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TiFlash plan returns No access path error in RC isolation level #65059

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#65127
Closed
TiFlash plan returns No access path error in RC isolation level#65059
#65127
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hawkingrei
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affects-8.5This bug affects the 8.5.x(LTS) versions.component/tiflashreport/customerCustomers have encountered this bug.sig/plannerSIG: Plannertype/questionThe issue belongs to a question.

Description

@pcqz7
pcqz7
opened on Dec 16, 2025

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table t1(a int primary key, b int);
create table t2(a int primary key, b int);
alter table t1 set tiflash replica 1;
alter table t2 set tiflash replica 1;
set tx_isolation="READ-COMMITTED";
begin;
explain select /*+ set_var(tidb_isolation_read_engines='tidb,tiflash'),set_var(tidb_enforce_mpp=on) */ * from t1 join t2 on t1.a=t2.b where t1.a in (1,2);

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

TiFlash plan is shown without error.

3. What did you see instead (Required)

ERROR 1815 (HY000): Internal : No access path for table 't1' is found with 'tidb_isolation_read_engines' = 'tidb,tiflash', valid values can be 'tikv'.

4. What is your TiDB version? (Required)

v8.5.1

Activity

  1. pcqz7
    added
    type/bugThe issue is confirmed as a bug.
    on Dec 16, 2025

  2. pcqz7 commented on Dec 16, 2025

    @pcqz7
    pcqz7
    on Dec 16, 2025
    Author

    /report customer

  3. ti-chi-bot
    added
    report/customerCustomers have encountered this bug.
    on Dec 16, 2025
  4. jebter
    added
    component/tiflash
    on Dec 16, 2025

  5. pcqz7 commented on Dec 16, 2025

    @pcqz7
    pcqz7
    on Dec 16, 2025
    Author

    The error could be an expected behavior after the fix #39543, but TiFlash supports RC isolation level that's not exactly the same as for update.

  6. elsa0520 commented on Dec 16, 2025

    @elsa0520
    elsa0520
    on Dec 16, 2025
    Contributor

    I try to reproduce this problem and I found
    If query the t1 without where predicate, it is ok.

    mysql> explain  select  /*+ set_var(tidb_isolation_read_engines='tidb,tiflash'),set_var(tidb_enforce_mpp=on) */ * from t1 ;
+-------------------------+----------+--------------+---------------+--------------------------------------+
| id                      | estRows  | task         | access object | operator info                        |
+-------------------------+----------+--------------+---------------+--------------------------------------+
| TableReader_10          | 10000.00 | root         |               | MppVersion: 2, data:ExchangeSender_9 |
| └─ExchangeSender_9      | 10000.00 | mpp[tiflash] |               | ExchangeType: PassThrough            |
|   └─TableFullScan_8     | 10000.00 | mpp[tiflash] | table:t1      | keep order:false, stats:pseudo       |
+-------------------------+----------+--------------+---------------+--------------------------------------+
3 rows in set (0.00 sec)

    But if query the t1 with where predicate, it is error

    mysql> explain  select  /*+ set_var(tidb_isolation_read_engines='tidb,tiflash'),set_var(tidb_enforce_mpp=on) */ * from t1 where t1.a in (1,2);
ERROR 1815 (HY000): Internal : No access path for table 't1' is found with 'tidb_isolation_read_engines' = 'tidb,tiflash', valid values can be 'tikv'.

  7. elsa0520 commented on Dec 16, 2025

    @elsa0520
    elsa0520
    on Dec 16, 2025
    Contributor

    If the query is inside of transaction, it failed.

    So the trigger condition are:

    1. In the RC isolation level: begin transaction
    2. Query the table with primary key condition : can short path to batch point get
    mysql> explain  select  /*+ set_var(tidb_isolation_read_engines='tidb,tiflash'),set_var(tidb_enforce_mpp=on) */ * from t1 where t1.a in (1,2);
+--------------------------+---------+--------------+---------------+----------------------------------------------------+
| id                       | estRows | task         | access object | operator info                                      |
+--------------------------+---------+--------------+---------------+----------------------------------------------------+
| TableReader_11           | 2.00    | root         |               | MppVersion: 2, data:ExchangeSender_10              |
| └─ExchangeSender_10      | 2.00    | mpp[tiflash] |               | ExchangeType: PassThrough                          |
|   └─TableRangeScan_9     | 2.00    | mpp[tiflash] | table:t1      | range:[1,1], [2,2], keep order:false, stats:pseudo |
+--------------------------+---------+--------------+---------------+----------------------------------------------------+
3 rows in set (0.00 sec)

mysql> begin;
Query OK, 0 rows affected (0.00 sec)

mysql> explain  select  /*+ set_var(tidb_isolation_read_engines='tidb,tiflash'),set_var(tidb_enforce_mpp=on) */ * from t1 where t1.a in (1,2);
ERROR 1815 (HY000): Internal : No access path for table 't1' is found with 'tidb_isolation_read_engines' = 'tidb,tiflash', valid values can be 'tikv'.
  8. elsa0520
    added
    sig/plannerSIG: Planner
    type/questionThe issue belongs to a question.
    and removed
    type/bugThe issue is confirmed as a bug.
    on Dec 16, 2025

