BUG#25951 - ignore/use index does not work with fulltext

IGNORE/USE/FORCE INDEX hints were honored when choosing FULLTEXT
index.

With this fix these hints are ignored. For regular indexes we may
perform table scan instead of index lookup when IGNORE INDEX was
specified. We cannot do this for FULLTEXT in NLQ mode.

mysql-test/r/fulltext.result

@@ -447,3 +447,10 @@ a	MATCH(a) AGAINST('test1 test')
 test1	0.68526661396027
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
+CREATE TABLE t1 (a VARCHAR(255), FULLTEXT(a));
+SELECT * FROM t1 IGNORE INDEX(a) WHERE MATCH(a) AGAINST('test');
+a
+ALTER TABLE t1 DISABLE KEYS;
+SELECT * FROM t1 WHERE MATCH(a) AGAINST('test');
+ERROR HY000: Can't find FULLTEXT index matching the column list
+DROP TABLE t1;

mysql-test/t/fulltext.test

@@ -369,4 +369,14 @@ EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
 
+#
+# BUG#25951 - ignore/use index does not work with fulltext
+#
+CREATE TABLE t1 (a VARCHAR(255), FULLTEXT(a));
+SELECT * FROM t1 IGNORE INDEX(a) WHERE MATCH(a) AGAINST('test');
+ALTER TABLE t1 DISABLE KEYS;
+--error 1191
+SELECT * FROM t1 WHERE MATCH(a) AGAINST('test');
+DROP TABLE t1;
+
 # End of 4.1 tests

sql/item_func.cc

@@ -3158,7 +3158,7 @@ bool Item_func_match::fix_index()
   for (keynr=0 ; keynr < table->keys ; keynr++)
   {
     if ((table->key_info[keynr].flags & HA_FULLTEXT) &&
-        (table->keys_in_use_for_query.is_set(keynr)))
+        (table->keys_in_use.is_set(keynr)))
     {
       ft_to_key[fts]=keynr;
       ft_cnt[fts]=0;