fix(runaway): ensure DistSQLContext's checker is synchronized with session variables

[JmPotato]

What problem does this PR solve?

Issue Number: close #61899.

What changed and how does it work?

Update GetDistSQLCtx to check and align the RunawayChecker in the cached DistSQL context with the session's current value.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Prepare:

create table t1(a int, b int);
insert into t1 value(rand()*1000, rand()*1000); x 44600

mysql> select count(*) from t1;
+----------+
| count(*) |
+----------+
|    44600 |
+----------+
1 row in set (0.01 sec)

mysql> CREATE RESOURCE GROUP IF NOT EXISTS rg1 RU_PER_SEC = 100 QUERY_LIMIT=(RU=10, ACTION=KILL);
Query OK, 0 rows affected (0.06 sec)

mysql> SET RESOURCE GROUP rg1;
Query OK, 0 rows affected (0.00 sec)

Before:

mysql> explain analyze select * from t1 where b > 36;
ERROR 8253 (HY000): Query execution was interrupted, identified as runaway query [RequestUnit = RRU:13.419626, WRU:0.000000, WaitDuration:0s(10)]

mysql> explain analyze select min(a)+10 from t1 where a < 639;
ERROR 8253 (HY000): Query execution was interrupted, identified as runaway query [RequestUnit = RRU:38.330615, WRU:0.000000, WaitDuration:0s(10)]

mysql> explain analyze select * from t1 where b > (select min(a)+3 from t1 where a < 452);
+--------------------------+----------+---------+-----------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------+----------+------+
| id                       | estRows  | actRows | task      | access object | execution info                                                                                                                                                                                                                                                                                                                                                                                                                            | operator info                                    | memory   | disk |
+--------------------------+----------+---------+-----------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------+----------+------+
| TableReader_36           | 18466.67 | 44437   | root      |               | time:217.3ms, loops:46, RU:78.809008, cop_task: {num: 9, max: 121.4ms, min: 572.6µs, avg: 24.1ms, p95: 121.4ms, max_proc_keys: 17376, p95_proc_keys: 17376, tot_proc: 25.1ms, tot_wait: 370.2µs, copr_cache_hit_ratio: 0.00, build_task_duration: 8.17µs, max_distsql_concurrency: 1}, rpc_info:{Cop:{num_rpc:9, total_time:217.1ms}}                                                                                                     | data:Selection_35                                | 414.5 KB | N/A  |
| └─Selection_35           | 18466.67 | 44437   | cop[tikv] |               | tikv_task:{proc max:8ms, min:0s, avg: 2.78ms, p80:6ms, p95:8ms, iters:79, tasks:9}, scan_detail: {total_process_keys: 44600, total_process_keys_size: 1906316, total_keys: 44609, get_snapshot_time: 199µs, rocksdb: {key_skipped_count: 44600, block: {cache_hit_count: 93}}}, time_detail: {total_process_time: 25.1ms, total_suspend_time: 45.2µs, total_wait_time: 370.2µs, total_kv_read_wall_time: 25ms, tikv_wall_time: 26.2ms}    | gt(test.t1.b, 3)                                 | N/A      | N/A  |
|   └─TableFullScan_34     | 55400.00 | 44600   | cop[tikv] | table:t1      | tikv_task:{proc max:8ms, min:0s, avg: 2.78ms, p80:6ms, p95:8ms, iters:79, tasks:9}                                                                                                                                                                                                                                                                                                                                                        | keep order:false, stats:partial[b:unInitialized] | N/A      | N/A  |
+--------------------------+----------+---------+-----------+---------------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------+----------+------+
3 rows in set (0.24 sec)

After:

mysql> explain analyze select min(a)+10 from t1 where a < 639;
ERROR 8253 (HY000): Query execution was interrupted, identified as runaway query [RequestUnit = RRU:29.563074, WRU:0.000000, WaitDuration:0s(10)]

mysql> explain analyze select * from t1 where b > 36;
ERROR 8253 (HY000): Query execution was interrupted, identified as runaway query [RequestUnit = RRU:10.572321, WRU:0.000000, WaitDuration:0s(10)]

mysql> explain analyze select * from t1 where b > (select min(a)+3 from t1 where a < 452);
ERROR 8253 (HY000): Query execution was interrupted, identified as runaway query [RequestUnit = RRU:30.184085, WRU:0.000000, WaitDuration:0s(10)]

Release note

Fixed an issue where the evaluating of non-correlated subqueries could cause runaway configuration to become invalid.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.7239%. Comparing base (43c7806) to head (ccefab8).
Report is 12 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #61907        +/-   ##
================================================
+ Coverage   73.0244%   73.7239%   +0.6994%     
================================================
  Files          1735       1735                
  Lines        481425     484380      +2955     
================================================
+ Hits         351558     357104      +5546     
+ Misses       108336     105740      -2596     
- Partials      21531      21536         +5     

Flag	Coverage Δ
integration	42.5868% <100.0000%> (?)
unit	72.6025% <100.0000%> (+0.3447%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.7804% <ø> (ø)
parser	∅ <ø> (∅)
br	47.0243% <ø> (+0.4774%)	⬆️

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lhy1024, okJiang, xhebox

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-06-23 03:17:19.029390052 +0000 UTC m=+673691.752569035: ☑️ agreed by okJiang.
• 2025-06-23 16:06:25.64626348 +0000 UTC m=+719838.369442460: ☑️ agreed by xhebox.

[JmPotato]

/cherry-pick release-8.5

[ti-chi-bot]

@JmPotato: new pull request created to branch release-8.5: #62220.

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/cherry-pick release-8.5

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[JmPotato]

/cherry-pick release-7.5

[ti-chi-bot]

@JmPotato: new pull request created to branch release-7.5: #62319.
But this PR has conflicts, please resolve them!

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In response to this:

/cherry-pick release-7.5

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