BIND for Constants and variable renaming.

[joka921]

Implemented BIND( as ?variable) and BIND(?variable as ?otherVariable).

• There also is a stub for BIND( + ?else as ?sum), but that is not yet fully integrated ye

[hannahbast]

I just stumbled upon the following bug. The following query crashes any backend. It does not matter what the triple is. What matters is the combination of an aggregation over a non-existing variable and a BIND, though I don't understand why that matters):

SELECT ?x WHERE {
  { SELECT ?x (COUNT(?z) AS ?count) WHERE { ?x <bla> <blu> } GROUP BY ?x }
  BIND(?x AS ?whatever)
}

The last line in the log before the crash is:

Wed Apr 29 18:11:22.766	- DEBUG: Sort result computation...

[floriankramer]

It's been a while since I worked with QLever, so I might have missed some things, but overall this looks good to me. Unit tests and a toString for the bind grapg pattern are still missing though.

[hannahbast]

Pass in a 1-1 code review of Hannah and Johannes. Reviewed everything in detail, except the (non-trivial) changes in QueryPlanner.cpp

[joka921]

don't know how to cancel reviews...

[hannahbast]

Also reviewed the missing QueryPlanner.cpp in a 1-1 with Johannes.

[hannahbast]

Looks great, thank you very much. I guess the small code duplication for the pattern trick check (QueryPlanner.cpp lines 561-568 and lines 624-631) has historical reasons and can be fixed when QueryPlanner::optimize gets a major overhaul.