Bug #28476: force index on a disabled myisam index gives error 124

When processing the USE/FORCE index hints
the optimizer was not checking if the indexes 
specified are enabled (see ALTER TABLE).
Fixed by:
 Backporting the fix for bug 20604 to 5.0


mysql-test/r/key.result:
  Test for BUG 20604.
  The important part of the test is the explain output that 
  tests what indexes are used.
mysql-test/r/myisam.result:
  Bug #28476: test cases
mysql-test/t/key.test:
  Bug 20604: 
  The minimal test case that reveals the bug. The optimizer for 
  aggregates relies on keys disabled with ALTER TABLE ... DISABLE KEYS
  not being in the set TABLE::keys_in_use_for_query.
  When the execution engine tries to use a disabled index, MyISAM
  returns an error.
mysql-test/t/myisam.test:
  Bug #28476: test cases
sql/sql_base.cc:
  Bug #28476: 
   - Ignore disabled indexes in USE/FORCE index
sql/sql_select.cc:
  Bug 20604 : The intersection operation between table->s->keys_in_use 
  and table->keys_in_use_for_query is no longer necessary.
  We can trust that the latter is a subset of the former.
sql/table.h:
  Bug 20604:
  Added comments to TABLE_SHARE::keys_in_use and
  TABLE::keys_in_use_for_query.

4 files changed, 62 insertions, 0 deletions

diff --git a/mysql-test/r/key.result b/mysql-test/r/key.result
index ec15eaa97f5..3abc95ec3bf 100644
--- a/mysql-test/r/key.result
+++ b/mysql-test/r/key.result
@@ -455,3 +455,11 @@ ORDER BY c.b, c.d
 a	b	c	d	e	f	g	h	i	j	a	b	c	d
 2	2	1	2004-11-30 12:00:00	1	0	0	0	0	0	2	3388000	-553000	NULL
 DROP TABLE t1, t2;
+CREATE TABLE t1( a TINYINT, KEY(a) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES( 1 );
+ALTER TABLE t1 DISABLE KEYS;
+EXPLAIN SELECT MAX(a) FROM t1 FORCE INDEX(a);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
+DROP TABLE t1;
+End of 5.0 tests.
diff --git a/mysql-test/r/myisam.result b/mysql-test/r/myisam.result
index 94f2f1f72b3..7fc29cd13ca 100644
--- a/mysql-test/r/myisam.result
+++ b/mysql-test/r/myisam.result
@@ -1780,4 +1780,30 @@ create table t3 (c1 int) engine=myisam pack_keys=default;
 create table t4 (c1 int) engine=myisam pack_keys=2;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '2' at line 1
 drop table t1, t2, t3;
+CREATE TABLE t1(a INT, b INT, KEY inx (a), UNIQUE KEY uinx (b)) ENGINE=MyISAM;
+INSERT INTO t1(a,b) VALUES (1,1),(2,2),(3,3),(4,4),(5,5);
+SELECT a FROM t1 FORCE INDEX (inx) WHERE a=1;
+a
+1
+ALTER TABLE t1 DISABLE KEYS;
+SELECT a FROM t1 FORCE INDEX (inx) WHERE a=1;
+a
+1
+SELECT a FROM t1 USE INDEX (inx) WHERE a=1;
+a
+1
+SELECT b FROM t1 FORCE INDEX (uinx) WHERE b=1;
+b
+1
+SELECT b FROM t1 USE INDEX (uinx) WHERE b=1;
+b
+1
+SELECT a FROM t1 FORCE INDEX (inx,uinx) WHERE a=1;
+a
+1
+ALTER TABLE t1 ENABLE KEYS;
+SELECT a FROM t1 FORCE INDEX (inx) WHERE a=1;
+a
+1
+DROP TABLE t1;
 End of 5.0 tests
diff --git a/mysql-test/t/key.test b/mysql-test/t/key.test
index e84b2071ab1..3d0e68dc0f3 100644
--- a/mysql-test/t/key.test
+++ b/mysql-test/t/key.test
@@ -432,3 +432,15 @@ ORDER BY c.b, c.d
 ;
 
 DROP TABLE t1, t2;
+
+
+#
+# Bug #20604: Test for disabled keys with aggregate functions and FORCE INDEX.
+#
+CREATE TABLE t1( a TINYINT, KEY(a) ) ENGINE=MyISAM;
+INSERT INTO t1 VALUES( 1 );
+ALTER TABLE t1 DISABLE KEYS;
+EXPLAIN SELECT MAX(a) FROM t1 FORCE INDEX(a);
+DROP TABLE t1;
+
+--echo End of 5.0 tests.
diff --git a/mysql-test/t/myisam.test b/mysql-test/t/myisam.test
index 82d10059c65..12b9423be21 100644
--- a/mysql-test/t/myisam.test
+++ b/mysql-test/t/myisam.test
@@ -1145,4 +1145,20 @@ create table t3 (c1 int) engine=myisam pack_keys=default;
 create table t4 (c1 int) engine=myisam pack_keys=2;
 drop table t1, t2, t3;
 
+#
+# Bug#28476: force index on a disabled myisam index gives error 124
+#
+CREATE TABLE t1(a INT, b INT, KEY inx (a), UNIQUE KEY uinx (b)) ENGINE=MyISAM;
+INSERT INTO t1(a,b) VALUES (1,1),(2,2),(3,3),(4,4),(5,5);
+SELECT a FROM t1 FORCE INDEX (inx) WHERE a=1;
+ALTER TABLE t1 DISABLE KEYS;
+SELECT a FROM t1 FORCE INDEX (inx) WHERE a=1;
+SELECT a FROM t1 USE INDEX (inx) WHERE a=1;
+SELECT b FROM t1 FORCE INDEX (uinx) WHERE b=1;
+SELECT b FROM t1 USE INDEX (uinx) WHERE b=1;
+SELECT a FROM t1 FORCE INDEX (inx,uinx) WHERE a=1;
+ALTER TABLE t1 ENABLE KEYS;
+SELECT a FROM t1 FORCE INDEX (inx) WHERE a=1;
+DROP TABLE t1;
+
 --echo End of 5.0 tests