O C T O B E R 1 3 - 1 6 , 2 0 1 6 • A U S T I N , T X

Lucene/Solr Spatial in 2015 David Smiley

Search Engineer/Consultant (Freelance)

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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”

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More Spatial Contributors!

Spatial4j Lucene Solr

David Smiley ✔️ ✔️ ✔️

Ryan McKinley ✔️

Justin Deoliveira ✔️

Mike McCandless ✔️

Nick Knize ✔️

Karl Wright ✔️

Ishan Chattopadhyaya ✔️

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Agenda

New Features / Capabilities New Approaches Improvements Pending

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Topic: New Features

Heatmaps / grid faceting — Lucene, Solr Surface-of-sphere shapes (Geo3d) — Lucene Accurate indexed geometries — Lucene, Solr GeoJSON read/write — Spatial4j

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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

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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

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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, ... ]] ...

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Solr Heatmap Resources

Solr Ref guide: https://cwiki.apache.org/confluence/display/solr/Spatial+Search Jack Reed’s Tutorial: http://www.jack-reed.com/2015/06/29/visualizing-10-million-geonames-with-leaflet-solr-heatmap-facets.html Live Demo: http://worldwidegeoweb.com Open-source JavaScript Solr Heatmap Libraries

https://github.com/spacemansteve/SolrHeatmapLayer https://github.com/mejackreed/leaflet-solr-heatmap https://github.com/voyagersearch/leaflet-solr-heatmap

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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

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All 2D Maps of the Earth Distort Straight Lines

A straight bird-flies path from Anchorage to Miami doesn’t actually cross the ocean!

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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

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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

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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

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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

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Topic: New Approaches

Lucene BKD Tree Indexes GeoPointField

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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/

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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

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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

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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

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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

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…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

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Topic: Improvements

Spatial4j Minimal longitude bounding-box algorithm

Lucene (PrefixTree / RPT indexing) Leaner & faster non-point indexes New PackedQuadPrefixTree

Solr Distance units: Kilometers/Miles/Degrees Nicer ST_* spatial query parsers (almost done)

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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. :-)

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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