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Calibre implements lazy update of ebooks. If you update metadata for a book this is updated in the database but not inside the actual ebook file. When you send the ebook file the ebook file is updated in the sent copy of the ebook file. Possibly based on plugboards and/or when converted.
This means that ebook files don't have to be updated all the time. They can stay unchanged in their original pristine state. This is very good for safety reasons as well as for performance reasons. You may change metadata many times, for instance in batch jobs, but you might never actually send/save a copy of the ebook file. Or just a few times compared to how often you may update metadata. To update metadata in the database is very fast. To update metadata in the ebook file is very slow. In comparison, at least.
It is possible to to force calibre to update metadata inside the ebook files. In effect overwriting the original ebook file. Make sure you have good backups before you do that...
Last edited by Adoby; 12-12-2018 at 05:55 PM.
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