3. 3
About David Smiley
Freelance Search Developer/Consultant
Expert Lucene/Solr development skills,
advise (consulting), training
Java, spatial, and full-stack experience
Apache Lucene/Solr committer & PMC member
Primary author of “Apache Solr Enterprise Search Server”
4. 4
More Spatial Contributors!
Spatial4j Lucene Solr
David Smiley ✔️ ✔️ ✔️
Ryan McKinley ✔️
Justin Deoliveira ✔️
Mike McCandless ✔️
Nick Knize ✔️
Karl Wright ✔️
Ishan Chattopadhyaya ✔️
6. 6
Topic: New Features
Heatmaps / grid faceting — Lucene, Solr
Surface-of-sphere shapes (Geo3d) — Lucene
Accurate indexed geometries — Lucene, Solr
GeoJSON read/write — Spatial4j
7. 7
Heatmaps: Spatial Grid Faceting
Spatial density summary grid faceting,
also useful for point-plotting search results
Usually rendered with a gradient radius
Lucene & Solr APIs
Scalable & fast usually…
v5.2
8. 8
Heatmaps Under the Hood
Requires a PrefixTreeStrategy Lucene field — grid based
Algorithm enumerates the underlying cell/terms and
accumulates the counter in a corresponding grid
Conceptually facet.method=enum for spatial
Works on non-point indexed shapes too
Complexity: O(cells * cellDepthFactor) not O(docs)
No/low memory; mainly the grid of integers
Solr will distribute to shards and merge
Could be faster still; a BFS (vs DFS) layout would be perfect
9. 9
Solr Heatmap Faceting
On an RPT field
(SpatialRecursivePrefixTreeFieldType)
prefixTree=“packedQuad”
Query:
/select?facet=true
&facet.heatmap=geo_rpt
&facet.heatmap.geom=
["-180 -90" TO "180 90”]
facet.heatmap.format=ints2D or png
// Normal Solr response...
"facet_counts":{
... // facet response fields
"facet_heatmaps":{
"loc_srpt":[
"gridLevel",2,
"columns",32,
"rows",32,
"minX",-180.0,
"maxX",180.0,
"minY",-90.0,
"maxY",90.0,
"counts_ints2D", [null, null, [0, 0, ... ]]
...
11. 11
Geo3D: Shapes on the Surface of a Sphere
… or Ellipsoid of configurable axis
Not a general 3D space geometry lib
Internally uses geocentric X, Y, Z coordinates (hence 3D) with
3D planar geometry mathematics
Shapes: Point, Lat-Lon Rect, Circle, Polygons, Path (LineString)
with optional buffer
Distance computations: Arc (angular or surface), Linear
(straight-line), Normal
12. 12
All 2D Maps of the Earth Distort Straight Lines
A straight bird-
flies path from
Anchorage to
Miami doesn’t
actually cross the
ocean!
13. 13
Geo3D, continued…
Benefits
Inherently more accurate than 2D projected spatial
especially for big shapes or near poles
Many computations are fast; no expensive trigonometry
An alternative to JTS without the LGPL license (still)
Has own Lucene module (spatial3d), thus jar file
Maven groupId: org.apache.lucene, artifact: lucene-spatial3d
No Solr integration yet; pending more Spatial4j integration
14. 14
Index & Search Geo3D Geometries
Spatial4j Geo3dShape
wrapper with RPT
In Lucene-spatial for now
Index Geo3d shapes
Limited to grid accuracy
Query by Geo3d shape
Limited distance sort
Heatmaps
Geo3DPointField &
PointInGeo3DShapeQuery
Based on a 3D BKD index
In spatial3d module
Index points-only
No multi-valued
Query by Geo3d shape
No distance sort
Leaner & faster than RPT
v5.4v5.2
15. 15
RPT/SpatialPrefixTrees and Accuracy
RecursivePrefixTree (RPT) uses Lucene’s index as a PrefixTree
Thus represents shapes as grid cells of varying precision by
prefix
Example, a point shape:
D, DR, DRT, DRT2, DRT2Y
More accuracy scales
Example, a polygon shape:
Too many to list… 508 cells
More accuracy does NOT scale
16. 16
Combining RPT with Serialized Geometry
