MDEV-26938 Support descending indexes internally in InnoDB (server part)

* preserve DESC index property in the parser
* store it in the frm (only for HA_KEY_ALG_BTREE)
* read it from the frm
* show it in SHOW CREATE
* skip DESC indexes in opt_range.cc and opt_sum.cc
* ORDER BY test

This includes a fix of MDEV-27432.

1 files changed, 9 insertions, 5 deletions

diff --git a/mysql-test/main/partition_order.test b/mysql-test/main/partition_order.test
index ad956361d00..f5cd4c25074 100644
--- a/mysql-test/main/partition_order.test
+++ b/mysql-test/main/partition_order.test
@@ -1,14 +1,9 @@
-#--disable_abort_on_error
 #
 # Simple test for the partition storage engine
 # Focuses on tests of ordered index read
 # 
 -- source include/have_partition.inc
 
---disable_warnings
-drop table if exists t1;
---enable_warnings
-
 #
 # Ordered index read, int type
 #
@@ -842,3 +837,12 @@ INSERT into t1 values (1, NULL, NULL), (2, NULL, '10');
 select * from t1 where a = 1 order by a desc, b desc;
 select * from t1 where a = 1 order by b desc;
 drop table t1;
+
+--echo #
+--echo # MDEV-13756 Implement descending index: KEY (a DESC, b ASC)
+--echo #
+create table t1 (a int, b int, key(a desc)) partition by hash(a) partitions 4;
+insert into t1 values (1,1),(2,2),(3,3),(4,4),(5,5),(6,6);
+explain select * from t1 order by a limit 3;
+select * from t1 order by a limit 3;
+drop table t1;