org.apache.solr.search

Class CollapsingQParserPlugin

java.lang.Object

org.apache.solr.search.QParserPlugin

org.apache.solr.search.CollapsingQParserPlugin

All Implemented Interfaces:

SolrInfoBean, NamedListInitializedPlugin

public class CollapsingQParserPlugin
extends QParserPlugin

The CollapsingQParserPlugin is a PostFilter that performs field collapsing. This is a high performance alternative to standard Solr field collapsing (with ngroups) when the number of distinct groups in the result set is high.

Sample syntax:

Collapse based on the highest scoring document:

fq=(!collapse field=field_name}

Collapse based on the min value of a numeric field:

fq={!collapse field=field_name min=field_name}

Collapse based on the max value of a numeric field:

fq={!collapse field=field_name max=field_name}

Collapse with a null policy:

fq={!collapse field=field_name nullPolicy=nullPolicy}

There are three null policies:
ignore : removes docs with a null value in the collapse field (default).
expand : treats each doc with a null value in the collapse field as a separate group.
collapse : collapses all docs with a null value into a single group using either highest score, or min/max.

The CollapsingQParserPlugin fully supports the QueryElevationComponent

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CollapsingQParserPlugin.CollapseScore
static class	CollapsingQParserPlugin.CollapsingPostFilter
static class	CollapsingQParserPlugin.GroupHeadSelector Models all the information about how group head documents should be selected
static class	CollapsingQParserPlugin.GroupHeadSelectorType
static class	CollapsingQParserPlugin.NullPolicy

Nested classes/interfaces inherited from interface org.apache.solr.core.SolrInfoBean

SolrInfoBean.Category, SolrInfoBean.Group

Field Summary

Fields

Modifier and Type	Field and Description
static String	COLLECT_ELEVATED_DOCS_WHEN_COLLAPSING If elevation is used in combination with the collapse query parser, we can define that we only want to return the representative and not all elevated docs by setting this parameter to false (true by default).
static String	HINT_BLOCK Indicates that values in the collapse field are unique per contiguous block, and a single pass "block based" collapse algorithm can be used.
static String	HINT_MULTI_DOCVALUES Deprecated.
static String	HINT_TOP_FC
static String	NAME
static String	NULL_COLLAPSE Deprecated. use CollapsingQParserPlugin.NullPolicy instead.
static String	NULL_EXPAND Deprecated.
static String	NULL_IGNORE Deprecated.

Fields inherited from class org.apache.solr.search.QParserPlugin

DEFAULT_QTYPE, standardPlugins

Constructor Summary

Constructors

Constructor and Description
CollapsingQParserPlugin()

Method Summary

Modifier and Type	Method and Description
QParser	createParser(String qstr, SolrParams localParams, SolrParams params, SolrQueryRequest request) return a QParser
static LeafReader	getTopFieldCacheReader(SolrIndexSearcher searcher, String collapseField) This forces the use of the top level field cache for String fields.
static Sort	rewriteSort(SortSpec sortSpec, IndexSearcher searcher) Helper method for rewriting the Sort associated with a SortSpec.

Methods inherited from class org.apache.solr.search.QParserPlugin

getCategory, getDescription, getMetricNames, getName, init

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.solr.core.SolrInfoBean

getMetricRegistry, getMetricsSnapshot, registerMetricName

Field Detail

NAME

public static final String NAME

See Also:

Constant Field Values

HINT_TOP_FC

public static final String HINT_TOP_FC

See Also:

Constant Field Values

HINT_BLOCK

public static final String HINT_BLOCK

Indicates that values in the collapse field are unique per contiguous block, and a single pass "block based" collapse algorithm can be used. This behavior is the default for collapsing on the _root_ field, but may also be enabled for other fields that have the same characteristics. This hint will be ignored if other options prevent the use of this single pass approach (notable: nullPolicy=collapse)

Do NOT use this hint if the index is not laid out such that each unique value in the collapse field is garuntteed to only exist in one contiguous block, otherwise the results of the collapse filter will include more then one document per collapse value.

See Also:

Constant Field Values

COLLECT_ELEVATED_DOCS_WHEN_COLLAPSING

public static String COLLECT_ELEVATED_DOCS_WHEN_COLLAPSING

If elevation is used in combination with the collapse query parser, we can define that we only want to return the representative and not all elevated docs by setting this parameter to false (true by default).

NULL_COLLAPSE

@Deprecated
public static final String NULL_COLLAPSE

Deprecated. use CollapsingQParserPlugin.NullPolicy instead.

See Also:

Constant Field Values

NULL_IGNORE

@Deprecated
public static final String NULL_IGNORE

Deprecated.

See Also:

Constant Field Values

NULL_EXPAND

@Deprecated
public static final String NULL_EXPAND

Deprecated.

See Also:

Constant Field Values

HINT_MULTI_DOCVALUES

@Deprecated
public static final String HINT_MULTI_DOCVALUES

Deprecated.

See Also:

Constant Field Values

Constructor Detail

CollapsingQParserPlugin

public CollapsingQParserPlugin()

Method Detail

createParser

public QParser createParser(String qstr,
                            SolrParams localParams,
                            SolrParams params,
                            SolrQueryRequest request)

Description copied from class: QParserPlugin

return a QParser

Specified by:

createParser in class QParserPlugin

getTopFieldCacheReader

public static LeafReader getTopFieldCacheReader(SolrIndexSearcher searcher,
                                                String collapseField)

This forces the use of the top level field cache for String fields. This is VERY fast at query time but slower to warm and causes insanity.

rewriteSort

public static Sort rewriteSort(SortSpec sortSpec,
                               IndexSearcher searcher)
                        throws IOException

Helper method for rewriting the Sort associated with a SortSpec. Handles the special case default of relevancy sort (ie: a SortSpec w/null Sort object)

Throws:

IOException