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Revert to use CachePrevValueIfNeeded(), but let it call GetString() if needed. (#1080)

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I believe this is a better API as it's harder to mistakenly use.

Signed-off-by: chakaz <chakaz@chakaz>
Co-authored-by: ashotland <ari@dragonflydb.io>
This commit is contained in:
Chaka 2023-04-12 22:19:06 +03:00 • committed by GitHub
parent 5fb5f54885
commit f013699613
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1 changed files with 8 additions and 13 deletions
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21
src/server/string_family.cc
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@ -482,14 +482,11 @@ class SetResultBuilder {
explicit SetResultBuilder(bool return_prev_value) : return_prev_value_(return_prev_value) {
}
// Calling GetString() copies `it`'s value, which is unnecessary in most case
bool ShouldReturnPrevValue() const {
return return_prev_value_;
}
void CachePrevValue(string_view value) {
DCHECK(return_prev_value_);
prev_value_ = value;
void CachePrevValueIfNeeded(EngineShard* shard, const PrimeValue& pv) {
if (return_prev_value_) {
// We call lazily call GetString() here to save string copying when not needed.
prev_value_ = GetString(shard, pv);
}
}
// Returns either the previous value or `status`, depending on return_prev_value_.
@ -521,8 +518,8 @@ OpResult<optional<string>> SetCmd::Set(const SetParams& params, string_view key,
if (params.IsConditionalSet()) {
const auto [it, expire_it] = db_slice.FindExt(op_args_.db_cntx, key);
if (result_builder.ShouldReturnPrevValue() && IsValid(it)) {
result_builder.CachePrevValue(GetString(shard, it->second));
if (IsValid(it)) {
result_builder.CachePrevValueIfNeeded(shard, it->second);
}
// Make sure that we have this key, and only add it if it does exists
@ -550,9 +547,7 @@ OpResult<optional<string>> SetCmd::Set(const SetParams& params, string_view key,
PrimeIterator it = get<0>(add_res);
if (!get<2>(add_res)) { // Existing.
if (result_builder.ShouldReturnPrevValue()) {
result_builder.CachePrevValue(GetString(shard, it->second));
}
result_builder.CachePrevValueIfNeeded(shard, it->second);
return std::move(result_builder).Return(SetExisting(params, it, get<1>(add_res), key, value));
}