(feat) Add prefix and regex filtering for term facets

[ajroetker]

This change adds support for filtering facet terms by prefix and/or regex pattern. Which is useful for faceting during search_as_you_type style faceting for terms that match what is in the searchbox, aggregated by field (for books I can facet facet authors, titles etc in an autosuggest a bit cleaner now).

• Adds TermPrefix and TermPattern fields to FacetRequest
• Updated NewTermsFacetBuilder to return error
• Only matching terms trigger string allocation from []byte

[Copilot]

Pull Request Overview

This PR adds prefix and regex filtering capabilities to term facets in Bleve's search functionality, enabling search-as-you-type style faceting where terms can be filtered to match patterns during aggregation.

Key changes:

• Added TermPrefix and TermPattern fields to FacetRequest struct for filtering configuration
• Modified NewTermsFacetBuilder to accept prefix and pattern parameters and return an error for invalid regex patterns
• Optimized UpdateVisitor to perform zero-allocation prefix and regex matching on []byte before converting to string

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
search.go	Added TermPrefix and TermPattern fields to FacetRequest for API support
search/facet/facet_builder_terms.go	Implemented prefix/regex filtering logic with optimized byte-level matching
index_impl.go	Updated to pass prefix and pattern parameters to NewTermsFacetBuilder and handle errors
search/collector/topn_test.go	Updated test to handle new error-returning signature of NewTermsFacetBuilder
search/facet/facet_builder_terms_test.go	Added comprehensive test coverage for prefix, regex, combined filtering, and edge cases

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[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

Comments suppressed due to low confidence (1)

search/facet/facet_builder_terms.go:122

• The missing counter may not accurately reflect documents without matching values when filters are active. A document with terms that don't match the filters will be counted as "missing" even though it has values for the field. Consider whether this is the intended behavior or if missing should only count documents that truly have no value for the field, regardless of filters.

If the current behavior is intentional (i.e., "missing" means "no matching values"), the documentation should be updated to clarify this semantic change when filters are applied.

}

func (fb *TermsFacetBuilder) EndDoc() {
	if !fb.sawValue {
		fb.missing++
	}
}

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[abhinavdangeti]

This is great, thanks for this @ajroetker .