unexpected full range scan

[lmduean]

Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)
CREATE TABLE t71706696 (
  dt char(8) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL,
  db_id bigint(20) NOT NULL,
  tbl_id bigint(20) NOT NULL,
  db_name varchar(200) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL,
  UNIQUE KEY dt_2 (dt, db_id, tbl_id)
);

explain
select
  *
from
  t71706696 force index(dt_2)
where
  (
    (
      dt = '20210112'
      and db_id = '62812'
      and tbl_id > '228892694'
    )
    or (
      dt = '20210112'
      and db_id = '62813'
      and tbl_id <= '226785696'
    )
    or (
      dt = '20210112'
      and db_id > '62812'
      and db_id < '62813'
    )
  )

2. What did you expect to see? (Required)

+-------------------------------+---------+-----------+------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------+
| id                            | estRows | task      | access object                                  | operator info                                                                                                                                |
+-------------------------------+---------+-----------+------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------+
| IndexLookUp_7                 | 0.67    | root      |                                                |                                                                                                                                              |
| ├─IndexRangeScan_5(Build)     | 0.67    | cop[tikv] | table:t71706696, index:dt_2(dt, db_id, tbl_id) | range:("20210112" 62812 228892694,"20210112" 62812 +inf], ["20210112" 62813 -inf,"20210112" 62813 226785696], keep order:false, stats:pseudo |
| └─TableRowIDScan_6(Probe)     | 0.67    | cop[tikv] | table:t71706696                                | keep order:false, stats:pseudo                                                                                                               |
+-------------------------------+---------+-----------+------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec

3. What did you see instead (Required)

+-------------------------------+----------+-----------+------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| id                            | estRows  | task      | access object                                  | operator info                                                                                                                                                                                |
+-------------------------------+----------+-----------+------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| IndexLookUp_8                 | 0.67     | root      |                                                |                                                                                                                                                                                |
| ├─Selection_7(Build)          | 0.67     | cop[tikv] |                                                | or(and(eq(test.t71706696.dt, "20210112"), and(eq(test.t71706696.db_id, 62812), gt(test.t71706696.tbl_id, 228892694))), or(and(eq(test.t71706696.dt, "20210112"), and(eq(test.t71706696.db_id, 62813), le(test.t71706696.tbl_id, 226785696))), and(eq(test.t71706696.dt, "20210112"), and(gt(test.t71706696.db_id, 62812), lt(test.t71706696.db_id, 62813))))) |
| │ └─IndexFullScan_5           | 10000.00 | cop[tikv] | table:t71706696, index:dt_2(dt, db_id, tbl_id) | keep order:false, stats:pseudo                                                                                                                                                                                |
| └─TableRowIDScan_6(Probe)     | 0.67     | cop[tikv] | table:t71706696                                | keep order:false, stats:pseudo                                                                                                                                                                                |
+-------------------------------+----------+-----------+------------------------------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

4. What is your TiDB version? (Required)

master
Release Version: v6.6.0-alpha-349-g07af605381-dirty
Edition: Community
Git Commit Hash: 07af605
Git Branch: HEAD
UTC Build Time: 2023-02-02 09:18:25
GoVersion: go1.19.3
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: unistore

possible fix:

diff --git a/util/ranger/detacher.go b/util/ranger/detacher.go
index 606f53c402..e49cac8030 100644
--- a/util/ranger/detacher.go
+++ b/util/ranger/detacher.go
@@ -678,6 +678,10 @@ func (d *rangeDetacher) detachDNFCondAndBuildRangeForIndex(condition *expression
                        ranges := res.Ranges
                        accesses = res.AccessConds
                        filters = res.RemainedConds
+                       // If dnf item evaluate to false always, ignore it
+                       if len(ranges) == 0 {
+                               continue
+                       }
                        if len(accesses) == 0 {
                                return FullRange(), nil, nil, true, nil
                        }