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:
  Add result for bug#16461.
mysql-test/t/trigger.test:
  Add test case for bug#16461.
sql/item.cc:
  Remove now unused class Item_static_int_func.
sql/item.h:
  Remove now unused class Item_static_int_func.
sql/item_create.cc:
  Use new implementation of CONNECTION_ID().
sql/item_func.cc:
  Re-implement CONNECTION_ID() as Item_func_connection_id
  (was Item_static_int_func).  Set max_length to 10, as it was before.
  Compute connection_id dynamically on every call to fix_fields().
sql/item_func.h:
  Re-implement CONNECTION_ID() as Item_func_connection_id
  (was Item_static_int_func).

1 files changed, 28 insertions, 0 deletions

diff --git a/mysql-test/t/trigger.test b/mysql-test/t/trigger.test
index c5925bbd9d5..a0b67b2204d 100644
--- a/mysql-test/t/trigger.test
+++ b/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