Keyword and path fields always index their case-preserved base and, when CaseInsensitive is set, an additional <field>_lowercase sibling used only for matching. The KQL lowering marks a restriction case-insensitive; each backend searches the sibling and lowercases the query value the same way the sibling is precomputed at index time (Go strings.ToLower on both sides, so non-ASCII stays consistent).
Search always returns the case-preserved base, so the sibling never has to be read back. In bleve it is indexed but not stored, kept out of _all, and without doc values. In OpenSearch it deliberately stays in _source: excluding it would make every update-by-query script rebuild all siblings from the document via painless toLowerCase, which lowercases differently than Go and would drift from the query side. Keeping it in _source avoids that, and a lowercased copy of a name or path is negligible disk in a cluster.
The OpenSearch move script keeps the base and its sibling in sync by swapping the moved prefix in Path_lowercase and setting Name_lowercase from Go-lowercased params, so case-insensitive search still finds a file after it moves (previously the sibling went stale). bleve re-indexes the whole document on move/delete/restore, so its siblings stay fresh for free.
This also repairs OpenSearch path search (the query value was no longer folded to lowercase, so path:<Foo> returned nothing) and makes bleve path queries match a folder and its descendants like OpenSearch's path_hierarchy. The Path base stays case-preserved so the move/delete descendant update (an exact TermQuery on Path) matches mixed-case folders.
Add a TypeGeopoint field type. The libregraph Location facet is kept as an
object (retrieval / numeric queries) and a sibling <name>_geopoint field
carries the {lat,lon} form for geo-distance / bbox / polygon queries,
uniform across bleve and OpenSearch via the shared mapping. PrepareForIndex
splices the sibling in at write time.
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