Improvement/merged stream iterator

[basz]

implementation of prooph/pdo-event-store#201

some notes;

• works like any other iterator (no array result from current with results from multiple iterators)
• can work with any number of streams (but not zero)
• can query for streamName of current message (needed for tracking of projection positions)
• invalid iterators may become valid again while still iterating other valid ones without problem
• think it should be still fastish

[coveralls]

Coverage increased (+0.02%) to 99.031% when pulling f732532 on basz:improvement/merged-stream-iterator into a98615b on prooph:7.x.

[basz]

think this does the trick. eager to hear what you think. bas.

[basz]

heads up. I identified a bug.

[basz]

@prolic is there a reason you return false instead of null as defined by the interface?

https://github.com/prooph/pdo-event-store/blob/master/src/PdoStreamIterator.php#L188
https://php.net/manual/en/iterator.key.php

I would want to define public function key(): ?int within the MergedStreamIterator and simply return the contained (pdo) iterators key() result.

[prolic]

I don't think the return value of key() is used anywhere, or is it?

[basz]

I don't think the return value of key() is used anywhere, or is it?

No it isn’t (i think)