Extractors wrote whatever the file said, so one person held several rows:
"Sam Newman" beside "Newman, Sam;" beside "Sam Newman.epub", the last because
the upload path never stripped the file extension. Tidy on write, in the
validator and in the uniqueness lookup alike, and merge the rows that collide.
"Building Microservices, 2E" never matched "Building Microservices". Key the
strip on the trailing "e" so 2E, 5e and 3 Ed are caught, while a bare number
leaves "Catch 22" and "Blade Runner 2049" alone. Stored keys are recomputed.
DC:identifier was validated verbatim, so hyphenated and urn:isbn: forms never
reached the checksum and every non-ISBN identifier was discarded. Normalise
first, and name whatever survives.
Reduce a title, an author and an identifier to a single comparison key, so
two copies of one book can be recognised by equality rather than by a
similarity score.
patrick