max_session_mem_used server variable

mysql-test/r/mysqld--help.result

@@ -457,6 +457,10 @@ The following options may be given as the first argument:
  --max-seeks-for-key=# 
  Limit assumed max number of seeks when looking up rows
  based on a key
+ --max-session-mem-used=# 
+ Amount of memory a single user session is allowed to
+ allocate. This limits the value of the session variable
+ MEM_USED
  --max-sort-length=# The number of bytes to use when sorting BLOB or TEXT
  values (only the first max_sort_length bytes of each
  value are used; the rest are ignored)
@@ -1266,6 +1270,7 @@ max-long-data-size 4194304
 max-prepared-stmt-count 16382
 max-relay-log-size 1073741824
 max-seeks-for-key 18446744073709551615
+max-session-mem-used 9223372036854775807
 max-sort-length 1024
 max-sp-recursion-depth 0
 max-statement-time 0

mysql-test/suite/sys_vars/r/sysvars_server_embedded.result

@@ -1997,6 +1997,20 @@ NUMERIC_BLOCK_SIZE	1
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
+VARIABLE_NAME	MAX_SESSION_MEM_USED
+SESSION_VALUE	9223372036854775807
+GLOBAL_VALUE	9223372036854775807
+GLOBAL_VALUE_ORIGIN	COMPILE-TIME
+DEFAULT_VALUE	9223372036854775807
+VARIABLE_SCOPE	SESSION
+VARIABLE_TYPE	BIGINT UNSIGNED
+VARIABLE_COMMENT	Amount of memory a single user session is allowed to allocate. This limits the value of the session variable MEM_USED
+NUMERIC_MIN_VALUE	8192
+NUMERIC_MAX_VALUE	18446744073709551615
+NUMERIC_BLOCK_SIZE	1
+ENUM_VALUE_LIST	NULL
+READ_ONLY	NO
+COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	MAX_SORT_LENGTH
 SESSION_VALUE	1024
 GLOBAL_VALUE	1024

mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result

@@ -2193,6 +2193,20 @@ NUMERIC_BLOCK_SIZE	1
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
+VARIABLE_NAME	MAX_SESSION_MEM_USED
+SESSION_VALUE	9223372036854775807
+GLOBAL_VALUE	9223372036854775807
+GLOBAL_VALUE_ORIGIN	COMPILE-TIME
+DEFAULT_VALUE	9223372036854775807
+VARIABLE_SCOPE	SESSION
+VARIABLE_TYPE	BIGINT UNSIGNED
+VARIABLE_COMMENT	Amount of memory a single user session is allowed to allocate. This limits the value of the session variable MEM_USED
+NUMERIC_MIN_VALUE	8192
+NUMERIC_MAX_VALUE	18446744073709551615
+NUMERIC_BLOCK_SIZE	1
+ENUM_VALUE_LIST	NULL
+READ_ONLY	NO
+COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	MAX_SORT_LENGTH
 SESSION_VALUE	1024
 GLOBAL_VALUE	1024

sql/mysqld.cc

@@ -4001,6 +4001,15 @@ static void my_malloc_size_cb_func(long long size, my_bool is_thread_specific)
                         (longlong) thd->status_var.local_memory_used,
                         size));
     thd->status_var.local_memory_used+= size;
+    if (thd->status_var.local_memory_used > (int64)thd->variables.max_mem_used &&
+        !thd->killed)
+    {
+      char buf[1024];
+      thd->killed= KILL_QUERY;
+      my_snprintf(buf, sizeof(buf), "--max-thread-mem-used=%llu",
+                  thd->variables.max_mem_used);
+      my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), buf);
+    }
     DBUG_ASSERT((longlong) thd->status_var.local_memory_used >= 0);
   }
   else if (likely(thd))

sql/sql_class.cc

@@ -906,8 +906,8 @@ THD::THD(bool is_wsrep_applier)
 #endif
 {
   ulong tmp;
+  bzero(&variables, sizeof(variables));
 
-  mdl_context.init(this);
   /*
     We set THR_THD to temporally point to this THD to register all the
     variables that allocates memory for this THD
@@ -916,8 +916,11 @@ THD::THD(bool is_wsrep_applier)
   set_current_thd(this);
   status_var.local_memory_used= sizeof(THD);
   status_var.global_memory_used= 0;
+  variables.max_mem_used= global_system_variables.max_mem_used;
   main_da.init();
 
+  mdl_context.init(this);
+
   /*
     Pass nominal parameters to init_alloc_root only to ensure that
     the destructor works OK in case of an error. The main_mem_root
@@ -964,7 +967,6 @@ THD::THD(bool is_wsrep_applier)
   connection_name.str= 0;
   connection_name.length= 0;
 
-  bzero(&variables, sizeof(variables));
   file_id = 0;
   query_id= 0;
   query_name_consts= 0;

sql/sql_class.h

@@ -540,6 +540,7 @@ typedef struct system_variables
   ulonglong sortbuff_size;
   ulonglong group_concat_max_len;
   ulonglong default_regex_flags;
+  ulonglong max_mem_used;
 
   /**
      Place holders to store Multi-source variables in sys_var.cc during

sql/sys_vars.cc

@@ -5401,3 +5401,10 @@ static Sys_var_ulong Sys_log_tc_size(
        DEFAULT(my_getpagesize() * 6),
        BLOCK_SIZE(my_getpagesize()));
 #endif
+
+static Sys_var_ulonglong Sys_max_thread_mem(
+       "max_session_mem_used", "Amount of memory a single user session "
+       "is allowed to allocate. This limits the value of the "
+       "session variable MEM_USED", SESSION_VAR(max_mem_used),
+       CMD_LINE(REQUIRED_ARG), VALID_RANGE(8192,  ULONGLONG_MAX),
+       DEFAULT(LONGLONG_MAX), BLOCK_SIZE(1));