BUG#20821 (INSERT DELAYED failes to write some rows to binlog):

Fixing typo and potential memory problem.
Reducing number of concurrent mysqlslap threads since tests fail
in pushbuild due to too many threads.

mysql-test/r/rpl_insert.result

@@ -9,8 +9,8 @@ USE mysqlslap;
 CREATE TABLE t1 (id INT, name VARCHAR(64));
 SELECT COUNT(*) FROM mysqlslap.t1;
 COUNT(*)
-20000
+5000
 SELECT COUNT(*) FROM mysqlslap.t1;
 COUNT(*)
-20000
+5000
 DROP SCHEMA IF EXISTS mysqlslap;

mysql-test/t/rpl_insert.test

@@ -15,7 +15,7 @@ USE mysqlslap;
 CREATE TABLE t1 (id INT, name VARCHAR(64));
 
 let $query = "INSERT DELAYED INTO t1 VALUES (1, 'Dr. No'), (2, 'From Russia With Love'), (3, 'Goldfinger'), (4, 'Thunderball'), (5, 'You Only Live Twice')";
---exec $MYSQL_SLAP --silent --concurrency=20 --iterations=200 --query=$query --delimiter=";"
+--exec $MYSQL_SLAP --silent --concurrency=5 --iterations=200 --query=$query --delimiter=";"
 
 --sleep 10
 

sql/sql_insert.cc

@@ -1638,8 +1638,12 @@ write_delayed(THD *thd,TABLE *table, enum_duplicates duplic,
    */
 
   if (query.str)
-    if (!(query.str= my_strndup(query.str, MYF(MY_WME), query.length)))
+  {
+    char *str;
+    if (!(str= my_strndup(query.str, query.length, MYF(MY_WME))))
       goto err;
+    query.str= str;
+  }
   row= new delayed_row(query, duplic, ignore, log_on);
   if (row == NULL)
   {