Why Faceted Search Returns Zero Results and How to Engineer Around It

Faceted search interfaces promise that every selectable filter leads to real results, but poor implementation of filter logic frequently breaks that promise. The core issue lies in how facet counts are computed: each facet's counts must be calculated against the result set excluding that facet's own filters, otherwise selecting one value causes all related options to show zero. Within a single facet, multiple selections should use OR logic, while filters across different facets should use AND, and reversing this causes counts that users cannot reconcile. Hierarchical facets add further complexity, requiring parent-level counts to include all child documents so numbers remain consistent as users drill deeper. Mathematically, applying just four to five independent filters on a 50,000-product catalogue can reduce expected results to fewer than 45 items, and real-world filter correlations make zero-result outcomes even more likely, meaning the interface must be designed to handle heavy filtering as a routine case.