MDEV-22599 WITHOUT OVERLAPS does not work with prefix indexes

cmp_max is used instead of cmp to compare key_parts

mysql-test/suite/period/r/overlaps.result

@@ -185,6 +185,7 @@ id	u	s	e
 5	6	2003-05-01	2003-07-01
 7	8	2003-05-01	2003-07-01
 9	10	2003-05-01	2003-07-01
+drop sequence seq;
 create or replace table t(id int, s date, e date,
 period for p(s,e));
 insert into t values (1, '2003-01-01', '2003-03-01'),
@@ -281,4 +282,18 @@ Warnings:
 Warning	1062	Duplicate entry '1-2020-03-05-2020-03-01' for key 'x'
 load data infile 'tmp_t.txt' replace into table t;
 ERROR 42000: This version of MariaDB doesn't yet support 'WITHOUT OVERLAPS'
-create or replace database test;
+# MDEV-22599 WITHOUT OVERLAPS does not work with prefix indexes
+create or replace table t1 (a varchar(6), s timestamp, e timestamp,
+period for p(s,e),
+unique(a(3), p without overlaps));
+insert into t1 values ('foo', '2012-01-01', '2015-12-31');
+insert into t1 values ('foobar', '2013-01-01', '2014-01-01');
+ERROR 23000: Duplicate entry 'foo-2014-01-01 00:00:00-2013-01-01 00:00:00' for key 'a'
+insert into t1 values ('bar', '2012-01-01', '2015-12-31'),
+('baz', '2013-01-01', '2014-01-01');
+select * from t1;
+a	s	e
+foo	2012-01-01 00:00:00	2015-12-31 00:00:00
+bar	2012-01-01 00:00:00	2015-12-31 00:00:00
+baz	2013-01-01 00:00:00	2014-01-01 00:00:00
+drop table t, t1;

mysql-test/suite/period/t/overlaps.test

@@ -163,6 +163,7 @@ update t set id= nextval(seq), u= nextval(seq), s='2003-05-01', e='2003-07-01'
 
 --sorted_result
 select * from t;
+drop sequence seq;
 
 create or replace table t(id int, s date, e date,
                           period for p(s,e));
@@ -270,4 +271,18 @@ load data infile 'tmp_t.txt' replace into table t;
 
 remove_file $MYSQLD_DATADIR/test/tmp_t.txt;
 
-create or replace database test;
+
+--echo # MDEV-22599 WITHOUT OVERLAPS does not work with prefix indexes
+create or replace table t1 (a varchar(6), s timestamp, e timestamp,
+                            period for p(s,e),
+                            unique(a(3), p without overlaps));
+
+insert into t1 values ('foo', '2012-01-01', '2015-12-31');
+--error ER_DUP_ENTRY
+insert into t1 values ('foobar', '2013-01-01', '2014-01-01');
+
+insert into t1 values ('bar', '2012-01-01', '2015-12-31'),
+                      ('baz', '2013-01-01', '2014-01-01');
+select * from t1;
+
+drop table t, t1;

sql/table.cc

@@ -8759,7 +8759,8 @@ bool TABLE::check_period_overlaps(const KEY &key,
     if (key.key_part[part_nr].null_bit)
       if (f->is_null_in_record(lhs) || f->is_null_in_record(rhs))
         return false;
-    if (f->cmp(f->ptr_in_record(lhs), f->ptr_in_record(rhs)) != 0)
+    uint kp_len= key.key_part[part_nr].length;
+    if (f->cmp_max(f->ptr_in_record(lhs), f->ptr_in_record(rhs), kp_len) != 0)
       return false;
   }