Transactions

ACID transactions ensure atomicity, consistency, isolation, and durability for multi key operations.

Begin a Transaction

var txn = try db.begin(false); // false = read-write
// or
var txn = try db.begin(true);  // true = read-only

Transaction Operations

// Read
const val = txn.get("key1");

// Write
try txn.put("key1", "value1");
try txn.put("key2", "value2");

// Delete
try txn.delete("key1");

Commit

Persist all changes atomically:

try db.commitTransaction(&txn);

Rollback

Discard all changes:

try db.rollbackTransaction(&txn);

view() - Auto Rollback Read

Read within a transaction that automatically rolls back:

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

NOTE

view() is read only and automatically rolls back when the closure returns — no manual cleanup needed.

update() - Auto Commit Write

Write within a transaction that automatically commits:

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

IMPORTANT

update() automatically commits all writes when the closure completes. If the closure returns early, changes are still committed.

Example: Bank Transfer

var txn = try db.begin(false);
try txn.put("account:alice:balance", "900");
try txn.put("account:bob:balance", "600");
try db.commitTransaction(&txn);

Example: Failed Transfer (Rollback)

var txn = try db.begin(false);
try txn.put("account:alice:balance", "0");
try db.rollbackTransaction(&txn);
// Alice's balance unchanged

CAUTION

Always call commitTransaction() or rollbackTransaction() to avoid leaving uncommitted transactions open.