  9. pcqz7 commented on Dec 16, 2025

    @pcqz7
    pcqz7
    on Dec 16, 2025
    Author

    After the fix #39553, the error is reported

    mysql> create table t1(a int primary key, b int);
Query OK, 0 rows affected (0.12 sec)

mysql> create table t2(a int primary key, b int);
Query OK, 0 rows affected (0.11 sec)

mysql> alter table t1 set tiflash replica 1;
Query OK, 0 rows affected (0.11 sec)

mysql> alter table t2 set tiflash replica 1;
Query OK, 0 rows affected (0.10 sec)

mysql> set tx_isolation="READ-COMMITTED";
Query OK, 0 rows affected (0.00 sec)

mysql> begin;
Query OK, 0 rows affected (0.00 sec)

mysql> explain select /*+ set_var(tidb_isolation_read_engines='tidb,tiflash'),set_var(tidb_enforce_mpp=on) */ * from t1 join t2 on t1.a=t2.b where t1.a in (1,2);
+---------------------------------+----------+--------------+---------------+----------------------------------------------+
| id                              | estRows  | task         | access object | operator info                                |
+---------------------------------+----------+--------------+---------------+----------------------------------------------+
| HashJoin_21                     | 2.50     | root         |               | inner join, equal:[eq(test.t1.a, test.t2.b)] |
| ├─Batch_Point_Get_28(Build)     | 2.00     | root         | table:t1      | handle:[1 2], keep order:false, desc:false   |
| └─TableReader_27(Probe)         | 20.00    | root         |               | data:Selection_26                            |
|   └─Selection_26                | 20.00    | cop[tiflash] |               | in(test.t2.b, 1, 2), not(isnull(test.t2.b))  |
|     └─TableFullScan_25          | 10000.00 | cop[tiflash] | table:t2      | keep order:false, stats:pseudo               |
+---------------------------------+----------+--------------+---------------+----------------------------------------------+
5 rows in set, 4 warnings (0.00 sec)

mysql> show warnings;
+---------+------+--------------------------------------------------------------------------+
| Level   | Code | Message                                                                  |
+---------+------+--------------------------------------------------------------------------+
| Warning | 3637 | Variable 'tidb_isolation_read_engines' cannot be set using SET_VAR hint. |
| Warning | 3637 | Variable 'tidb_enforce_mpp' cannot be set using SET_VAR hint.            |
| Warning | 3637 | Variable 'tidb_isolation_read_engines' cannot be set using SET_VAR hint. |
| Warning | 3637 | Variable 'tidb_enforce_mpp' cannot be set using SET_VAR hint.            |
+---------+------+--------------------------------------------------------------------------+
4 rows in set (0.00 sec)

mysql> set tidb_isolation_read_engines='tidb,tiflash';
Query OK, 0 rows affected (0.00 sec)

mysql> set tidb_enforce_mpp=on;
Query OK, 0 rows affected (0.00 sec)

mysql> explain select /*+ set_var(tidb_isolation_read_engines='tidb,tiflash'),set_var(tidb_enforce_mpp=on) */ * from t1 join t2 on t1.a=t2.b where t1.a in (1,2);
ERROR 1815 (HY000): Internal : No access path for table 't1' is found with 'tidb_isolation_read_engines' = 'tidb,tiflash', valid values can be 'tikv'.
mysql> select tidb_version();
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v6.5.0-alpha-274-g35319e8
Edition: Community
Git Commit Hash: 35319e8f2a237b548326cc97fe99fb8d72b81385
Git Branch: HEAD
UTC Build Time: 2025-12-16 09:54:27
GoVersion: go1.19.9
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: tikv |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
  10. hawkingrei
    self-assigned this
    on Dec 18, 2025
  11. ti-chi-bot
    closed this as completedin #65127on Dec 29, 2025
  12. hawkingrei
    added a commit that references this issue on Dec 29, 2025

    planner: fix no access path when TiKV read is disabled under RC isola…

    1776433
  13. Reminiscent
    added a commit that references this issue on Jan 14, 2026

    planner: fix no access path when TiKV read is disabled under RC isola…

    084304b
  14. qw4990
    added
    affects-8.5This bug affects the 8.5.x(LTS) versions.
    on Mar 10, 2026
  15. ti-chi-bot
    added a commit that references this issue on Mar 17, 2026

    planner: fix no access path when TiKV read is disabled under RC isola…

    e6de890
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