In-Memory Indexing¶

The geomesa-memory module provides a in-memory cache of SimpleFeatures that supports indexing and filtering, using the CQEngine collection query engine. This is implemented by the GeoCQEngine class.

Index Configuration¶

When creating a GeoCQEngine, the attributes to index are passed in as a list of tuples in the form (name, type), where name corresponds to the attribute name, and type corresponds to the CQEngine index type:

Index Type	Attribute Types	Description
`default`	Any	Choose index type based on the attribute type being indexed
`navigable`	Date and numeric types	Supports equality, greater than and less than
`radix`	String	Supports string matching operations
`unique`	String, integer or long	Supports unique values. The presence of duplicate values will cause an exception
`hash`	String, integer or long	Supports equality
`geometry`	Geometries	Custom index for geometry types

If there is no appropriate index to use for a query, the whole data set will be searched.

Sample usage¶

import org.geotools.filter.text.ecql.ECQL
import org.locationtech.geomesa.memory.cqengine.GeoCQEngine
import org.locationtech.geomesa.memory.cqengine.utils.CQIndexType
import org.locationtech.geomesa.utils.geotools.SimpleFeatureTypes

// setup
val spec = "Who:String,*Where:Point:srid=4326"
val sft = SimpleFeatureTypes.createType("test", spec)

def buildFeature(sft: SimpleFeatureType, fid: Int): SimpleFeature = ???

// create a new cache
val cq = new GeoCQEngine(sft, Seq(("Who", CQIndexType.DEFAULT), ("Where", CQIndexType.GEOMETRY)))

// add a collection of features
cq.insert(Seq.tabulate(1000)(i => buildFeature(sft, i)))

// add a single feature
val feature = buildFeature(sft, 1001)
cq.insert(feature)

// remove a single feature
cq.remove(feature.getID)

// get an iterator with all features that match a filter
val filter = ECQL.toFilter("Who = 'foo' AND BBOX(Where, 0, 0, 180, 90)")
val reader = cq.query(filter)

// clear the cache
cq.clear()

You can also choose the geometry index type. By default a Bucket index is used that provides better performance in case of frequent inserts or updates. In the case of you need to search inside a immutable (or with few variation) collection of data you can use the QuadTree or the SRTtree index. To do that you must create the GeoCqEngine as in the following:

val cq1 = new GeoCQEngine(featureType, Seq(("Who", CQIndexType.DEFAULT), ("Where", CQIndexType.GEOMETRY)),geoIndexType = GeoIndexType.STRtree,geoIndexParam = Option.apply(new STRtreeIndexParam(/*nodeCapacity*/10)))
val cq2 = new GeoCQEngine(featureType, Seq(("Who", CQIndexType.DEFAULT), ("Where", CQIndexType.GEOMETRY)),geoIndexType = GeoIndexType.QuadTree)