Transactions | UStore for Mojo

API

StructStampA position in the order commits apply in, ustore_stamp_t: where a commit landed, or the newest commit a transaction or a snapshot reads.1

struct Stamp

Fields

`value`	`UInt64`	The position, growing with every commit.

Values

`Written`	`Stamp`

Conforms to

Answer, Copyable, Defaultable, Deinitable, Equatable, ImplicitlyCopyable, Movable

__init__Stamp zero, which a failed call leaves.

def __init__(out self)

def __init__(out self, arena: Int, generation: Int, written: Self, count: Int)

Adopts the stamp a call wrote.

StructWatchWhether a transaction records the keys a call touches for conflicts, ustore_watch_t.

struct Watch

Fields

`code`	`c_int`	The raw `ustore_watch_t` value the ABI exchanges.

Values

`KEYS`	`Watch(Int32(0))`	Records the keys, so a concurrent change to any of them fails the commit.
`NONE`	`Watch(Int32(1))`	Records nothing.

Conforms to

Copyable, Deinitable, Equatable, ImplicitlyCopyable, Movable, RegisterPassable, TrivialRegisterPassable

StructIsolationHow the transactions of the in-memory engine see each other's writes, ustore_isolation_t.

struct Isolation

Fields

`code`	`c_int`	The raw `ustore_isolation_t` value the ABI exchanges.

Values

`STRICT_SERIALIZABLE`	`Isolation(Int32(0))`	Every transaction appears to run alone at one moment.
`SNAPSHOT`	`Isolation(Int32(1))`	Every transaction reads the state its start saw and conflicts only over what it writes.

Conforms to

Copyable, Deinitable, Equatable, ImplicitlyCopyable, Movable, RegisterPassable, TrivialRegisterPassable

StructTransactionAn optimistic transaction grouping operations across collections and modalities, freed when it goes out of scope. It holds its database open, and serves one call at a time.5

struct Transaction

Verbs called on it run on the calling thread, read through it and write into it, recording the keys they touch; txn.unwatched() records nothing, and txn.on(executor) and txn.deferred(executor) route the same verbs to an executor.

Fields

`library`	`Library`	The loaded engine.
`database`	`Address`	The `ustore_database_t` it belongs to.
`address`	`Address`	The opaque `ustore_transaction_t`.

Conforms to

BlobsVerbs, DatabaseVerbs, Deinitable, DocsVerbs, GraphVerbs, Movable, PagesVerbs, StringsVerbs

__init__Adopts a transaction the engine just began.

def __init__(out self, *, library: Library, database: Int, address: Int)

__deinit__Resets and frees the transaction. Calls ustore_transaction_free.

def __deinit__(deinit self)

unwatchedThe same verbs on the calling thread, recording nothing for conflicts. Binding-only.

def unwatched(ref self) -> On[origin_of(self)]

onThe same verbs, blocking on executor. Binding-only.

def on(ref self, ref executor: Executor, watch: Watch = Watch.KEYS) -> On[origin_of(executor, self)]

deferredThe same verbs, each submitted to executor and answering a Deferred at once. Binding-only.

def deferred(
    ref self,
    ref executor: Executor,
    watch: Watch = Watch.KEYS
) -> DeferredOn[origin_of(executor, self)]