org.apache.lucene.facet.search
Class FacetRequest

java.lang.Object
  org.apache.lucene.facet.search.FacetRequest

Direct Known Subclasses:

AssociationFloatSumFacetRequest, AssociationIntSumFacetRequest, CountFacetRequest, SumScoreFacetRequest

public abstract class FacetRequest
extends Object

Request to accumulate facet information for a specified facet and possibly also some of its descendants, upto a specified depth.

The facet request additionally defines what information should be computed within the facet results, if and how should results be ordered, etc.

An example facet request is to look at all sub-categories of "Author", and return the 10 with the highest counts (sorted by decreasing count).

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

static class	FacetRequest.FacetArraysSource Specifies which array of FacetArrays should be used to resolve values.
static class	FacetRequest.ResultMode Result structure manner of applying request's limits such as getNumLabel() and numResults.
static class	FacetRequest.SortOrder Requested sort order for the results.

Field Summary

CategoryPath	categoryPath
static int	DEFAULT_DEPTH Default depth for facets accumulation.
static FacetRequest.ResultMode	DEFAULT_RESULT_MODE Default result mode
int	numResults

Constructor Summary

FacetRequest(CategoryPath path, int numResults)
Initialize the request with a given path, and a requested number of facets results.

Method Summary

Aggregator	createAggregator(boolean useComplements, FacetArrays arrays, TaxonomyReader taxonomy) Create an aggregator for this facet request.
boolean	equals(Object o)
int	getDepth() How deeply to look under the given category.
abstract FacetRequest.FacetArraysSource	getFacetArraysSource() Returns the FacetRequest.FacetArraysSource this FacetRequest uses in getValueOf(FacetArrays, int).
int	getNumLabel() If getNumLabel() < getNumResults(), only the first getNumLabel() results will have their category paths calculated, and the rest will only be available as ordinals (category numbers) and will have null paths.
FacetRequest.ResultMode	getResultMode() Return the requested result mode.
FacetRequest.SortOrder	getSortOrder() Return the requested order of results.
abstract double	getValueOf(FacetArrays arrays, int idx) Return the value of a category used for facets computations for this request.
int	hashCode()
void	setDepth(int depth)
void	setNumLabel(int numLabel)
void	setResultMode(FacetRequest.ResultMode resultMode)
void	setSortOrder(FacetRequest.SortOrder sortOrder)
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_DEPTH

public static final int DEFAULT_DEPTH

Default depth for facets accumulation.

See Also:

getDepth(), Constant Field Values

DEFAULT_RESULT_MODE

public static final FacetRequest.ResultMode DEFAULT_RESULT_MODE

Default result mode

See Also:

getResultMode()

categoryPath

public final CategoryPath categoryPath

numResults

public final int numResults

Constructor Detail

FacetRequest

public FacetRequest(CategoryPath path,
                    int numResults)

Initialize the request with a given path, and a requested number of facets results. By default, all returned results would be labeled - to alter this default see setNumLabel(int).

NOTE: if numResults is given as Integer.MAX_VALUE than all the facet results would be returned, without any limit.

NOTE: it is assumed that the given CategoryPath is not modified after construction of this object. Otherwise, some things may not function properly, e.g. hashCode().

Throws:

IllegalArgumentException - if numResults is ≤ 0

Method Detail

createAggregator

public Aggregator createAggregator(boolean useComplements,
                                   FacetArrays arrays,
                                   TaxonomyReader taxonomy)
                            throws IOException

Create an aggregator for this facet request. Aggregator action depends on request definition. For a count request, it will usually increment the count for that facet.

Parameters:

useComplements - whether the complements optimization is being used for current computation.

arrays - provider for facet arrays in use for current computation.

taxonomy - reader of taxonomy in effect.

Throws:

IOException - If there is a low-level I/O error.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

getDepth

public final int getDepth()

How deeply to look under the given category. If the depth is 0, only the category itself is counted. If the depth is 1, its immediate children are also counted, and so on. If the depth is Integer.MAX_VALUE, all the category's descendants are counted.

getFacetArraysSource

public abstract FacetRequest.FacetArraysSource getFacetArraysSource()

Returns the FacetRequest.FacetArraysSource this FacetRequest uses in getValueOf(FacetArrays, int).

getNumLabel

public final int getNumLabel()

If getNumLabel() < getNumResults(), only the first getNumLabel() results will have their category paths calculated, and the rest will only be available as ordinals (category numbers) and will have null paths.

If Integer.MAX_VALUE is specified, all results are labled.

The purpose of this parameter is to avoid having to run the whole faceted search again when the user asks for more values for the facet; The application can ask (getNumResults()) for more values than it needs to show, but keep getNumLabel() only the number it wants to immediately show. The slow-down caused by finding more values is negligible, because the slowest part - finding the categories' paths, is avoided.

Depending on the LimitsMode, this limit is applied globally or per results node. In the global mode, if this limit is 3, only 3 top results would be labeled. In the per-node mode, if this limit is 3, 3 top children of the target category would be labeled, as well as 3 top children of each of them, and so forth, until the depth defined by getDepth().

See Also:

getResultMode()

getResultMode

public final FacetRequest.ResultMode getResultMode()

Return the requested result mode.

getSortOrder

public final FacetRequest.SortOrder getSortOrder()

Return the requested order of results.

getValueOf

public abstract double getValueOf(FacetArrays arrays,
                                  int idx)

Return the value of a category used for facets computations for this request. For a count request this would be the count for that facet, i.e. an integer number. but for other requests this can be the result of a more complex operation, and the result can be any double precision number. Having this method with a general name value which is double precision allows to have more compact API and code for handling counts and perhaps other requests (such as for associations) very similarly, and by the same code and API, avoiding code duplication.

Parameters:

arrays - provider for facet arrays in use for current computation.

idx - an index into the count arrays now in effect in arrays. E.g., for ordinal number n, with partition, of size partitionSize, now covering n, getValueOf would be invoked with idx being n % partitionSize.

hashCode

public int hashCode()

Overrides:

hashCode in class Object

setDepth

public void setDepth(int depth)

setNumLabel

public void setNumLabel(int numLabel)

setResultMode

public void setResultMode(FacetRequest.ResultMode resultMode)

Parameters:

resultMode - the resultMode to set

See Also:

getResultMode()

setSortOrder

public void setSortOrder(FacetRequest.SortOrder sortOrder)

toString

public String toString()

Overrides:

toString in class Object