public abstract class PrefixTreeStrategy extends SpatialStrategy
SpatialPrefixTree
. The two
subclasses are RecursivePrefixTreeStrategy
and TermQueryPrefixTreeStrategy
. This strategy is most effective as a fast
approximate spatial search filter.
Characteristics:
RecursivePrefixTreeStrategy
can effectively search non-point shapes.createIndexableFields(org.locationtech.spatial4j.shape.Shape)
for a document or by giving it some sort of Shape aggregate (e.g. JTS
WKT MultiPoint). The shape's boundary is approximated to a grid precision.
SpatialOperation.Intersects
is supported. If only points are indexed then this is effectively equivalent
to IsWithin.makeDistanceValueSource(org.locationtech.spatial4j.shape.Point,double)
even for multi-valued data, so long as the indexed data is all points; the
behavior is undefined otherwise. However, it will likely be removed in
the future in lieu of using another strategy with a more scalable
implementation. Use of this call is the only
circumstance in which a cache is used. The cache is simple but as such
it doesn't scale to large numbers of points nor is it real-time-search
friendly.Implementation:
The SpatialPrefixTree
does most of the work, for example returning
a list of terms representing grids of various sizes for a supplied shape.
An important
configuration item is setDistErrPct(double)
which balances
shape precision against scalability. See those javadocs.
Modifier and Type | Field and Description |
---|---|
protected int |
defaultFieldValuesArrayLen |
protected double |
distErrPct |
static FieldType |
FIELD_TYPE |
protected SpatialPrefixTree |
grid |
protected boolean |
pointsOnly |
ctx
Constructor and Description |
---|
PrefixTreeStrategy(SpatialPrefixTree grid,
String fieldName) |
Modifier and Type | Method and Description |
---|---|
HeatmapFacetCounter.Heatmap |
calcFacets(IndexReaderContext context,
Bits topAcceptDocs,
org.locationtech.spatial4j.shape.Shape inputShape,
int facetLevel,
int maxCells)
Computes spatial facets in two dimensions as a grid of numbers.
|
protected Iterator<Cell> |
createCellIteratorToIndex(org.locationtech.spatial4j.shape.Shape shape,
int detailLevel,
Iterator<Cell> reuse) |
Field[] |
createIndexableFields(org.locationtech.spatial4j.shape.Shape shape)
Returns the IndexableField(s) from the
shape that are to be
added to the Document . |
Field[] |
createIndexableFields(org.locationtech.spatial4j.shape.Shape shape,
double distErr)
Turns
SpatialPrefixTree.getTreeCellIterator(Shape, int) into a
TokenStream . |
Field[] |
createIndexableFields(org.locationtech.spatial4j.shape.Shape shape,
int detailLevel) |
double |
getDistErrPct() |
SpatialPrefixTree |
getGrid() |
protected boolean |
isPointShape(org.locationtech.spatial4j.shape.Shape shape)
Returns true if the
shape is a Point . |
boolean |
isPointsOnly() |
DoubleValuesSource |
makeDistanceValueSource(org.locationtech.spatial4j.shape.Point queryPoint,
double multiplier)
Make a ValueSource returning the distance between the center of the
indexed shape and
queryPoint . |
protected CellToBytesRefIterator |
newCellToBytesRefIterator() |
void |
setDefaultFieldValuesArrayLen(int defaultFieldValuesArrayLen)
A memory hint used by
SpatialStrategy.makeDistanceValueSource(org.locationtech.spatial4j.shape.Point)
for how big the initial size of each Document's array should be. |
void |
setDistErrPct(double distErrPct)
The default measure of shape precision affecting shapes at index and query
times.
|
void |
setPointsOnly(boolean pointsOnly)
True if only indexed points shall be supported.
|
getFieldName, getSpatialContext, makeDistanceValueSource, makeQuery, makeRecipDistanceValueSource, toString
protected final SpatialPrefixTree grid
protected int defaultFieldValuesArrayLen
protected double distErrPct
protected boolean pointsOnly
public static final FieldType FIELD_TYPE
public PrefixTreeStrategy(SpatialPrefixTree grid, String fieldName)
public SpatialPrefixTree getGrid()
public void setDefaultFieldValuesArrayLen(int defaultFieldValuesArrayLen)
SpatialStrategy.makeDistanceValueSource(org.locationtech.spatial4j.shape.Point)
for how big the initial size of each Document's array should be. The
default is 2. Set this to slightly more than the default expected number
of points per document.public double getDistErrPct()
public void setDistErrPct(double distErrPct)
SpatialPrefixTree.getMaxLevels()
);
this applies to all other shapes. Specific shapes at index and query time
can use something different than this default value. If you don't set a
default then the default is SpatialArgs.DEFAULT_DISTERRPCT
--
2.5%.SpatialArgs.getDistErrPct()
public boolean isPointsOnly()
public void setPointsOnly(boolean pointsOnly)
public Field[] createIndexableFields(org.locationtech.spatial4j.shape.Shape shape)
SpatialStrategy
shape
that are to be
added to the Document
. These fields
are expected to be marked as indexed and not stored.
Note: If you want to store the shape as a string for retrieval in search results, you could add it like this:
document.add(new StoredField(fieldName,ctx.toString(shape)));The particular string representation used doesn't matter to the Strategy since it doesn't use it.
createIndexableFields
in class SpatialStrategy
public Field[] createIndexableFields(org.locationtech.spatial4j.shape.Shape shape, double distErr)
SpatialPrefixTree.getTreeCellIterator(Shape, int)
into a
TokenStream
.public Field[] createIndexableFields(org.locationtech.spatial4j.shape.Shape shape, int detailLevel)
protected CellToBytesRefIterator newCellToBytesRefIterator()
protected Iterator<Cell> createCellIteratorToIndex(org.locationtech.spatial4j.shape.Shape shape, int detailLevel, Iterator<Cell> reuse)
public DoubleValuesSource makeDistanceValueSource(org.locationtech.spatial4j.shape.Point queryPoint, double multiplier)
SpatialStrategy
queryPoint
. If there are multiple indexed shapes
then the closest one is chosen. The result is multiplied by multiplier
, which
conveniently is used to get the desired units.makeDistanceValueSource
in class SpatialStrategy
public HeatmapFacetCounter.Heatmap calcFacets(IndexReaderContext context, Bits topAcceptDocs, org.locationtech.spatial4j.shape.Shape inputShape, int facetLevel, int maxCells) throws IOException
protected boolean isPointShape(org.locationtech.spatial4j.shape.Shape shape)
shape
is a Point
. For custom spatial contexts, it may make sense to
have certain other shapes return true.Copyright © 2000-2018 Apache Software Foundation. All Rights Reserved.