5. ZOOM Facets

Facets are only supported for a few Z39.50 targets. It is a relatively new non-standard Z39.50 extension (see facets.asn in the YAZ source). However, facets are usually supported for Solr and SRU 2.0 targets.

Facets may be specified by the facets option before a search is sent. See Section 8, “Facets” for the notation. For inspection of the returned facets, the following functions are available:

    ZOOM_facet_field *ZOOM_resultset_facets(ZOOM_resultset r);

    size_t ZOOM_resultset_facets_size(ZOOM_resultset r);

    ZOOM_facet_field ZOOM_resultset_get_facet_field(ZOOM_resultset r,
                                                    const char *facet_name);

    ZOOM_facet_field ZOOM_resultset_get_facet_field_by_index(ZOOM_resultset r,
                                                             int pos);

    const char *ZOOM_facet_field_name(ZOOM_facet_field facet_field);

    size_t ZOOM_facet_field_term_count(ZOOM_facet_field facet_field);

    const char *ZOOM_facet_field_get_term(ZOOM_facet_field facet_field,
                                          size_t idx, int *freq);

References to temporary structures are returned by all functions. They are only valid as long the Result set is valid.

All facet fields may be returned by a call to ZOOM_resultset_facets. The length of the array is given by ZOOM_resultset_facets_size. The array is zero-based and the last entry will be at ZOOM_resultset_facets_size(result_set)-1.

Facet fields can also be fetched via its name using ZOOM_resultset_get_facet_field. Or by its index (starting from 0) by a call to ZOOM_resultset_get_facet_field_by_index. Both of these functions return NULL if name is not found or index is out of bounds.

Function ZOOM_facet_field_name gets the request facet name from a returned facet field.

Function ZOOM_facet_field_get_term returns the idx'th term and term count for a facet field. Idx must between 0 and ZOOM_facet_field_term_count-1, otherwise the returned reference will be NULL. On a valid idx, the value of the freq reference will be the term count. The freq parameter must be valid pointer to integer.