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https://issues.apache.org/jira/browse/LUCENE-9444?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17189618#comment-17189618
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Ankur edited comment on LUCENE-9444 at 9/2/20, 6:27 PM:
--------------------------------------------------------
Here is a patch that adds a new utility class
{code:java}
{code}
_TaxonomyFacetLabels_with a single method
{code:java}
getFacetLabelReader(LeafReaderContext){code}
that returns an instance of nested class
{code:java}
FacetLabelReader{code}
It uses an instance of
{code:java}
OrdinalsSegmentReader{code}
to fetch and decode ordinals for the input docid into a reusable buffer and
returns an
{code:java}
Iterator{code}
that uses
{code:java}
TaxonomyReader{code}
to lookup
{code:java}
FacetLabels{code}
for each ordinal.
The patch also adds a new test case
{code:java}
TestTaxonomyLabels{code}
demonstrating the usage.
was (Author: goankur):
Here is a patch that adds a new utility class - `TaxonomyFacetLabels` with the
method - `getFacetLabelReader(LeafReaderContext)` that returns an instance of
nested class - `FacetLabelReader`.
`FacetLabelReader` uses an instance of `OrdinalsSegmentReader` to fetch and
decode ordinals for the input docid into a reusable buffer and returns an
`Iterator` that uses `TaxonomyReader` instance to lookup `FacetLabels`.
The patch also adds a new test case `TestTaxonomyLabels` demonstrating the
usage.
> Need an API to easily fetch facet labels for a field in a document
> ------------------------------------------------------------------
>
> Key: LUCENE-9444
> URL: https://issues.apache.org/jira/browse/LUCENE-9444
> Project: Lucene - Core
> Issue Type: Improvement
> Components: modules/facet
> Affects Versions: 8.6
> Reporter: Ankur
> Priority: Major
> Labels: facet
> Attachments: LUCENE-9444.patch
>
>
> A facet field may be included in the list of fields whose values are to be
> returned for each hit.
> In order to get the facet labels for each hit we need to
> # Create an instance of _DocValuesOrdinalsReader_ and invoke
> _getReader(LeafReaderContext context)_ method to obtain an instance of
> _OrdinalsSegmentReader()_
> # _OrdinalsSegmentReader.get(int docID, IntsRef ordinals)_ method is then
> used to fetch and decode the binary payload in the document's BinaryDocValues
> field. This provides the ordinals that refer to facet labels in the
> taxonomy.**
> # Lastly TaxonomyReader.getPath(ord) is used to fetch the labels to be
> returned.
>
> Ideally there should be a simple API - *String[] getLabels(docId)* that hides
> all the above details and gives us the string labels. This can be part of
> *TaxonomyFacets* but that's just one idea.
> I am opening this issue to get community feedback and suggestions.
>
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