Failing test case.

t/lib/NibbleIterator.t

@@ -831,6 +831,26 @@ is_deeply(
    "Bug 995274: nibble iter works"
 );
 
+
+# #############################################################################
+# pt-table-checksum doesn't use non-unique index with highest cardinality
+# https://bugs.launchpad.net/percona-toolkit/+bug/1199591
+# #############################################################################
+
+diag(`/tmp/12345/use < $trunk/t/lib/samples/cardinality.sql >/dev/null`);
+
+$ni = make_nibble_iter(
+   db   => 'cardb',
+   tbl  => 't',
+   argv => [qw(--databases cardb --chunk-size 2)],
+);
+
+is(
+   $ni->{index},
+   'b',
+   "Use non-unique index with highest cardinality (bug 1199591)"
+);
+
 # #############################################################################
 # Done.
 # #############################################################################

t/lib/samples/cardinality.sql

@@ -0,0 +1,49 @@
+DROP DATABASE IF EXISTS cardb;
+CREATE DATABASE cardb;
+USE cardb;
+CREATE TABLE t (
+  high  INT UNSIGNED NOT NULL,
+  low   INT UNSIGNED NOT NULL,
+  INDEX a (low),
+  INDEX b (high),
+  INDEX c (low)
+) ENGINE=InnoDB;
+INSERT INTO t VALUES
+  (1,   1),
+  (2,   1),
+  (3,   1),
+  (4,   1),
+  (5,   1),
+  (6,   1),
+  (7,   1),
+  (8,   1),
+  (9,   1),
+  (10,  1),
+  (11,  1),
+  (12,  1),
+  (13,  1),
+  (14,  1),
+  (15,  1),
+  (16,  1),
+  (17,  1),
+  (18,  1),
+  (19,  1),
+  (20,  1),
+  (21,  2),
+  (22,  2),
+  (23,  2),
+  (24,  2),
+  (25,  2),
+  (26,  2),
+  (27,  2),
+  (28,  2),
+  (29,  2),
+  (30,  2),
+  (31,  2),
+  (32,  2),
+  (33,  2),
+  (34,  2),
+  (35,  2),
+  (36,  2),
+  (37,  2);
+ANALYZE TABLE t;