#140 Persist multiple events in batch

[fbrns]

#140 Persist multiple events in batch

Sketch for the Release notes:

• When you fire multiple similar events at once (in the same transaction), you can now use the plural fire*Events methods to store them all in one go into the database, instead of one-by-one. This increases throughput.
• If you used EventLogRepository.persist directly (you shouldn't!), it was previously storing the database ID of the new object back into the EventLog object. This is not happening anymore (in exchange for more efficiency for bulk inserts).

[ePaul]

Please also extend the README in the section Creating events.

[ePaul]

I guess I missed this on my first round (or these methods were not yet there?).
Is there a reason we pass a map here instead of just one data type and a collection of DTOs?
For all data event types I know, the data_type attribute is effectively constant (and/or ignored).

Do you have examples where regularly different values of data_type are sent on the same event type?
If not, I would go for the simpler signature:

Suggested change

	* @param dataTypeToData
	* the content of the {@code data_type} field of the Nakadi
	* event mapped to some POJOs that can be serialized into JSON (required
	* parameter). This is meant to be a representation of the
	* current state of the resource. It will be used as content of
	* the {@code data} field of the Nakadi event.
	*/
	@Transactional
	void fireCreateEvents(String eventType, Map<String, Collection<Object>> dataTypeToData);
	* @param dataType
	* the content of the {@code data_type} field of the Nakadi
	* event
	* @param data
	* some POJOs that can be serialized into JSON (required
	* parameter). This is meant to be a representation of the
	* current state of the resource. It will be used as content of
	* the {@code data} field of the Nakadi event.
	*/
	@Transactional
	void fireCreateEvents(String eventType, String dataType, Collection<Object> data);

(And analogously for the other methods.)

[ePaul]

Could you do the same change for the other fire methods, and also the example in the README?

[ePaul]

In this class the indentation was changed from 4 to 2. Could you please undo this? It makes seeing the actual change quite difficult.
Similarly, in some other files the indentation for new vs. old code doesn't match.

[ePaul]

Except from this, it looks good. 👍

[ePaul]

@fbrns I've just changed the type of data to Collection<?> from Collection<Object> (for all the plural fire methods).

This makes it easier to put e.g. a List<DomainObject> into it, without having to unpack and repack it first, or do an unsafe cast (and as we don't actually write anything into this collection here, it's not needed to have a concrete type).

(I actually wanted to create a PR to your branch, but accidentally pushed directly to your branch.)

[ePaul]

👍

[fbrns]

👍