Backport of a 5.0.74 fix into 5.0.72sp1:

BUG#38842 - Fix for 25951 seems incorrect

Original changeset:
> revision-id: svoj@mysql.com-20081111091051-54pr96nf1z2s30gx
> parent: vvaintroub@mysql.com-20081110201804-bi98gcs9avsf58ff
> committer: Sergey Vojtovich <svoj@mysql.com>
> branch nick: mysql-5.0-bugteam-bug38842
> timestamp: Tue 2008-11-11 13:10:51 +0400

mysql-test/r/fulltext.result

@@ -469,3 +469,31 @@ SELECT * FROM t1 WHERE MATCH(a) AGAINST ('"aaaa"' IN BOOLEAN MODE);
 a
  aaaaa aaaa
 DROP TABLE t1;
+CREATE TABLE t1 (a VARCHAR(255), b INT, FULLTEXT(a), KEY(b));
+INSERT INTO t1 VALUES('test', 1),('test', 1),('test', 1),('test', 1),
+('test', 1),('test', 2),('test', 3),('test', 4);
+EXPLAIN SELECT * FROM t1
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	fulltext	b,a	a	0		1	Using where
+EXPLAIN SELECT * FROM t1 USE INDEX(a)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	fulltext	a	a	0		1	Using where
+EXPLAIN SELECT * FROM t1 FORCE INDEX(a)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	fulltext	a	a	0		1	Using where
+EXPLAIN SELECT * FROM t1 IGNORE INDEX(a)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	b	b	5	const	4	Using where
+EXPLAIN SELECT * FROM t1 USE INDEX(b)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	b	b	5	const	4	Using where
+EXPLAIN SELECT * FROM t1 FORCE INDEX(b)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ref	b	b	5	const	4	Using where
+DROP TABLE t1;

mysql-test/t/fulltext.test

@@ -396,3 +396,30 @@ SELECT * FROM t1 WHERE MATCH(a) AGAINST ('"aaaa"' IN BOOLEAN MODE);
 DROP TABLE t1;
 
 # End of 4.1 tests
+
+#
+# BUG#38842 - Fix for 25951 seems incorrect
+#
+CREATE TABLE t1 (a VARCHAR(255), b INT, FULLTEXT(a), KEY(b));
+INSERT INTO t1 VALUES('test', 1),('test', 1),('test', 1),('test', 1),
+                     ('test', 1),('test', 2),('test', 3),('test', 4);
+
+EXPLAIN SELECT * FROM t1
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+
+EXPLAIN SELECT * FROM t1 USE INDEX(a)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+
+EXPLAIN SELECT * FROM t1 FORCE INDEX(a)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+
+EXPLAIN SELECT * FROM t1 IGNORE INDEX(a)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+
+EXPLAIN SELECT * FROM t1 USE INDEX(b)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+
+EXPLAIN SELECT * FROM t1 FORCE INDEX(b)
+WHERE MATCH(a) AGAINST('test' IN BOOLEAN MODE) AND b=1;
+
+DROP TABLE t1;

sql/item_func.cc

@@ -5022,7 +5022,9 @@ bool Item_func_match::fix_index()
   for (keynr=0 ; keynr < table->s->keys ; keynr++)
   {
     if ((table->key_info[keynr].flags & HA_FULLTEXT) &&
-        (table->s->keys_in_use.is_set(keynr)))
+        (flags & FT_BOOL ? table->keys_in_use_for_query.is_set(keynr) :
+                           table->s->keys_in_use.is_set(keynr)))
+
     {
       ft_to_key[fts]=keynr;
       ft_cnt[fts]=0;