Sorting and paging a search across the whole mesh

A query with no path or namespace to pin it — nodeType:User, say — searches every partition at once. Two things you would reach for immediately did not work there.

sort:path failed with a database error. The union that gathers rows from every partition simply did not carry the path column, so there was nothing to sort by, however the underlying tables were built.

The second half was worse because it was silent. path:>"…" is how you ask for "the next page after this one", and the query language was folding it into the anchor — reading it as "the node whose path is exactly …", which nothing is. The answer came back empty, with no error. A routine that walks everything page by page therefore returned page one, saw an empty page two, and reported that it had finished. Two maintenance sweeps did exactly that in production before anyone noticed.

The cross-partition union now exposes the columns you can sort by, and a comparison on path stays a comparison instead of being mistaken for a location. Paging over the whole mesh works, and a walk that ends is a walk that really reached the end.