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add LocationIndexTree.query(BBox)#1485

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Merged
michaz merged 18 commits intomasterfromloc_index
Apr 17, 2019
Merged

add LocationIndexTree.query(BBox)#1485

michaz merged 18 commits intomasterfromloc_index
Apr 17, 2019

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@karussell
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@karussellkarussell commentedOct 16, 2018
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This PR adds a new query(BBox) method. Currently we can fetch only nodes from one leaf and so with this querying areas is inefficient. Related to#1127 and#1324.

Furthermore a possibility to visualize the index

image

and some description for the index is added. The description now makes clear that we have a Quadtree implementation with some special tuning. E.g. for bigger areas one node branches not only into 4 subtrees but can branch into 16. Previously also 64 was possible, but we removed this as this has no advantages in terms of storage, query or creation speed. (Measured it for Germany and world wide)

TODOs:

@karussellkarussell added this to the0.12 milestoneOct 16, 2018
if (bbox.contains(lat,lon))
indexNodeList.add(nodeId);

// TODO should be done behind the scene?
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Will make it possible via aSimpleVisitor class or something. Often this iteration has to be done again on the client side e.g. to fetch the edges and so this work would be an unnecessary overhead then.

@karussellkarussell modified the milestones:0.12,0.13Feb 25, 2019
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Nice, this closes some open ends for me. Is the current state mergeable, meaning, do we think that the bounding-box query does more or less what it should? Because I'd like to.

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Well, this is not fully ready unfortunately. Currently all nodes are returned where the tile intersects with the shape. This is ok for visualisation, but for other use cases we have to filter these nodes and call "shape.contains(node)" as a post processing step. Now the problem is that this could be done cheap like this or in a more expensive manner if we need high precision via "shape.intersects(edge.fetchWayGeometry)". Currently exploring the options on how to do this so that this also works for a Polygon (which basically means using JTS Polygon behind our Polygon class). But we could also bring it into a mergable state faster and I'll create a new issue for the open tasks.

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michaz commentedApr 12, 2019
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Oh, that's exactly what I need: "May include more nodes than are contained, but never fails to return return a node thatis contained". I think that's also how other implementations work.

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Oh, that's exactly what I need: "May include more nodes than are contained, but never fails to return return a node that is contained". I think that's also how other implementations work.

Ah, ok. I think there are indeed two use cases. This one, which you need and we need for fast visualization. But also the other to e.g. block certain edges but not too many!

Maybe I'll bring this PR in a mergable form for the first use case and explicitly mention this and work later on the second "high precision" use case?

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michaz commentedApr 12, 2019
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Maybe I'll bring this PR in a mergable form for the first use case and explicitly mention this and work later on the second "high precision" use case?

Yes, please! For me, this doesn't even mean that this is currently unfinished --filtering the result to the desired level of exclusivity is asecond task, and can happen outside of the current method. This one is finished.

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And this method can still narrow down what it returns later on without changing its promise.

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filtering the result to the desired level of exclusivity is a second task

This is exactly where I'm unsure because the methodindex.query(shape) could also imply that this should be an exact filter and no post-processing work needs to be done.

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Well, "query" as a method name is vague enough that I think it can't be misunderstood as promising anything specific. ;-)

Let's add a Javadoc which explains what this method does and does not (nothow it does that), and it'll be fine.

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Ok :D

Will do this ... let me just do some minor stuff.

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karussell commentedApr 12, 2019
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I did the following changes (let me know if this was too much):

  • moved the Visitor interfaces and the query method to the LocationIndex interface
  • removed the extra visualize method and made it possible via the Visitor setting isTileInfo (now Visitor has to be an abtract class as default methods are not possible in 7). onTile now directly includes the depth not the too-visualization-specificwidth.
  • avoid duplicate nodes (and edges for the EdgeVisitor)
  • introduced a new "queryBBox.contains" branch to avoid bbox checks on greater depths, should make the query slightly faster
  • renamed Shape.intersect to intersects, also to make later migrations to JTS easier
  • renamed*cell* to*tile*
  • made some methods non-public

@karussellkarussell requested a review frommichazApril 12, 2019 14:29
/**
* This interface allows to visit every node stored in the leafs of a LocationIndex.
*/
abstractclassVisitor {
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@michazmichazApr 14, 2019
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Just as a small remark: This Visitor is not very Java-8-friendly (see my call of the new query method in the commit I added - I can't do a lambda there, because the visitor is not a single-method interface but a multi-method abstract class), and also a bit unusual. If I understand it correctly, as a client, I have to overrideisTileInfo if I wantonTile to be called? I think interfaces are most clear when control flows in one direction only: An interface is either for me to call, or for me to implement and be called.

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An interface is either for me to call, or for me to implement and be called.

Okay, that's actually the case here. :-) But theinformation flows both ways.

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Yes, I tried with a separate QueryOptions class but this was not much prettier. Should I revert it back to this to make it easier with lambda?

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Ah no, it's okay.

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Thanks! I'm doing more Isochrone experiments with this right now... ,-)

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@michazmichaz merged commitfa78298 intomasterApr 17, 2019
@michazmichaz deleted the loc_index branchApril 22, 2020 20:31
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