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Insight into queries?

traveler_hauptmantraveler_hauptman Member, OS Professional, Mentor, Developers Posts: 419 PRO
I feel like I'm not getting the query system. I get the basics. But then I see something like this:
export function evLength(context is Context, arg is map) returns ValueWithUnits
<snip>
var edges = qEntityFilter(arg.entities, EntityType.EDGE);
var ownedEdges = qOwnedByBody(arg.entities, EntityType.EDGE);
return @evLength(context, { "edges" : qUnion([edges, ownedEdges]) }) * meter;

and I get confused.

Why did qEntityFilter not capture the edges owned by entities, making the qUnion necessary?

Does qEntityFilter only work on things that are not owned?


Comments

  • ilya_baranilya_baran Onshape Employees, Developers, HDM Posts: 952
    In this case, arg.entities queries for a mixture of edges and bodies.  qEntityFilter just extracts the edges that are directly queried for.  qOwnedByBody just looks at the bodies -- and then gets their owned edges.  Another way to thing about it is that the result of a qEntityFilter query is always a subset of the subquery passed in -- that's what it means to filter -- so it would be weird if you pass in one body into qEntityFilter and out comes a whole bunch of edges.

    I'm not sure if that makes it more or less clear...
    Ilya Baran \ Director, Architecture and FeatureScript \ Onshape Inc
  • traveler_hauptmantraveler_hauptman Member, OS Professional, Mentor, Developers Posts: 419 PRO
    edited April 2016
    That clears it up. It did not occur to me that bodies would be the query passed to qOwnedByBody. I thought it was taking a list of edges and returning edges that were owned by a body.


  • ilya_baranilya_baran Onshape Employees, Developers, HDM Posts: 952
    Ah, ok.  Actually, *every* edge (and face and vertex) is owned by some body.  You can get that body using qOwnerBody.
    Ilya Baran \ Director, Architecture and FeatureScript \ Onshape Inc
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