The Quest for Performance: smart Rete layouts

[bergmanngabor]

Implement various ideas for building a more clever Rete structure:

• ASAP trimming of variables not used later
• Clever node reuse
  • Find if a stub join also happens to join alternate stubs with the same underlying Rete node, and then consider the "free accidental" stub in further joins.
• Suggested order of join preference:
  • trivial joins (stub a = stub b)
  • high selectivity filters
  • supressed by joincandidate if already checked on other side
  • apply first to narrower stubs
  • aggregator quasijoins, let-expressions (?)
  • true joins
  • except cartesians
  • TBD: ranking based on what constraints the join will enable
  • low-selectivity filters (injectivity)
  • cartesian joins

[bergmanngabor]

Added the task of clever node reuse after the discussions at the latest meeting. Potential source of good test case: the thesis about GPU vs. EIQ performance supervised by @abelhegedus.

[bergmanngabor]

Migrated to https://bugs.eclipse.org/bugs/show_bug.cgi?id=398763