*: implement shared lock for foreign key by you06 · Pull Request #65752 · pingcap/tidb

you06 · 2026-01-23T07:17:36Z

What problem does this PR solve?

Issue Number: close #66154

ref tikv/tikv#19087

Problem Summary:

What changed and how does it work?

Add shared lock support in TiDB.

Introduce a new variable tidb_foreign_key_check_in_shared_lock as the feature switch, default off.
Mark exclusive or shared flags during execution
Some stats and execution details for shared lock.

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

Release note

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

Support shared locks in foreign key use cases.

tiprow · 2026-01-23T07:17:50Z

Hi @you06. Thanks for your PR.

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Copilot

Pull request overview

This PR introduces shared-lock support for foreign key checks in TiDB and wires basic observability for shared locks.

Changes:

Add a new session/global system variable tidb_foreign_key_check_in_shared_lock and associated session fields to control whether foreign key checks use shared locks.
Extend the pessimistic DML locking path and foreign key checker to distinguish between exclusive and shared “unchanged” keys, defer FK locks into handlePessimisticDML, and propagate a new InShareMode flag down to the TiKV lock RPCs and coprocessor lock resolution.
Add shared-lock-related execution details and metrics (SharedLockKeysDetail, StatementSharedLockKeysCount) and expose them via Prometheus and a new Grafana panel, plus basic integration into runtime stats.

Reviewed changes

Copilot reviewed 18 out of 19 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
`pkg/util/execdetails/runtime_stats.go`	Adds `SharedLockKeys` to `RuntimeStatsWithCommit` so commit/runtime stats can carry shared-lock execution details.
`pkg/util/execdetails/execdetails.go`	Extends `ExecDetails`/`SyncExecDetails` with `SharedLockKeysDetail`, `LockKeysDuration`, and a `MergeSharedLockKeysExecDetails` helper.
`pkg/store/copr/coprocessor.go`	Updates coprocessor lock error handling to resolve either a single lock or a set of shared locks via `LockInfo.GetSharedLockInfos()`.
`pkg/sessionctx/variable/sysvar.go`	Registers the new `tidb_foreign_key_check_in_shared_lock` sysvar and plumbs it into `SessionVars`.
`pkg/sessionctx/variable/session.go`	Changes `TxnCtxNoNeedToRestore.unchangedKeys` to `map[string]bool` and adds helpers to record and split unchanged keys into exclusive vs shared lock sets; adds `ForeignKeyCheckInSharedLock` to `SessionVars`.
`pkg/sessionctx/vardef/tidb_vars.go`	Defines the name and default (`false`) for `TiDBForeignKeyCheckInSharedLock`.
`pkg/sessionctx/stmtctx/stmtctx.go`	Extends `StatementContext` with counters/durations for pessimistic locking, including `SharedLockKeysCount`.
`pkg/metrics/session.go`	Introduces the `StatementSharedLockKeysCount` histogram for counting keys locked in shared mode per statement.
`pkg/metrics/metrics.go`	Registers the new `StatementSharedLockKeysCount` Prometheus metric.
`pkg/metrics/grafana/tidb.json`	Adds a Grafana heatmap panel that visualizes the distribution of `statement_shared_lock_keys_count`.
`pkg/executor/write.go`	Updates unchanged-key tracking for row/unique keys to mark them as exclusive (`shared=false`) in the new `AddUnchangedKeyForLock` API.
`pkg/executor/select.go`	Extends `newLockCtx` to accept an `inSharedMode` flag and propagate it to `LockCtx.InShareMode`; adjusts callers accordingly.
`pkg/executor/point_get.go`	Adapts point get pessimistic locking to the new `newLockCtx(..., inSharedMode bool)` signature (currently always false).
`pkg/executor/insert_common.go`	Marks duplicate-key unchanged locks as exclusive via the new `AddUnchangedKeyForLock(key, false)` signature.
`pkg/executor/foreign_key.go`	Changes FK check locking: for pessimistic txns, collects keys into `TxnCtx.unchangedKeys` as shared; for optimistic txns, continues to lock immediately using `newLockCtx(..., false)`.
`pkg/executor/batch_point_get.go`	Updates batch point get pessimistic locking to the new `newLockCtx` signature.
`pkg/executor/adapter.go`	Refactors `handlePessimisticDML` to reset and then split unchanged keys into exclusive vs shared passes, honoring `ForeignKeyCheckInSharedLock`; records shared-lock metrics and attaches `SharedLockKeys` exec details into runtime stats.
`go.mod`	Bumps `github.com/tikv/pd/client` version, promotes some AliCloud dependencies to direct, and adds a `replace` to use `github.com/you06/client-go/v2` for `github.com/tikv/client-go/v2`.
`go.sum`	Synchronizes module checksums with the updated `go.mod` (including the new client-go fork and pd client version).

pkg/executor/adapter.go

pkg/metrics/grafana/tidb.json

pkg/util/execdetails/runtime_stats.go

pkg/executor/adapter.go

you06 · 2026-01-28T08:23:30Z

/retest

tiprow · 2026-01-28T08:23:54Z

@you06: PRs from untrusted users cannot be marked as trusted with /ok-to-test in this repo meaning untrusted PR authors can never trigger tests themselves. Collaborators can still trigger tests on the PR using /test.

