Transactions | UStore for C++

API

transaction_tA transaction, which owns its handle and serves one call at a time.

class transaction_t

It never commits on destruction, never copies, and holds its database open until destroyed, so it may outlive its database_t.

read_stamp_tThe stamp a transaction or a snapshot reads at, which a commit validates against.

enum read_stamp_t

commit_stamp_tA commit's position in commit order, visible to every snapshot reading at or above it.

enum commit_stamp_t

Classtransaction_ref_tA transaction, as the calls on one executor see it, without owning either.9

class transaction_ref_t

Batched writes are buffered in the layout the engine prefers until the commit, so a transaction also saves preprocessing.

transaction_ref_t

transaction_ref_t() noexcept=default;

transaction_ref_t(receiver_t receiver) noexcept;

onThe same transaction, running every call on executor.

transaction_ref_t on(ustore_executor_t executor) const noexcept;

deferredThe same transaction, whose verbs submit to executor and answer deferred calls.

deferred_transaction_t deferred(
    ustore_executor_t executor) const noexcept;

containsWhether a collection named name exists at the head.

expected<bool> contains(std::string_view name) noexcept;

findOpens a view of one collection that follows this transaction.

template <typename collection_type_ = blobs_collection_t>
expected<collection_type_> find(std::string_view name) noexcept;

resetOpens the transaction, or clears it for reuse, keeping its memory and starting a new generation.

status_t reset() noexcept;

stageStages the transaction as the first phase of a two-phase commit, answering the stamp it reads at.

expected<read_stamp_t> stage() noexcept;

rollbackWithdraws a stage, releasing what it claimed while keeping the reads and writes, so the transaction can stage or commit again.

status_t rollback() noexcept;

commitCommits every update of the transaction, or none of them if any one fails, answering the commit's position in commit order.

expected<commit_stamp_t> commit(
    ustore_durability_t durability = ustore_durability_buffered_k) noexcept;

`durability`	in	Whether the call returns only after the data reaches the disk.