     
     /* Ok, we have a lock on target->LOCK_thd_data, can call: */
-    bres= tmp->apc_target.make_apc_call(&explain_req, timeout_sec, &timed_out);
+    bres= tmp->apc_target.make_apc_call(thd, &explain_req, timeout_sec, &timed_out);
 
     if (bres || explain_req.failed_to_produce)
     {
-      /* TODO not enabled or time out */
+      if (thd->killed)
+      {
+        thd->send_kill_message();
+      }
+      else 
       if (timed_out)
       {
         my_error(ER_ERROR_WHEN_EXECUTING_COMMAND, MYF(0),