about lock

[Eag Dra]

Does Dexie have a lock mechanism and concepts? Or related API?

[David Fahlander]

Dexie and IndexedDB by itself has the concept of transactions which means that if you do an operation within a transaction, these operations will be atomic. 

Dexie also have an internal locking mechanism used when simulating sub-transactions that make sure a writeable sub transaction will lock the main transaction such that operations put on the main transaction will be queued until the sub transaction completes.

To accomplish locking, use a transaction:

function addFriendWithPet() {

  return db.transaction('rw', db.friends, db.pets, function () {

    db.friends.add({name: 'Foo'}).then(function (fooId) {

      return db.pets.add({name: 'FoosPet', friendId: fooId});

    });

  });

}

This will guarantee that the friend and its pet is added atomically.

In case this function is called from an already ongoing transaction, Dexie will simulate a sub transaction by locking the main transaction until the sub transaction is done. Example:

db.transaction('rw', db.friends, db.pets, function () {

   addFriendWithPet();

   db.pets.toArray().then(function (pets) {

     console.log(JSON.stringify(pets)); // Will contain the added pet even though we didnt wait for addFriendWithPet() to complete.

   });

});

Don't know if this was the answer to the question or not?