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## org.apache.lucene.facet.index.streaming
Class CategoryParentsStream

    java.lang.Object
      org.apache.lucene.util.AttributeSource
          org.apache.lucene.analysis.TokenStream
              org.apache.lucene.analysis.TokenFilter
                  org.apache.lucene.facet.index.streaming.CategoryParentsStream

All Implemented Interfaces:
  Closeable

    public class CategoryParentsStream

extends TokenFilter

This class adds parents to a `CategoryAttributesStream`. The parents are added according to the `PathPolicy` and `OrdinalPolicy` from the `FacetIndexingParams` given in the constructor.
By default, category properties are removed when creating parents of a certain category. However, it is possible to retain certain property types using `addRetainableProperty(Class)`.

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

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
`AttributeSource.AttributeFactory, AttributeSource.State`

Field Summary
`protected CategoryAttribute` | `categoryAttribute` An attribute containing all data related to the category
`protected OrdinalProperty` | `ordinalProperty` A category property containing the category ordinal
`protected TaxonomyWriter` | `taxonomyWriter` A `TaxonomyWriter` for adding categories and retrieving their ordinals.

Fields inherited from class org.apache.lucene.analysis.TokenFilter
`input`

Constructor Summary
`CategoryParentsStream(CategoryAttributesStream input, TaxonomyWriter taxonomyWriter, FacetIndexingParams indexingParams)` Constructor.

Method Summary
`void` | `addRetainableProperty(Class<? extends CategoryProperty> toRetain)` Add a `CategoryProperty` class which is retained when creating parent tokens.
`protected void` | `clearCategoryProperties()` Clear the properties of the current `CategoryAttribute` attribute before setting the parent attributes.
`boolean` | `incrementToken()` Consumers (i.e., `IndexWriter`) use this method to advance the stream to the next token.

Methods inherited from class org.apache.lucene.analysis.TokenFilter
`close, end, reset`

Methods inherited from class org.apache.lucene.util.AttributeSource
`addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString`

Methods inherited from class java.lang.Object
`clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

### taxonomyWriter

    protected TaxonomyWriter taxonomyWriter

  A `TaxonomyWriter` for adding categories and retrieving their ordinals.

### categoryAttribute

    protected CategoryAttribute categoryAttribute

  An attribute containing all data related to the category

### ordinalProperty

    protected OrdinalProperty ordinalProperty

  A category property containing the category ordinal

Constructor Detail

### CategoryParentsStream

    public CategoryParentsStream(CategoryAttributesStream input,
                                 TaxonomyWriter taxonomyWriter,
                                 FacetIndexingParams indexingParams)

  Constructor.

  Parameters:
    `input` - The input stream to handle, must be derived from `CategoryAttributesStream`.
    `taxonomyWriter` - The taxonomy writer to use for adding categories and retrieving their ordinals.
    `indexingParams` - The indexing params used for filtering parents.

Method Detail

### incrementToken

    public final boolean incrementToken()
                                 throws IOException

  Description copied from class: `TokenStream`
  Consumers (i.e., `IndexWriter`) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate `AttributeImpl`s with the attributes of the next token.

  The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use `AttributeSource.captureState()` to create a copy of the current attribute state.

  This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to `AttributeSource.addAttribute(Class)` and `AttributeSource.getAttribute(Class)`, references to all `AttributeImpl`s that this stream uses should be retrieved during instantiation.

  To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in `TokenStream.incrementToken()`.

  Specified by:
    `incrementToken` in class `TokenStream`
  Returns:
    false for end of stream; true otherwise
  Throws:
    `IOException`

### clearCategoryProperties

    protected void clearCategoryProperties()

  Clear the properties of the current `CategoryAttribute` attribute before setting the parent attributes.
  It is possible to retain properties of certain types the parent tokens, using `addRetainableProperty(Class)`.

### addRetainableProperty

    public void addRetainableProperty(Class<? extends CategoryProperty> toRetain)

  Add a `CategoryProperty` class which is retained when creating parent tokens.

  Parameters:
    `toRetain` - The property class to retain.

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