InnoDB's estimate for the index cardinality depends on a pseudo random
number generator (it picks up random pages to sample). After an
optimization that was made in r2625 the following EXPLAINs started
returning a different number of rows (3 instead of 4).

This patch replaces whatever is returned for number of rows with 4 so
that the test does not fail.

This patch cannot be proposed to MySQL because the failures occur only
in this tree and do not occur in the standard InnoDB 5.1. Furthermore,
the file index_merge2.inc is used by other engines too.

--- mysql-test/include/index_merge2.inc.orig	2008-09-26 13:41:50.000000000 +0300
+++ mysql-test/include/index_merge2.inc	2008-09-26 14:32:58.000000000 +0300
@@ -122,12 +122,14 @@
 analyze table t1;
 select count(*) from t1;
 
+-- replace_column 9 4
 explain select count(*) from t1 where
   key1a = 2 and key1b is null and  key2a = 2 and key2b is null;
 
 select count(*) from t1 where
   key1a = 2 and key1b is null and key2a = 2 and key2b is null;
 
+-- replace_column 9 4
 explain select count(*) from t1 where
   key1a = 2 and key1b is null and key3a = 2 and key3b is null;