Bug#40127 Multiple table DELETE IGNORE hangs on foreign key constraint violation

on 5.0            
The server crashes on an assert in net_end_statement indicating that the
Diagnostics area wasn't set properly during execution.
This happened on a multi table DELETE operation using the IGNORE keyword.
The keyword is suppose to allow for execution to continue on a best effort
despite some non-fatal errors. Instead execution stopped and no client
response was sent which would have led to a protocol error if it hadn't been
for the assert.
This patch corrects this issue by checking for the existence of an IGNORE
option before setting an error state during row-by-row delete iteration.

mysql-test/t/innodb_mysql.test

@@ -185,4 +185,151 @@ TRUNCATE TABLE t2;
 DROP TABLE t2;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#40127 Multiple table DELETE IGNORE hangs on foreign key constraint violation on 5.0
+--echo #
+CREATE TABLE t1 (
+        id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+        PRIMARY KEY (id)
+) ENGINE=InnoDB;
+
+CREATE TABLE t2 (
+        id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+        aid INT UNSIGNED NOT NULL,
+        PRIMARY KEY (id),
+        FOREIGN KEY (aid) REFERENCES t1 (id)
+) ENGINE=InnoDB;
+
+CREATE TABLE t3 (
+        bid INT UNSIGNED NOT NULL,
+        FOREIGN KEY (bid) REFERENCES t2 (id)
+) ENGINE=InnoDB;
+
+CREATE TABLE t4 (
+  a INT
+) ENGINE=InnoDB;
+
+CREATE TABLE t5 (
+  a INT
+) ENGINE=InnoDB;
+
+INSERT INTO t1 (id) VALUES (1);
+INSERT INTO t2 (id, aid) VALUES (1, 1),(2,1),(3,1),(4,1);
+INSERT INTO t3 (bid) VALUES (1);
+
+INSERT INTO t4 VALUES (1),(2),(3),(4),(5);
+INSERT INTO t5 VALUES (1);
+
+DELETE t5 FROM t4 LEFT JOIN t5 ON t4.a= t5.a;
+
+--error ER_ROW_IS_REFERENCED_2
+DELETE t2, t1 FROM t2 INNER JOIN t1 ON (t2.aid = t1.id) WHERE t2.id = 1;
+--error ER_ROW_IS_REFERENCED_2
+DELETE t2, t1 FROM t2 INNER JOIN t1 ON (t2.aid = t1.id) WHERE t2.id = 1;
+
+DELETE IGNORE t2, t1 FROM t2 INNER JOIN t1 ON (t2.aid = t1.id) WHERE t2.id = 1;
+
+DROP TABLE t3;
+DROP TABLE t2;
+DROP TABLE t1;
+DROP TABLES t4,t5;
+
+--echo # Bug#40127 Multiple table DELETE IGNORE hangs on foreign key constraint violation on 5.0
+--echo # Testing for any side effects of IGNORE on AFTER DELETE triggers used with
+--echo # transactional tables.
+--echo #
+CREATE TABLE t1 (i INT NOT NULL PRIMARY KEY) ENGINE=InnoDB;
+CREATE TABLE t2 (a VARCHAR(100)) ENGINE=InnoDB;
+CREATE TABLE t3 (i INT NOT NULL PRIMARY KEY) ENGINE=InnoDB;
+CREATE TABLE t4 (i INT NOT NULL PRIMARY KEY, t1i INT, 
+  FOREIGN KEY (t1i) REFERENCES t1(i))
+  ENGINE=InnoDB;
+delimiter ||;
+CREATE TRIGGER trg AFTER DELETE ON t1 FOR EACH ROW
+BEGIN
+  SET @b:='EXECUTED TRIGGER';
+  INSERT INTO t2 VALUES (@b);
+  SET @a:= error_happens_here;
+END||
+delimiter ;||
+
+SET @b:="";
+SET @a:="";
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+INSERT INTO t3 SELECT * FROM t1;
+--echo ** An error in a trigger causes rollback of the statement.
+--error ER_BAD_FIELD_ERROR
+DELETE t1 FROM t3 LEFT JOIN t1 ON t1.i=t3.i;
+SELECT @a,@b;
+SELECT * FROM t2;
+SELECT * FROM t1 LEFT JOIN t3 ON t1.i=t3.i;
+
+--echo ** Same happens with the IGNORE option
+--error ER_BAD_FIELD_ERROR
+DELETE IGNORE t1 FROM t3 LEFT JOIN t1 ON t1.i=t3.i;
+SELECT * FROM t2;
+SELECT * FROM t1 LEFT JOIN t3 ON t1.i=t3.i;
+
+--echo **
+--echo ** The following is an attempt to demonstrate
+--echo ** error handling inside a row iteration.
+--echo **
+DROP TRIGGER trg;
+TRUNCATE TABLE t1;
+TRUNCATE TABLE t2;
+TRUNCATE TABLE t3;
+
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+INSERT INTO t3 VALUES (1),(2),(3),(4);
+INSERT INTO t4 VALUES (3,3),(4,4);
+
+delimiter ||;
+CREATE TRIGGER trg AFTER DELETE ON t1 FOR EACH ROW
+BEGIN
+  SET @b:= CONCAT('EXECUTED TRIGGER FOR ROW ',CAST(OLD.i AS CHAR));
+  INSERT INTO t2 VALUES (@b);
+END||
+delimiter ;||
+
+--echo ** DELETE is prevented by foreign key constrains but errors are silenced.
+--echo ** The AFTER trigger isn't fired.
+DELETE IGNORE t1 FROM t3 LEFT JOIN t1 ON t1.i=t3.i;
+--echo ** Tables are modified by best effort:
+SELECT * FROM t1 LEFT JOIN t3 ON t1.i=t3.i;
+--echo ** The AFTER trigger was only executed on successful rows:
+SELECT * FROM t2;
+
+DROP TRIGGER trg;
+
+--echo **
+--echo ** Induce an error midway through an AFTER-trigger
+--echo **
+TRUNCATE TABLE t4;
+TRUNCATE TABLE t1;
+TRUNCATE TABLE t3;
+INSERT INTO t1 VALUES (1),(2),(3),(4);
+INSERT INTO t3 VALUES (1),(2),(3),(4);
+delimiter ||;
+CREATE TRIGGER trg AFTER DELETE ON t1 FOR EACH ROW
+BEGIN
+  SET @a:= @a+1;
+  IF @a > 2 THEN
+    INSERT INTO t4 VALUES (5,5);
+  END IF;
+END||
+delimiter ;||
+
+SET @a:=0;
+--echo ** Errors in the trigger causes the statement to abort.
+--error ER_NO_REFERENCED_ROW_2
+DELETE IGNORE t1 FROM t3 LEFT JOIN t1 ON t1.i=t3.i;
+SELECT * FROM t1 LEFT JOIN t3 ON t1.i=t3.i;
+SELECT * FROM t4;
+
+DROP TRIGGER trg;
+DROP TABLE t4;
+DROP TABLE t1;
+DROP TABLE t2;
+DROP TABLE t3;
+
 --echo End of 5.1 tests