SharePoint's default for a text property is word breaking, so ours is too:
every keyword field gets the _words sibling unless it opts out with
NoWordBreaker, which now carries SharePoint's polarity as well. Artist,
album, camera model and the other facets match by word like name and title;
tags and favorites stay one label, ids, paths and the mime type one value.
KQL searches case-insensitively, so every keyword field gets its lowercased
search sibling unless it opts out: ids are opaque, paths are POSIX, the mime
type is normalized already. That takes the facets along, artist or camera
model match regardless of case, while the case-preserved base still answers
and aggregates. Which siblings a field carries is decided once, from the
struct and the overrides, and the renderers, the document writer and the
query lowering all read it from there.
Build the bleve and OpenSearch index mappings from the Go struct via
reflection (json tags + per-field overrides) instead of hand-rolled
mappings and hit deserializers. New mapping package: BleveBuildMapping,
OpenSearchBuildMapping, Deserialize[T], PrepareForIndex; field decoding is
fail-soft. Mtime is typed as a date so mtime ranges are chronological on
both backends. Route CS3 facet parsing through mapping.DeserializeStringMap.
The any-valued (bleve hit) and string-valued (CS3 metadata) deserializers
share one generic fillStruct walker with a per-value setLeaf callback.
Dominik Schmidt