Added test [#METR-22032].

dbms/tests/queries/0_stateless/00345_index_signed_unsigned_comparison.reference

+1	1	2016-07-07
+-1	-1	2016-07-07
+1	1	2016-07-07
+-1	-1	2016-07-07

dbms/tests/queries/0_stateless/00345_index_signed_unsigned_comparison.sql

+DROP TABLE IF EXISTS test.index;
+
+CREATE TABLE test.index
+(
+    key Int32,
+    name String,
+    merge_date Date
+) ENGINE = MergeTree(merge_date, key, 8192);
+
+insert into test.index values (1,'1','2016-07-07');
+insert into test.index values (-1,'-1','2016-07-07');
+
+select * from test.index where key = 1;
+select * from test.index where key = -1;
+OPTIMIZE TABLE test.index;
+select * from test.index where key = 1;
+select * from test.index where key = -1;
+
+DROP TABLE test.index;