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fix: Add type safety to FindMutable calls #5886

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Merged
merged 2 commits into from
Oct 7, 2025
+29 −27
Merged

fix: Add type safety to FindMutable calls #5886

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913c6cd
fix: Add type safety to FindMutable calls
vyavdoshenko Oct 6, 2025
99945be
fix: review comments
vyavdoshenko Oct 7, 2025
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8 changes: 5 additions & 3 deletions src/server/hset_family.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1164,9 +1164,11 @@ void HSetFamily::HRandField(CmdArgList args, const CommandContext& cmd_cntx) {
}

if (string_map->Empty()) { // Can happen if we use a TTL on hash members.
// post_updater will run immediately
auto it = db_slice.FindMutable(db_context, key).it;
db_slice.Del(db_context, it);
auto res_it = db_slice.FindMutable(db_context, key, OBJ_HASH);
if (res_it) {
res_it->post_updater.Run();
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why do you need to run it manually?

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AutoUpdater dtor automatically calls Run() on destruction, which has a DCHECK that verifies the key still exists in the database.
Since we call db_slice.Del() earlier in the code (which removes the key), we must manually call post_updater.Run() before deletion to update memory accounting while the key is still valid. Otherwise, when res_it goes out of scope, the destructor will call Run() on an already-deleted key and the DCHECK will fail.
This pattern is used throughout the codebase whenever a key is deleted after FindMutable().

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maybe we can unify somehow this code, I mean do delete in post_updater or call run during delete.

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This pattern (post_updater.Run() + Del()) appears many times across several files in the codebase, so unifying it makes sense.

Suggested approach:
Add a new method DelMutable() to DbSlice:

void DbSlice::DelMutable(Context cntx, ItAndUpdater& it_updater) {
  it_updater.post_updater.Run();
  Del(cntx, it_updater.it);
}

This would simplify code like:

// From
res_it->post_updater.Run();
db_slice.Del(op_args.db_cntx, res_it->it);

// To
db_slice.DelMutable(op_args.db_cntx, *res_it);

However, I'd suggest doing this as a separate follow-up PR after this one, because:

  • This PR focuses on type safety fixes
  • Refactoring many call sites is a larger change that deserves separate review
  • Mixing two different goals increases risk and review complexity

Maybe better create a separate issue for this refactoring?

db_slice.Del(db_context, res_it->it);
}
return facade::OpStatus::KEY_NOTFOUND;
}
} else if (pv.Encoding() == kEncodingListPack) {
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7 changes: 4 additions & 3 deletions src/server/set_family.cc
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Expand Up @@ -481,9 +481,10 @@ OpResult<uint32_t> OpAdd(const OpArgs& op_args, std::string_view key, const NewE
// to overwrite the key. However, if the set is empty it means we should delete the
// key if it exists.
if (overwrite && (vals_it.begin() == vals_it.end())) {
auto it = db_slice.FindMutable(op_args.db_cntx, key).it; // post_updater will run immediately
if (IsValid(it)) {
db_slice.Del(op_args.db_cntx, it);
auto res_it = db_slice.FindMutable(op_args.db_cntx, key, OBJ_SET);
if (res_it) {
res_it->post_updater.Run();
db_slice.Del(op_args.db_cntx, res_it->it);
if (journal_update && op_args.shard->journal()) {
RecordJournal(op_args, "DEL"sv, ArgSlice{key});
}
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41 changes: 20 additions & 21 deletions src/server/string_family.cc
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Expand Up @@ -285,9 +285,12 @@ OpResult<int64_t> OpIncrBy(const OpArgs& op_args, string_view key, int64_t incr,
auto& db_slice = op_args.GetDbSlice();

// we avoid using AddOrFind because of skip_on_missing option for memcache.
auto res = db_slice.FindMutable(op_args.db_cntx, key);
auto res = db_slice.FindMutable(op_args.db_cntx, key, OBJ_STRING);

if (!res) {
if (res.status() == OpStatus::WRONG_TYPE)
return res.status();

if (!IsValid(res.it)) {
if (skip_on_missing)
return OpStatus::KEY_NOTFOUND;

Expand All @@ -300,11 +303,8 @@ OpResult<int64_t> OpIncrBy(const OpArgs& op_args, string_view key, int64_t incr,
return incr;
}

if (res.it->second.ObjType() != OBJ_STRING) {
return OpStatus::WRONG_TYPE;
}

auto opt_prev = res.it->second.TryGetInt();
// Type is already checked by FindMutable (OBJ_STRING)
auto opt_prev = res->it->second.TryGetInt();
if (!opt_prev) {
return OpStatus::INVALID_VALUE;
}
Expand All @@ -316,8 +316,8 @@ OpResult<int64_t> OpIncrBy(const OpArgs& op_args, string_view key, int64_t incr,
}

int64_t new_val = prev + incr;
DCHECK(!res.it->second.IsExternal());
res.it->second.SetInt(new_val);
DCHECK(!res->it->second.IsExternal());
res->it->second.SetInt(new_val);

return new_val;
}
Expand Down Expand Up @@ -383,20 +383,19 @@ OpResult<array<int64_t, 5>> OpThrottle(const OpArgs& op_args, const string_view
// Cost of this request
const int64_t increment_ns = emission_interval_ns * quantity; // should be nonnegative

auto res = db_slice.FindMutable(op_args.db_cntx, key);
auto res = db_slice.FindMutable(op_args.db_cntx, key, OBJ_STRING);
const int64_t now_ns = GetCurrentTimeNs();

int64_t tat_ns = now_ns;
if (IsValid(res.it)) {
if (res.it->second.ObjType() != OBJ_STRING) {
return OpStatus::WRONG_TYPE;
}

auto opt_prev = res.it->second.TryGetInt();
if (res) {
// Type is already checked by FindMutable (OBJ_STRING)
auto opt_prev = res->it->second.TryGetInt();
if (!opt_prev) {
return OpStatus::INVALID_VALUE;
}
tat_ns = *opt_prev;
} else if (res.status() == OpStatus::WRONG_TYPE) {
return res.status();
}

int64_t new_tat_ns = max(tat_ns, now_ns);
Expand Down Expand Up @@ -458,14 +457,14 @@ OpResult<array<int64_t, 5>> OpThrottle(const OpArgs& op_args, const string_view
// break behavior because the tat_ns value will be used to check for throttling.
const int64_t new_tat_ms =
(new_tat_ns + kMilliSecondToNanoSecond - 1) / kMilliSecondToNanoSecond;
if (IsValid(res.it)) {
if (IsValid(res.exp_it)) {
res.exp_it->second = db_slice.FromAbsoluteTime(new_tat_ms);
if (res) {
if (IsValid(res->exp_it)) {
res->exp_it->second = db_slice.FromAbsoluteTime(new_tat_ms);
} else {
db_slice.AddExpire(op_args.db_cntx.db_index, res.it, new_tat_ms);
db_slice.AddExpire(op_args.db_cntx.db_index, res->it, new_tat_ms);
}

res.it->second.SetInt(new_tat_ns);
res->it->second.SetInt(new_tat_ns);
} else {
CompactObj cobj;
cobj.SetInt(new_tat_ns);
Expand Down
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