planner: tolerate reasonable time lag between different TiDB nodes when updating binding cache (#64289)

[qw4990]

This is an automated cherry-pick of #64289

What problem does this PR solve?

Issue Number: close #64250

Problem Summary: planner: tolerate reasonable time lag between different TiDB nodes when updating binding cache

What changed and how does it work?

When updating binding cache, TiDB doesn't consider time lag between different nodes, which could cause inconsistency on binding cache. See more info in #64250.

Below is an simplified example, TiDB1's clock is consistent with the real time, while TiDB2's clock is 0.5s slower than the real time:

Real Physical Time	Action of TiDB1	Action of TiDB2
t1 00:00:30.200000	create the new binding, write it into mysql.bind_info with timestamp 00:00:30.200000	-
t2 00:00:30.300000	update binding cache: 1) load latest binding from mysql.bind_info where binding.update_time > LAST_UPDATE_TIME, 2) set LAST_UPDATE_TIME to the latest binding.update_time, in this case its 00:00:30.200000	-
t3 00:00:30.500000	-	create a new binding with timestamp 00:00:30.000000 due to system lock issue
t4 00:00:30.600000	-	update its binding cache
t5 00:01:00.000000	update binding cache, can't see the binding crated by TiDB2 ❌	-

In the case above, TiDB1 can never see the binding created by TiDB2 with timestamp 00:00:30.000000 because its LAST_UPDATE_TIME = 00:00:30.200000 is larger than that binding's timestamp.

The solution is simple, set a tolerance interval (10s by default) when updating binding cache. And it's safe to load duplicated bindings, because we'll deduplicate them before actually putting them into the cache.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[tiprow]

Hi @qw4990. Thanks for your PR.

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[elsa0520]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-11-07 10:47:49.531067825 +0000 UTC m=+439918.974097694: ☑️ agreed by winoros.
• 2025-11-07 10:49:07.50622045 +0000 UTC m=+439996.949250329: ☑️ agreed by elsa0520.

[codecov]

Codecov Report

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[hawkingrei]

/retest

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: elsa0520, hawkingrei, winoros

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[hawkingrei]

/retest

[ti-chi-bot]

@qw4990: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	1498c4a	link	true	/test unit-test

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