Function mz_storage::render::upsert::rehydrate

fn rehydrate(
    key_indices_map: &BTreeMap<usize, usize>,
    key: &Row,
    thinned_value: &Row,
    row_buf: &mut Row,
    kdv: &mut DatumVec
) -> Row

rehydrate uses information from the source description to find which indices in the row are keys and add them back in in the right places. key_indices is a map from the each key-part’s index in the value to its index in the key.