Saving custom metadata when transferring between libraries

[africalass]

Hi

I have several libraries, and most have various custom columns. I like to have a 'my tags' column (so that I can download other peoples tags into the normal tags column, but as this creates thousands have a new one with a more finite amount).

I have just created a new library, and copied over a pile of documents from an old one using the 'delete after copy' option. Unfortunately I hadn't already created a custom 'my tags' column. I have since created the column, using the same titles as in the original library, but the tags have not appeared. Obviously this is my fault for doing it this way round and I'll know better in the future, but I do have a quick question:

* Is the old 'my tags' data still in there somewhere, and if so how could I restore it?
* If not, and the data is deleted when transferred to a new library without that column, is it possible to suggest that it could be kept as hidden metadata in case that column is created in the future? Just let me know if this isn't possible or desirable for any reason.

Thanks for your time.

Oh - on an unrelated issue, I have also had issues with Calibre crashing over the past few months that I've seen others report on occasion - if there is ever any data wanted from this just let me know. I have tried changing interface style and font etc.

[chaley]

Originally Posted by africalass

* Is the old 'my tags' data still in there somewhere, and if so how could I restore it?

You might be able to find it in a library backup, in particular in the OPF file.

* If not, and the data is deleted when transferred to a new library without that column, is it possible to suggest that it could be kept as hidden metadata in case that column is created in the future? Just let me know if this isn't possible or desirable for any reason.

This isn't something I would build. Reasons: There is no way to know which fields are important and which are not. There are be name conflicts, type conflicts, or value conflicts. There is no way to know when they should go away or whether they should propagate to further libraries. Too much of a can of worms. Of course, if someone else is interested in trying, have at it.

[africalass]

thanks for that. Appreciate the reply.

So am I correct in summarising that when I copy from one library to another that it looks for identical columns (including if I have custom created the same column in both libraries) to pass the data too. If that column doesn't exist in the new library (even if named differently by say, one letter) then the data is deleted.

Cheers

[chaley]

Originally Posted by africalass

thanks for that. Appreciate the reply.

So am I correct in summarising that when I copy from one library to another that it looks for identical columns (including if I have custom created the same column in both libraries) to pass the data too. If that column doesn't exist in the new library (even if named differently by say, one letter) then the data is deleted.

It looks for custom columns with the same name, type, and multiplicity. If it doesn't find such a column in the destination, then it doesn't copy that column's data.

One way to ensure that your libraries are structured the same (have the same custom columns and a few other options) is to check the "copy structure" option when you create new libraries.

[africalass]

Thanks, appeciated.

[FaceDeer]

I recently had some trouble making a backup of my library, the full path names of some of the books in it were too long for Windows to handle gracefully. I used a save template to create a nice compact backup folder instead that was easier to package up.

I was thinking, would it be a reasonable feature request to be able to create a new library using the metadata in an OPF file as a template to create custom columns from? That would make it a heck of a lot easier to import that backup package back into Calibre in the event that it's needed someday - I'd just need to grab an OPF from a fully-metadata-populated book, create a new library from it, and then import everything without fear that I'd lose metadata in the process. It'd make it easier to distribute libraries with fancy custom columns to others, too. Those long file paths played all sorts of havoc with some of the archive-making programs I tried, it really wasn't fun trying to work with the source library directory directly.

Or is there already an existing system I can use for recreating custom columns in a new library? That library settings backup .json file I sometimes see, perhaps?

Edit: For anyone who digs this thread up on the same quest as me, I've now learned through harsh necessity that the .json file does indeed contain everything needed to reproduce the structure of a database. One of my libraries got corrupted and restore-from-backup was failing. So I made a brand new blank library, copied the .json file from the corrupt one into it, "restored" the new library's database (which recreated all my custom columns) and then used "add book" to import all the books from the corrupt library into it. All nice and tidy again. I love how robust Calibre's handling of metadata is.