Run batches in multisite within context of site that created them

[koen12344]

Fixes #126 and #127

[ianmjones]

Thanks for this @koen12344.

We'll have to give this a test and decide whether it's the way we'd like to tackle the problem, and consider whether it'll affect any current users.

In the meantime, I spotted a couple of potential issues that I thought I'd best bring to your attention in the code comments.

[ianmjones]

I think you probably need '_%' rather than '%' at the end here, otherwise you may be selecting for all subsites whose ID begins with the required ID, and any batch without a subsite ID that happens to have a generated key that begins with the subsite ID.

e.g. for subsite ID = 1, the following are going to match:

wibble_batch_1_1abcde <-- GOOD
wibble_batch_10_1abcde <-- BAD
wibble_batch_11_1abcde <-- BAD
wibble_batch_101_1abcde <-- BAD
wibble_batch_1abcde <-- BAD

[koen12344]

Good catch, I think you might be right about that.

[ianmjones]

I think you probably meant for this change to apply to the value passed into the inner apply_filters?

[w3guy]

I don't think this PR is necessary. We do this in our code to be multisite compatible

$this->prefix = 'wp_' . get_current_blog_id();