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Merged
ti-chi-bot merged 5 commits into from
Jul 20, 2026
Merged

Bypass locks invisible to read snapshot (#243) #244

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8275d48
Bypass locks invisible to read snapshot (#243)
windtalker Jul 16, 2026
d667e41
Add lock resolver bypass tests
windtalker Jul 17, 2026
de7c073
Use pushed locks in scanner
windtalker Jul 17, 2026
f6d3fdc
Wait for mock-tikv in build test
windtalker Jul 20, 2026
1e367b1
Resolve locks after marking them bypassable
windtalker Jul 20, 2026
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23 changes: 9 additions & 14 deletions include/pingcap/kv/LockResolver.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,25 +20,20 @@ struct TxnStatus
{
uint64_t ttl = 0;
uint64_t commit_ts = 0;
::kvrpcpb::Action action;
::kvrpcpb::Action action = ::kvrpcpb::Action::NoAction;
std::optional<::kvrpcpb::LockInfo> primary_lock;
bool isCommitted() const { return ttl == 0 && commit_ts > 0; }

bool isRolledBack() const
{
return ttl == 0 && commit_ts == 0
&& (action == kvrpcpb::Action::NoAction || action == kvrpcpb::Action::LockNotExistRollback
|| action == kvrpcpb::Action::TTLExpireRollback);
}

bool isCacheable() const
{
if (isCommitted())
{
return true;
}
if (ttl == 0)
{
if (action == kvrpcpb::Action::NoAction || action == kvrpcpb::Action::LockNotExistRollback
|| action == kvrpcpb::Action::TTLExpireRollback)
{
return true;
}
}
return false;
return isCommitted() || isRolledBack();
}
};

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24 changes: 24 additions & 0 deletions src/kv/LockResolver.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,24 @@ namespace pingcap
{
namespace kv
{
namespace
{
bool canBypassLockForRead(const TxnStatus & status, uint64_t caller_start_ts)
{
if (status.ttl != 0)
return false;

if (status.isCommitted())
return status.commit_ts > caller_start_ts;

// Expired async-commit locks need resolveLockAsync to determine the final status.
if (status.primary_lock.has_value() && status.primary_lock->use_async_commit())
return false;

return status.isRolledBack();
}
} // namespace

std::string Lock::toDebugString() const
{
return "key: " + Redact::keyToDebugString(key) + " primary: " + Redact::keyToDebugString(primary)
Expand Down Expand Up @@ -56,6 +74,12 @@ int64_t LockResolver::resolveLocks(

if (status.ttl == 0)
{
if (!for_write && canBypassLockForRead(status, caller_start_ts))
{
pushed.push_back(lock->txn_id);
break;

@ekexium ekexium Jul 17, 2026

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The lock will not be resolved, so it must be put into resolved_locks to skip it in tikv. However the scanner doesn't use the returned pushed?

@windtalker windtalker Jul 17, 2026

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In client-c, pushed will be treated as min_commit_ts_pushed in

client-c/src/coprocessor/Client.cc

Lines 723 to 727 in 6b91f49

auto before_expired = cluster->lock_resolver->resolveLocks(bo, task.req->start_ts, locks, pushed);
if (!pushed.empty())
{
min_commit_ts_pushed.addTimestamps(pushed);
}

And min_commit_ts_pushed wil be added to add_resolved_locks when constructing request

client-c/src/coprocessor/Client.cc

Lines 705 to 708 in 6b91f49

for (auto ts : min_commit_ts_pushed.getTimestamps())
{
cop_req_context->add_resolved_locks(ts);
}

@ekexium ekexium Jul 17, 2026

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I mean here

client-c/src/kv/Scanner.cc

Lines 95 to 96 in 6b91f49

std::vector<uint64_t> pushed{};
auto ms_before_expired = snap.cluster->lock_resolver->resolveLocks(bo, snap.version, locks, pushed);

@windtalker windtalker Jul 17, 2026

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Good catch. Scanner missed this path. Fixed it by adding returned pushed into snap.min_commit_ts_pushed after resolving scan response locks, and by adding snap.min_commit_ts_pushed to ScanRequest.context.resolved_locks on retry. Also added a scanner regression test for the committed-after-read case.

}

bool exists = true;
if (clean_txns.find(lock->txn_id) == clean_txns.end())
{
Expand Down
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