https://lucene.apache.org/solr/guide/7_2/collapse-and-expand-results.html#collapsing-query-parser

对应的源码实现QParserPlugin

static {

HashMap> map =newHashMap (30, 1);

map.put(LuceneQParserPlugin.NAME, LuceneQParserPlugin.class);

map.put(FunctionQParserPlugin.NAME, FunctionQParserPlugin.class);

map.put(PrefixQParserPlugin.NAME, PrefixQParserPlugin.class);

map.put(BoostQParserPlugin.NAME, BoostQParserPlugin.class);

map.put(DisMaxQParserPlugin.NAME, DisMaxQParserPlugin.class);

map.put(ExtendedDismaxQParserPlugin.NAME, ExtendedDismaxQParserPlugin.class);

map.put(FieldQParserPlugin.NAME, FieldQParserPlugin.class);

map.put(RawQParserPlugin.NAME, RawQParserPlugin.class);

map.put(TermQParserPlugin.NAME, TermQParserPlugin.class);

map.put(TermsQParserPlugin.NAME, TermsQParserPlugin.class);

map.put(NestedQParserPlugin.NAME, NestedQParserPlugin.class);

map.put(FunctionRangeQParserPlugin.NAME, FunctionRangeQParserPlugin.class);

map.put(SpatialFilterQParserPlugin.NAME, SpatialFilterQParserPlugin.class);

map.put(SpatialBoxQParserPlugin.NAME, SpatialBoxQParserPlugin.class);

map.put(JoinQParserPlugin.NAME, JoinQParserPlugin.class);

map.put(SurroundQParserPlugin.NAME, SurroundQParserPlugin.class);

map.put(SwitchQParserPlugin.NAME, SwitchQParserPlugin.class);

map.put(MaxScoreQParserPlugin.NAME, MaxScoreQParserPlugin.class);

map.put(BlockJoinParentQParserPlugin.NAME, BlockJoinParentQParserPlugin.class);

map.put(BlockJoinChildQParserPlugin.NAME, BlockJoinChildQParserPlugin.class);map.put(CollapsingQParserPlugin.NAME, CollapsingQParserPlugin.class);map.put(SimpleQParserPlugin.NAME, SimpleQParserPlugin.class);

map.put(ComplexPhraseQParserPlugin.NAME, ComplexPhraseQParserPlugin.class);

map.put(ReRankQParserPlugin.NAME, ReRankQParserPlugin.class);

map.put(ExportQParserPlugin.NAME, ExportQParserPlugin.class);

map.put(MLTQParserPlugin.NAME, MLTQParserPlugin.class);

map.put(HashQParserPlugin.NAME, HashQParserPlugin.class);

map.put(GraphQParserPlugin.NAME, GraphQParserPlugin.class);

map.put(XmlQParserPlugin.NAME, XmlQParserPlugin.class);

map.put(GraphTermsQParserPlugin.NAME, GraphTermsQParserPlugin.class);

map.put(IGainTermsQParserPlugin.NAME, IGainTermsQParserPlugin.class);

map.put(TextLogisticRegressionQParserPlugin.NAME, TextLogisticRegressionQParserPlugin.class);

map.put(SignificantTermsQParserPlugin.NAME, SignificantTermsQParserPlugin.class);

map.put(PayloadScoreQParserPlugin.NAME, PayloadScoreQParserPlugin.class);

map.put(PayloadCheckQParserPlugin.NAME, PayloadCheckQParserPlugin.class);

map.put(BoolQParserPlugin.NAME, BoolQParserPlugin.class);

standardPlugins = Collections.unmodifiableMap(map);

}

具体如下：

/** The <b>CollapsingQParserPlugin</b> 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.

<p>

Sample syntax:

<p>

Collapse based on the highest scoring document:

<p>

fq=(!collapse field=field_name}

<p>

Collapse based on the min value of a numeric field:

<p>

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

<p>

Collapse based on the max value of a numeric field:

<p>

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

<p>

Collapse with a null policy:

<p>

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

<p>

There are three null policies: <br>

ignore : removes docs with a null value in the collapse field (default).<br>

expand : treats each doc with a null value in the collapse field as a separate group.<br>

collapse : collapses all docs with a null value into a single group using either highest score, or min/max.

<p>

The CollapsingQParserPlugin fully supports the QueryElevationComponent

**/