Details

In response to this:

/retest

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Signed-off-by: you06 <you1474600@gmail.com>

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Signed-off-by: you06 <you1474600@gmail.com>

you06 · 2026-02-10T05:53:58Z

/retest

cfzjywxk · 2026-02-10T07:02:37Z

/retest

Signed-off-by: you06 <you1474600@gmail.com>

you06 · 2026-02-10T11:18:23Z

/retest

you06 · 2026-02-10T12:34:36Z

/retest

you06 · 2026-02-10T14:20:24Z

/retest

Signed-off-by: you06 <you1474600@gmail.com>

you06 · 2026-02-11T02:40:38Z

/retest

Signed-off-by: you06 <you1474600@gmail.com>

ti-chi-bot · 2026-02-11T04:15:28Z

[LGTM Timeline notifier]

Timeline:

2026-02-09 08:55:55.116919513 +0000 UTC m=+175170.811059353: ☑️ agreed by cfzjywxk.
2026-02-11 04:15:27.255786887 +0000 UTC m=+331142.949926737: ☑️ agreed by zyguan.

hawkingrei · 2026-02-11T05:20:55Z

/retest

yudongusa

Please open a document PR

pkg/metrics/grafana/tidb.json

zimulala

Metrics LGTM

ti-chi-bot · 2026-02-11T08:39:02Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, yudongusa, YuJuncen, zimulala, zyguan

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Needs approval from an approver in each of these files:

~~OWNERS~~ [YuJuncen,cfzjywxk,zimulala,zyguan]
~~br/OWNERS~~ [YuJuncen]
~~pkg/metrics/OWNERS~~ [zimulala]
~~pkg/sessionctx/vardef/OWNERS~~ [yudongusa]
~~pkg/sessionctx/variable/OWNERS~~ [yudongusa]

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hawkingrei · 2026-02-11T10:45:45Z

/retest

hawkingrei · 2026-02-11T11:25:41Z

/retest

Copilot AI review requested due to automatic review settings January 23, 2026 07:17

ti-chi-bot bot added do-not-merge/invalid-title do-not-merge/needs-linked-issue do-not-merge/needs-tests-checked release-note-none Denotes a PR that doesn't merit a release note. size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. labels Jan 23, 2026

you06 changed the title ~~Master shared lock~~ *: implement shared lock for TiDB Jan 23, 2026

ti-chi-bot bot removed the do-not-merge/invalid-title label Jan 23, 2026

Copilot started reviewing on behalf of you06 January 23, 2026 07:17 View session

you06 mentioned this pull request Jan 23, 2026

Support shared lock for foreign key tikv/tikv#19087

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Copilot AI reviewed Jan 23, 2026

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you06-pingcap force-pushed the master-shared-lock branch from a77818d to 4ca8a65 Compare January 27, 2026 08:03

ti-chi-bot bot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. and removed size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. labels Jan 28, 2026

you06 changed the title *: implement shared lock for TiDB *: implement shared lock for foreign key Jan 28, 2026

you06 and others added 10 commits February 9, 2026 12:05

update client-go

14f0ad5

Signed-off-by: you06 <you1474600@gmail.com>

resolve conflict

8fa85e4

Signed-off-by: you06 <you1474600@gmail.com>

resolve shared locks in coprocessor (pingcap#64928)

eae87e3

Signed-off-by: you06 <you1474600@gmail.com>

add to control shared lock usage

6a42375

Signed-off-by: you06 <you1474600@gmail.com>

fix shared lock stats

9be2522

Signed-off-by: you06 <you1474600@gmail.com>

enable shared lock in tests

88be9ca

Signed-off-by: you06 <you1474600@gmail.com>

BAZEL

cf9b036

Signed-off-by: you06 <you1474600@gmail.com>

Apply suggestions from code review

ab8e0a2

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

address comment

959587a

Signed-off-by: you06 <you1474600@gmail.com>

update client-go & bazel

520e7ce

Signed-off-by: you06 <you1474600@gmail.com>

you06-pingcap force-pushed the master-shared-lock branch from dca7e8a to 520e7ce Compare February 9, 2026 03:08

fix go.mod

4dbf793

Signed-off-by: you06 <you1474600@gmail.com>

ti-chi-bot bot added the needs-1-more-lgtm Indicates a PR needs 1 more LGTM. label Feb 9, 2026

fix the test TestSharedLockLockView

2b3e84d

Signed-off-by: you06 <you1474600@gmail.com>

ti-chi-bot bot added the do-not-merge/needs-linked-issue label Feb 9, 2026

fix admin check by split it into multi statements

15cba04

Signed-off-by: you06 <you1474600@gmail.com>

ti-chi-bot bot removed the do-not-merge/needs-linked-issue label Feb 10, 2026

fix lock duration in foreign key check stats

0a12f79

Signed-off-by: you06 <you1474600@gmail.com>

skip shared lock integration test in next-gen build

c2e10fa

Signed-off-by: you06 <you1474600@gmail.com>

address comment

f9ec231

Signed-off-by: you06 <you1474600@gmail.com>

zyguan approved these changes Feb 11, 2026

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ti-chi-bot bot added lgtm and removed needs-1-more-lgtm Indicates a PR needs 1 more LGTM. labels Feb 11, 2026

yudongusa approved these changes Feb 11, 2026

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YuJuncen approved these changes Feb 11, 2026

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zimulala reviewed Feb 11, 2026

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pkg/metrics/grafana/tidb.json Show resolved Hide resolved

zimulala approved these changes Feb 11, 2026

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ti-chi-bot bot added the approved label Feb 11, 2026

ti-chi-bot bot merged commit 94b366e into pingcap:master Feb 11, 2026
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ti-chi-bot bot added release-note Denotes a PR that will be considered when it comes time to generate release notes. and removed release-note-none Denotes a PR that doesn't merit a release note. labels Feb 11, 2026

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you06 commented Jan 23, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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What problem does this PR solve?

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[LGTM Timeline notifier]

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you06 commented Jan 23, 2026 •

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