pub fn key_map(reader: &Reader, column: usize) -> Option<KeyMap>Expand description
The key map this table carries for a column, when it carries one this build can use.
None covers every reason there is not one, and covering them all is the point rather than an
omission. Section 3.1 says deleting every graph section changes no answer, only the time, so
there is no reason to distinguish no map was ever built from the map is stale, the payload
does not checksum, or the form is one a later build invented: the answer to all four is to
run the query the way it ran before key maps existed. A caller that wants to know which it was
reads the entry out of crate::Table::sections, which is where rudb_links() will look.