Transaction API

The Transaction struct provides ACID transactions for the database.

Creating a Transaction

// Write transaction
var txn = try db.transaction();

// Read only transaction
var txn = try db.readTransaction();
defer txn.deinit();

Transaction Operations

// Put
try txn.put("key", "value");

// Get
if (txn.get("key")) |val| {
    // use val
}

// Delete
try txn.delete("key");

Committing and Rolling Back

// Commit
try db.commitTransaction(&txn);

// Rollback
try db.rollbackTransaction(&txn);

Convenience Methods

view() — Auto Rollback Read

const result = try db.view(null, ?[]const u8, &(struct {
    fn f(_: void, txn: *zkv.mvcc.Transaction) ?[]const u8 {
        return txn.get("account:alice:balance");
    }
}.f));

update() — Auto Commit Write

try db.update(null, void, &(struct {
    fn f(_: void, txn: *zkv.mvcc.Transaction) void {
        txn.put("account:alice:balance", "1100") catch return;
        txn.put("account:bob:balance", "700") catch return;
    }
}.f));

TIP

Prefer view() and update() over manual transaction management. They handle commit and rollback automatically.

Properties

Property	Type	Description
read_only	bool	Whether transaction is read only
is_active	bool	Whether transaction is still active
write_set	ArrayList(Entry)	Pending writes
read_set	ArrayList([]const u8)	Keys read in this transaction

Error Handling

Transactions return errors for:

CAUTION

Writing in a read only transaction will return an error. Always use write transactions for mutations.

• Writing in a read only transaction
• Operating on an inactive (committed/rolled back) transaction
• Memory allocation failures