Hey!

Here's a few performance relevant changes I think should get merged before we branch next week:

https://gerrit.wikimedia.org/r/#/c/170961/ "Determine update actions based on usage aspects." <--- the last bit missing for usage tracking

https://gerrit.wikimedia.org/r/#/c/176650/ "Use wb_terms table for label lookup." <--- should improve memory consumption a lot, and possibly also speed.

https://gerrit.wikimedia.org/r/#/c/167224/ "Defer entity deserialization" <--- should reduce memory footprint and improve speed of trivial operations like checkign whether something is a redirect.

Are there any other performance improvements that we should get in? I imagine that this will be the last time we branch until the third week of January.