union
union(
catalogs: collections.abc.Sequence[PatchCatalog] ,
)-> ‘PatchCatalog’
Materialize several catalogs into one in-memory catalog.
Metadata rows are merged table-to-table (coord definitions deduplicate by def key); file-backed rows get absolute paths so members with different roots coexist, and the same source appearing in several members keeps a single entry (last one wins). For catalog views, only the selected patches transfer — note this respects row membership, not range trims; re-select on the result for exact envelopes.