MDEV-6394: ANALYZE DELETE .. RETURNING fails with ERROR 2027 Malformed packet (now, the code)

Forgot the code

sql/sql_delete.cc

@@ -259,6 +259,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
                                             select_lex->item_list, &conds))
     DBUG_RETURN(TRUE);
   
+  if (with_select)
     (void) result->prepare(select_lex->item_list, NULL);
 
   if (thd->lex->current_select->first_cond_optimization)
@@ -672,17 +673,21 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   }
   DBUG_ASSERT(transactional_table || !deleted || thd->transaction.stmt.modified_non_trans_table);
   
-  if (thd->lex->analyze_stmt)
-    goto emit_explain_and_leave;
 
   free_underlaid_joins(thd, select_lex);
   if (error < 0 || 
       (thd->lex->ignore && !thd->is_error() && !thd->is_fatal_error))
   {
-    if (!with_select)
-      my_ok(thd, deleted);
-    else
+    if (thd->lex->analyze_stmt)
+    {
+      error= 0;
+      goto send_nothing_and_leave;
+    }
+
+    if (with_select)
       result->send_eof();
+    else
+      my_ok(thd, deleted);
     DBUG_PRINT("info",("%ld records deleted",(long) deleted));
   }
   DBUG_RETURN(error >= 0 || thd->is_error());
@@ -695,13 +700,17 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   */
   query_plan.save_explain_data(thd->lex->explain);
 
-emit_explain_and_leave:
-  int err2= thd->lex->explain->send_explain(thd);
+send_nothing_and_leave:
+  /* 
+    ANALYZE DELETE jumps here. We can't send explain right here, because
+    we might be using ANALYZE DELETE ...RETURNING, in which case we have 
+    Protocol_discard active.
+  */
 
   delete select;
   free_underlaid_joins(thd, select_lex);
   //table->set_keyread(false);
-  DBUG_RETURN((err2 || thd->is_error() || thd->killed) ? 1 : 0);
+  DBUG_RETURN((thd->is_error() || thd->killed) ? 1 : 0);
 }
 
 

sql/sql_parse.cc

@@ -3567,12 +3567,47 @@ case SQLCOM_PREPARE:
     unit->set_limit(select_lex);
 
     MYSQL_DELETE_START(thd->query());
+    Protocol *save_protocol;
+    bool replaced_protocol= false;
+
+    if (!select_lex->item_list.is_empty())
+    {
+      /* This is DELETE ... RETURNING.  It will return output to the client */
+      if (thd->lex->analyze_stmt)
+      {
+        /* 
+          Actually, it is ANALYZE .. DELETE .. RETURNING. We need to produce
+          output and then discard it.
+        */
+        sel_result= new select_send_analyze();
+        replaced_protocol= true;
+        save_protocol= thd->protocol;
+        thd->protocol= new Protocol_discard(thd);
+      }
+      else
+      {
         if (!(sel_result= lex->result) && !(sel_result= new select_send()))
           return 1;
+      }
+    }
+
     res = mysql_delete(thd, all_tables, 
                        select_lex->where, &select_lex->order_list,
                        unit->select_limit_cnt, select_lex->options,
                        sel_result);
+
+    if (replaced_protocol)
+    {
+      delete thd->protocol;
+      thd->protocol= save_protocol;
+    }
+
+    if (thd->lex->analyze_stmt || thd->lex->describe)
+    {
+      if (!res)
+        res= thd->lex->explain->send_explain(thd);
+    }
+
     delete sel_result;
     MYSQL_DELETE_DONE(res, (ulong) thd->get_row_count_func());
     break;