Source vs. Object

The relationship between sources and objects underlies Canon’s deduplication and archive tracking.

Sources Are Locations

When a root is scanned, Canon indexes every file it finds as a source. Each source represents a specific file at a specific path.

Objects Are Content

When sources are hashed, Canon creates or links them to objects. An object represents the underlying content, independent of where it was found.

Source A: /backup1/photos/IMG_001.jpg  ─┐
Source B: /backup2/old/IMG_001.jpg     ─┼─► Object (hash: abc123...)
Source C: /downloads/photo.jpg         ─┘

All three sources above have identical content, so they reference the same object.

Fact Sharing

When a source is linked to an object:

• Content facts (like EXIF metadata) can be stored on the object and become available to all sources with that hash
• Source facts (like file path) remain specific to each source

Import a fact once, and it is available everywhere that content exists.

Archive Tracking

Canon uses the source-object relationship to track archiving progress:

• When you archive a file, Canon copies it to an archive root and records the object’s hash
• Any source with that same hash is now considered “archived”
• The coverage command shows how many of your sources exist in an archive

Hashing

By default, Canon hashes all files during scanning. Since hashing can be time-consuming for large collections, you can:

• Use --no-hash during scan to skip hashing initially
• Hash selectively via the enrichment pipeline, targeting specific file types

Unhashed sources cannot be linked to objects, so they cannot be deduplicated or tracked for archive coverage.