tree a12e1f438342aa9ec1846089fc255bf2abb18ad3
parent fb64609c3f1d3492f4d80807f5d91894fa147172
author Nathan Harmata <nharmata@google.com> 1488232556 +0000
committer Yue Gan <yueg@google.com> 1488281588 +0000

Reimplement blaze query using an async evaluation model. Use a concurrent backend for SkyQueryEnvironment's implementation in order to achieve parallelism.

Advantages:
-New design has no flaws that the old design had.
-Code is structured so that deadlocks due to thread starvation are impossible (yup!).

Disadvantages:
-The meat of this change needs to all be in a single CL because every single QueryFunction and QueryExpression needs to be rewritten in the async style.

Still TODO:
-Fully embrace the async model in all QueryFunctions (e.g. 'rdeps', 'allpaths').
-Use concurrency in BlazeQueryEnvironment to achieve parallel evaluation for (non SkyQuery) 'blaze query' and genquery.

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PiperOrigin-RevId: 148690279
MOS_MIGRATED_REVID=148690279