org.apache.solr.response.transform

Class DocTransformer

java.lang.Object

org.apache.solr.response.transform.DocTransformer

Direct Known Subclasses:

BaseEditorialTransformer, DocTransformers, RenameFieldTransformer, ScoreAugmenter, ValueSourceAugmenter

public abstract class DocTransformer
extends Object

A DocTransformer can add, remove or alter a Document before it is written out to the Response. For instance, there are implementations that can put explanations inline with a document, add constant values and mark items as being artificially boosted (see QueryElevationComponent)

New instance for each request

See Also:

TransformerFactory

Field Summary

Fields

Modifier and Type	Field and Description
protected ResultContext	context

Constructor Summary

Constructors

Constructor and Description
DocTransformer()

Method Summary

Modifier and Type	Method and Description
String[]	getExtraRequestFields() When a transformer needs access to fields that are not automatically derived from the input fields names, this option lets us explicitly say the field names that we hope will be in the SolrDocument.
abstract String	getName()
boolean	needsSolrIndexSearcher() Indicates if this transformer requires access to the underlying index to perform it's functions.
void	setContext(ResultContext context) This is called before transform(org.apache.solr.common.SolrDocument, int, float) to provide context for any subsequent transformations.
String	toString()
abstract void	transform(SolrDocument doc, int docid, float score) This is where implementations do the actual work.

Methods inherited from class java.lang.Object

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

Field Detail

context

protected ResultContext context

Constructor Detail

DocTransformer

public DocTransformer()

Method Detail

getName

public abstract String getName()

Returns:

The name of the transformer

setContext

public void setContext(ResultContext context)

This is called before transform(org.apache.solr.common.SolrDocument, int, float) to provide context for any subsequent transformations.

Parameters:

context - The ResultContext stores information about how the documents were produced.

See Also:

needsSolrIndexSearcher()

needsSolrIndexSearcher

public boolean needsSolrIndexSearcher()

Indicates if this transformer requires access to the underlying index to perform it's functions. In some situations (notably RealTimeGet) this method may be called before setContext(org.apache.solr.response.ResultContext) to determine if the transformer must be given a "full" ResultContext and accurate docIds that can be looked up using ResultContext.getSearcher(), or if optimizations can be taken advantage of such that ResultContext.getSearcher() may return null, and docIds passed to transform(org.apache.solr.common.SolrDocument, int, float) may be negative. The default implementation always returns false.

See Also:

ResultContext.getSearcher(), transform(org.apache.solr.common.SolrDocument, int, float)

transform

public abstract void transform(SolrDocument doc,
                               int docid,
                               float score)
                        throws IOException

This is where implementations do the actual work. If implementations require a valid docId and index access, the needsSolrIndexSearcher() method must return true

Parameters:

doc - The document to alter

docid - The Lucene internal doc id, or -1 in cases where the doc did not come from the index

score - the score for this document

Throws:

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

See Also:

needsSolrIndexSearcher()

getExtraRequestFields

public String[] getExtraRequestFields()

When a transformer needs access to fields that are not automatically derived from the input fields names, this option lets us explicitly say the field names that we hope will be in the SolrDocument. These fields will be requested from the SolrIndexSearcher but may or may not be returned in the final QueryResponseWriter

Returns:

a list of extra lucene fields

toString

public String toString()

Overrides:

toString in class Object