Bug #16494: Updates that set a column to NULL fail sometimes

 When building the UPDATE query to send to the remote server, the
 federated storage engine built the query incorrectly if it was updating
 a field to be NULL.

 Thanks to Bjšrn Steinbrink for an initial patch for the problem.


mysql-test/r/federated.result:
  Add new results
mysql-test/t/federated.test:
  Add new regression test
sql/ha_federated.cc:
  Fix logic of how fields are added to SET and WHERE clauses of an
  UPDATE statement. Fields that were NULL were being handled incorrectly.
  Also reorganizes the code a little bit so the update of the two
  clauses is consistent.

1 files changed, 16 insertions, 0 deletions

diff --git a/mysql-test/r/federated.result b/mysql-test/r/federated.result
index f11da4ee62f..48f20625826 100644
--- a/mysql-test/r/federated.result
+++ b/mysql-test/r/federated.result
@@ -1601,6 +1601,22 @@ fld_cid	fld_name	fld_parentid	fld_delt
 5	Torkel	0	0
 DROP TABLE federated.t1;
 DROP TABLE federated.bug_17377_table;
+create table t1 (id int not null auto_increment primary key, val int);
+create table t1
+(id int not null auto_increment primary key, val int) engine=federated
+connection='mysql://root@127.0.0.1:9308/test/t1';
+insert into t1 values (1,0),(2,0);
+update t1 set val = NULL where id = 1;
+select * from t1;
+id	val
+1	NULL
+2	0
+select * from t1;
+id	val
+1	NULL
+2	0
+drop table t1;
+drop table t1;
 DROP TABLE IF EXISTS federated.t1;
 DROP DATABASE IF EXISTS federated;
 DROP TABLE IF EXISTS federated.t1;