Bug#16461: connection_id() does not work properly inside trigger

CONNECTION_ID() was implemented as a constant Item, i.e. an instance of
Item_static_int_func class holding value computed at creation time.
Since Items are created on parsing, and trigger statements are parsed
on table open, the first connection to open a particular table would
effectively set its own CONNECTION_ID() inside trigger statements for
that table.

Re-implement CONNECTION_ID() as a class derived from Item_int_func, and
compute connection_id on every call to fix_fields().

mysql-test/r/trigger.result

@@ -952,3 +952,16 @@ load data infile '../std_data_ln/words.dat' into table t1 (a) set b:= f1();
 drop table t1;
 drop function f1;
 drop function f2;
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1 (
+conn_id INT,
+trigger_conn_id INT
+);
+CREATE TRIGGER t1_bi BEFORE INSERT ON t1 FOR EACH ROW
+SET NEW.trigger_conn_id = CONNECTION_ID();
+INSERT INTO t1 (conn_id, trigger_conn_id) VALUES (CONNECTION_ID(), -1);
+INSERT INTO t1 (conn_id, trigger_conn_id) VALUES (CONNECTION_ID(), -1);
+SELECT * FROM t1 WHERE conn_id != trigger_conn_id;
+conn_id	trigger_conn_id
+DROP TRIGGER t1_bi;
+DROP TABLE t1;

mysql-test/t/trigger.test

@@ -1114,3 +1114,31 @@ load data infile '../std_data_ln/words.dat' into table t1 (a) set b:= f1();
 drop table t1;
 drop function f1;
 drop function f2;
+
+#
+# Test for Bug #16461 connection_id() does not work properly inside trigger
+#
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+
+CREATE TABLE t1 (
+    conn_id INT,
+    trigger_conn_id INT
+);
+CREATE TRIGGER t1_bi BEFORE INSERT ON t1 FOR EACH ROW
+  SET NEW.trigger_conn_id = CONNECTION_ID();
+
+INSERT INTO t1 (conn_id, trigger_conn_id) VALUES (CONNECTION_ID(), -1);
+
+connect (con1,localhost,root,,);
+INSERT INTO t1 (conn_id, trigger_conn_id) VALUES (CONNECTION_ID(), -1);
+connection default;
+disconnect con1;
+
+SELECT * FROM t1 WHERE conn_id != trigger_conn_id;
+
+DROP TRIGGER t1_bi;
+DROP TABLE t1;
+
+# End of 5.0 tests

sql/item.cc

@@ -644,22 +644,6 @@ Item *Item_num::safe_charset_converter(CHARSET_INFO *tocs)
 }
 
 
-Item *Item_static_int_func::safe_charset_converter(CHARSET_INFO *tocs)
-{
-  Item_string *conv;
-  char buf[64];
-  String *s, tmp(buf, sizeof(buf), &my_charset_bin);
-  s= val_str(&tmp);
-  if ((conv= new Item_static_string_func(func_name, s->ptr(), s->length(),
-                                         s->charset())))
-  {
-    conv->str_value.copy();
-    conv->str_value.mark_as_const();
-  }
-  return conv;
-}
-
-
 Item *Item_static_float_func::safe_charset_converter(CHARSET_INFO *tocs)
 {
   Item_string *conv;

sql/item.h

@@ -1387,18 +1387,6 @@ public:
 };
 
 
-class Item_static_int_func :public Item_int
-{
-  const char *func_name;
-public:
-  Item_static_int_func(const char *str_arg, longlong i, uint length)
-    :Item_int(NullS, i, length), func_name(str_arg)
-  {}
-  Item *safe_charset_converter(CHARSET_INFO *tocs);
-  void print(String *str) { str->append(func_name); }
-};
-
-
 class Item_uint :public Item_int
 {
 public:

sql/item_create.cc

@@ -71,14 +71,8 @@ Item *create_func_ceiling(Item* a)
 
 Item *create_func_connection_id(void)
 {
-  THD *thd=current_thd;
-  thd->lex->safe_to_cache_query= 0;
-  return new Item_static_int_func("connection_id()",
-                                  (longlong)
-                                  ((thd->slave_thread) ?
-                                   thd->variables.pseudo_thread_id :
-                                   thd->thread_id),
-                                  10);
+  current_thd->lex->safe_to_cache_query= 0;
+  return new Item_func_connection_id();
 }
 
 Item *create_func_conv(Item* a, Item *b, Item *c)

sql/item_func.cc

@@ -559,6 +559,31 @@ String *Item_int_func::val_str(String *str)
 }
 
 
+void Item_func_connection_id::fix_length_and_dec()
+{
+  Item_int_func::fix_length_and_dec();
+  max_length= 10;
+}
+
+
+bool Item_func_connection_id::fix_fields(THD *thd, Item **ref)
+{
+  if (Item_int_func::fix_fields(thd, ref))
+    return TRUE;
+
+  /*
+    To replicate CONNECTION_ID() properly we should use
+    pseudo_thread_id on slave, which contains the value of thread_id
+    on master.
+  */
+  value= ((thd->slave_thread) ?
+          thd->variables.pseudo_thread_id :
+          thd->thread_id);
+
+  return FALSE;
+}
+
+
 /*
   Check arguments here to determine result's type for a numeric
   function of two arguments.

sql/item_func.h

@@ -279,6 +279,18 @@ public:
 };
 
 
+class Item_func_connection_id :public Item_int_func
+{
+  longlong value;
+
+public:
+  const char *func_name() const { return "connection_id"; }
+  void fix_length_and_dec();
+  bool fix_fields(THD *thd, Item **ref);
+  longlong val_int() { DBUG_ASSERT(fixed == 1); return value; }
+};
+
+
 class Item_func_signed :public Item_int_func
 {
 public: