data_batcher

Description:

data batcher

Data Batcher #
Data batcher batches and de-dupes data fetched in the same cycle of the event loop.
final batcher = DataBatcher<String>(
execute: (ids) async {
print(ids) // ['1', '2', '3', '4']
return Api.fetch(ids);
},
);

batcher.add('1');
batcher.add('2');

batcher.addMany(['2', '3']);

await batcher.add('4');
copied to clipboard
When IDs are added to a batcher, they are grouped by the current cycle of the event loop and scheduled to be executed on a micro-task.
Once executed successfully, the batcher resolves each caller's future with its data as shown below:
final batcher = DataBatcher<String>(
execute: (ids) async {
return ['a', 'b', 'c'];
},
);

batcher.add('1').then(((resp) => print(resp)); // 'a'
batcher.add('2').then(((resp) => print(resp)); // 'b'

batcher.addMany(['2', '3']).then(((resp) => print(resp)) // ['b', 'c']
copied to clipboard
Data added to a batcher across different ticks of the event loop is broken into separate batches:
final batcher = DataBatcher<String>(
execute: (ids) async {
print(ids);
// ['1', '2']
// ['3']
return Api.fetch(ids);
},
);

batcher.add('1');
await batcher.add('2');

batcher.add('3');
copied to clipboard
By default, data IDs that are still in-flight from a previous batch which are requested again are not re-fetched:
final batcher = DataBatcher<String>(
execute: (ids) async {
print(ids);
// ['1', '2']
return Future.delayed(Duration(seconds: 5));
},
);

batcher.add('1');
batcher.add('2');

await Future.delayed(Duration(seconds: 1));

batcher.add('1');
copied to clipboard
The second attempt to request data with ID 1 is de-duped, since it is called while the in-flight request for '1' and '2' has not resolved. The Future returned by the second call to add ID 1 will resolve when the first original batch succeeds and with its returned value for ID 1.
If de-duping of in-flight data is not preferred, the dedupeInFlight flag can be set to false:
final batcher = DataBatcher<String>(
dedupeInFlight: false,
execute: (ids) async {
print(ids);
// ['1', '2']
// ['1']
return Future.delayed(Duration(seconds: 5), () {...});
},
);

batcher.add('1');
batcher.add('2');

await Future.delayed(Duration(seconds: 1));

batcher.add('1');
copied to clipboard
IDs are mapped to data responses using the order of the returned data. If needed, an idExtractor can be specified instead in order to associated response data with its matching input ID:
final batcher = DataBatcher<DataModel>(
idExtractor: (dataModel) => dataModel.id,
execute: (ids) async {
print(ids);
// ['1', '2']
return [DataModel('1'), DataModel('2')]
},
);

batcher.add('1');
batcher.add('2');
copied to clipboard