RPT (RecursivePrefixTreeStrategy) is the grid index (inaccurate)
SDV (SerializedDVStrategy) stores serialized geometry (accurate)
RPT + SDV → CompositeSpatialStrategy
Accuracy & speed & smaller indexes
Optimized intersects predicate avoids some geometry checks
> 80% faster intersects queries, 75% smaller index
Solr adapter: RptWithGeometrySpatialField
Compatible with the Heatmaps feature
Includes a shape cache (per-segment); configurable
v5.2
18. 18
BKD Tree Indexes
New numeric/spatial index approach with own file format
Not based on Lucene Terms index
https://www.cs.duke.edu/~pankaj/publications/papers/bkd-sstd.pdf
Much faster and compact than Trie/PrefixTree based indexes
Wither term auto-prefixing? LUCENE-5879
Indexed point-data only; multi-valued mostly
Intersects predicate only
Filtering only (no distance or other scoring)
Multiple implementations… (next slide)
Neat visualization https://youtu.be/
19. 19
Multiple BKD Implementations
Multiple implementations of the same BKD concept:
(1D) RangeTreeDocValuesFormat
(2D) BKDPointField & BKD…Query
(3D) Geo3DPointField & PointInGeo3DShapeQuery
(ND) LUCENE-6825 (to Lucene-core) in-progress
1D,2D,3D Implementations are either in lucene-sandbox or
lucene-spatial3d for now
No Lucene-spatial module SpatialStrategy wrappers yet
thus no Spatial4j Shape integration nor Solr integration yet
20. 20
BKD 1D: RangeTree
Efficient range search on single/multi-valued numbers or terms
Could be used for numbers, dates, IPV6 bytes, …
Alternatives: Normal number fields (trie), DateRangeField (RPT)
Would love to see a benchmark!
How-To:
RangeTreeDocValuesFormat
Numbers: SortedNumericDocValuesField with
NumericRangeTreeQuery
Bytes: SortedSetDocValuesField with SortedSetRangeTreeQuery
v5.3
21. 21
BKD 2D: BKDPointField
Efficient 2D geospatial point index
Alternative to RPT or GeoPointField
5.7x faster than RPT w/ GeoHash. Smaller indexes.
How-To:
Use BKDPointField (requires BKDTreeDocValuesFormat)
Query:
BKDPointInBBoxQuery
BKDPointInPolygonQuery
point-radius (circle) — in-progress LUCENE-6698
v5.3
22. 22
GeoPointField
2D geospatial point field
Indexed point-only data, single/multi-valued
Spatial 2D Trie/PrefixTree terms index
But not affiliated with Lucene-spatial SpatialPrefixTree/RPT
Configurable 2x
grid size (defaults to 512)
Compact bit interleaved Z-order encoding
Re-uses much of Lucene’s numeric precisionStep &
MultiTermQuery logic
2-phase grid/postings then doc-values algorithm
v5.3
23. 23
…continued
Has no affiliation with Spatial4j, RPT, JTS, or SpatialStrategy
No Heatmaps, No custom Shape implementations
No Solr support yet
No dependencies
Easy to use compared to RPT; simpler internally too
How-To:
doc.add(new GeoPointField(name, lon, lat, Store.YES))
GeoPointDistanceQuery (sphere only) or GeoPointInBBoxQuery
or GeoPointInPolygonQuery. …DistanceRangeQuery pending
25. 25
Topic: Some Pending Spatial TODOs
Spatial4j
Geo3D integration — a JTS
alternative
Lucene
FlexPrefixTree — LUCENE-4922
Multi-dimensional BKD —
LUCENE-6825
SpatialStrategy adapters for
GeoPointField, etc.
Solr
Better spatial Solr
QParsers — SOLR-4242
GeoJSON parsing
More FieldType adapters
for latest Lucene spatial
DateRangeField faceting
Nearest-neighbor search
Well, 2015 isn’t over yet. :-)
26. 26
That’s all for now; thanks for coming!
Need Lucene/Solr guidance or custom development?
Contact me!
Email: dsmiley@apache.org
LinkedIn: http://www.linkedin.com/in/davidwsmiley
G+: +DavidSmiley
Twitter: @DavidWSmiley