MDEV-10844: EXPLAIN FORMAT=JSON doesn't show order direction for filesort

Currently explain format=json does not show the order direction of fields used during filesort.
This patch would remove this limitation

3 files changed, 72 insertions, 1 deletions

diff --git a/mysql-test/r/explain_json.result b/mysql-test/r/explain_json.result
index b83334c8b08..db792f4f2b6 100644
--- a/mysql-test/r/explain_json.result
+++ b/mysql-test/r/explain_json.result
@@ -1582,3 +1582,63 @@ EXPLAIN
   }
 }
 drop table t0,t1;
+#
+# MDEV-10844: EXPLAIN FORMAT=JSON doesn't show order direction for filesort
+#
+create table t1 (a int, b int);
+insert into t1 values (1,2),(3,4),(2,3);
+explain format=json select * from t1 order by a, b desc;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "read_sorted_file": {
+      "filesort": {
+        "sort_key": "t1.a, t1.b desc",
+        "table": {
+          "table_name": "t1",
+          "access_type": "ALL",
+          "rows": 3,
+          "filtered": 100
+        }
+      }
+    }
+  }
+}
+explain format=json select * from t1 order by a desc, b desc;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "read_sorted_file": {
+      "filesort": {
+        "sort_key": "t1.a desc, t1.b desc",
+        "table": {
+          "table_name": "t1",
+          "access_type": "ALL",
+          "rows": 3,
+          "filtered": 100
+        }
+      }
+    }
+  }
+}
+explain format=json select * from t1 order by a desc, b ;
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "read_sorted_file": {
+      "filesort": {
+        "sort_key": "t1.a desc, t1.b",
+        "table": {
+          "table_name": "t1",
+          "access_type": "ALL",
+          "rows": 3,
+          "filtered": 100
+        }
+      }
+    }
+  }
+}
+drop table t1;
diff --git a/mysql-test/r/win.result b/mysql-test/r/win.result
index cfe3ebe6a3c..7e0c86b1668 100644
--- a/mysql-test/r/win.result
+++ b/mysql-test/r/win.result
@@ -1779,7 +1779,7 @@ EXPLAIN
   "query_block": {
     "select_id": 1,
     "filesort": {
-      "sort_key": "row_number() over ( order by t1.s1,t1.s2)",
+      "sort_key": "row_number() over ( order by t1.s1,t1.s2) desc",
       "window_functions_computation": {
         "sorts": {
           "filesort": {
diff --git a/mysql-test/t/explain_json.test b/mysql-test/t/explain_json.test
index d253b8380e9..c3665b1818b 100644
--- a/mysql-test/t/explain_json.test
+++ b/mysql-test/t/explain_json.test
@@ -406,3 +406,14 @@ explain format=json
 select a, (select max(a) from t1 where t0.a<5 and t1.b<t0.a) from t0;
 drop table t0,t1;
 
+--echo #
+--echo # MDEV-10844: EXPLAIN FORMAT=JSON doesn't show order direction for filesort
+--echo #
+
+create table t1 (a int, b int);
+insert into t1 values (1,2),(3,4),(2,3);
+explain format=json select * from t1 order by a, b desc;
+explain format=json select * from t1 order by a desc, b desc;
+explain format=json select * from t1 order by a desc, b ;
+drop table t1;
+