Wrong result (missing rows) upon condition pushdown on table with DESC key

CREATE TABLE t (a INT, b INT, KEY(b DESC));

INSERT INTO t VALUES (2,8),(9,1),(4,6);

SELECT a, b FROM t GROUP BY b HAVING b != 0 ORDER BY a;

set optimizer_switch = 'condition_pushdown_from_having=off';

SELECT a, b FROM t GROUP BY b HAVING b != 0 ORDER BY a;

DROP TABLE t;

SELECT a, b FROM t GROUP BY b HAVING b != 0 ORDER BY a;

a	b

set optimizer_switch = 'condition_pushdown_from_having=off';

SELECT a, b FROM t GROUP BY b HAVING b != 0 ORDER BY a;

a	b

2	8

4	6

9	1

ANALYZE FORMAT=JSON SELECT a, b FROM t GROUP BY b HAVING b != 0 ORDER BY a;

ANALYZE

{

  "query_optimization": {

    "r_total_time_ms": 0.631530132

  },

  "query_block": {

    "select_id": 1,

    "cost": 0.005628033,

    "r_loops": 1,

    "r_total_time_ms": 0.210688036,

    "filesort": {

      "sort_key": "t.a",

      "r_loops": 1,

      "r_total_time_ms": 0.048360241,

      "r_used_priority_queue": false,

      "r_output_rows": 0,

      "r_buffer_size": "320",

      "r_sort_mode": "sort_key,rowid",

      "temporary_table": {

        "nested_loop": [

          {

            "table": {

              "table_name": "t",

              "access_type": "range",

              "possible_keys": ["b"],

              "key": "b",

              "key_length": "5",

              "loops": 1,

              "r_loops": 1,

              "rows": 3,

              "r_index_rows": 0,

              "r_rows": 0,

              "cost": 0.005628033,

              "r_table_time_ms": 0.034859331,

              "r_other_time_ms": 0.061537373,

              "r_engine_stats": {},

              "filtered": 100,

              "r_total_filtered": 100,

              "index_condition": "t.b <> 0",

              "r_icp_filtered": 0,

              "r_filtered": 100

            }

          }

        ]

      }

    }

  }

}

commit 7e4233746e28cf33a24d6d61e31b82f9838d635d

Author: Dave Gosselin

Date:   Mon Feb 10 13:56:25 2025 -0500

    MDEV-34413 Index Condition Pushdown for reverse ordered scans