Facets in an online store seem simple until the first filter is selected.
In a catalog, they are part of the navigation. A selected color should not disappear from the list. Other colors should remain available: the user may want to switch to one or broaden the selection. Options with no matching products are more useful when shown as unavailable. Within a single facet, OR usually applies: red or blue. Across different facets, it is AND: brand, color, and size at the same time.
The difficult part begins after the first selection. Imagine a product catalog where the user has selected a brand, color, and size. The main result set must remain narrow and show only products matching all three conditions. But the filter panel follows different rules. It needs to preserve the selected color while also showing the colors the user can switch to under the same brand and size.
If every facet inherits all filters from the main query, it quickly collapses to the values already selected. If the filters for every facet have to be rebuilt manually, you end up with separate query branches for color, size, brand, availability, seller, and every other attribute.
Manticore Search 25.12.0 introduced facet_filter_mode, which moves this behavior into the facet API. A query can now describe how the store's filter panel should behave, without the application manually building nearly identical queries for every facet.
