Migrating from (now obsolete) custom ATImage content type

We had a whole collection of Plone 3 sites with a custom Image type subclassed from ATImage. This allowed us to add an extra image scaling to the standard list ("'logo':(454, 58)", used by our theme package).

While this still works in Plone 4, it isn't really the correct approach now that plone.app.imaging is part of the standard toolkit. That 开发者_运维问答can define custom scales on the fly.

It looks like I can enable plone.app.imaging on any type subclassed from ATImage by simply setting "sizes = None" for the collection of custom scales on the type. I am however then left with a redundant subclass of ATImage. Looking long term, it would be useful to replace all of our existing "FalconImage" content items (hundreds in total) with standard "Image" content items.

A brief experiment on a test site reveals that if I just walk through the document tree updating the portal_type attribute from "FalconImage" to "Image" then the content behaves as an "Image": each object suddenly acquires a Transform tab and all of the scales defined by @@imaging-controlpanel.

I am sure that there would be fallout from such a brute force approach. Is there a recommended approach for transforming one type into another?

(I'm happy to add source for our custom ATImage type if anyone thinks that it is relevant. It is really just a very minimal tweak of ATImage, with a different collection of sizes on the ImageField)

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Yes, there is a recommended approach:

http://pypi.python.org/pypi/Products.contentmigration

The only thing that you have to do is to write a custom migration from FalconImage to Image.

Bye, Giacomo

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You need to use Products.contentmigration but the docs there are no place to start. Use the docs at plone.org for a step-by-step on migrating content.

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Thanks to Giacomo and Ross for the pointers.

Just in case it is useful to others, my migration code ended up looking like the following:

from Products.contentmigration.walker import CustomQueryWalker
from Products.contentmigration.archetypes import InplaceATItemMigrator

class FalconImageMigrator(InplaceATItemMigrator):
    walker = CustomQueryWalker
    src_meta_type = "FalconImage"
    src_portal_type = "FalconImage"
    dst_meta_type = "ATBlob"
    dst_portal_type = "Image"

    # Following stolen from plone.app.blob.migrations, ATImageToBlobImageMigrator
    # migrate all fields except 'image', which needs special handling...
    fields_map = {
        'image': None,
    }

    def migrate_data(self):
        self.new.getField('image').getMutator(self.new)(self.old)

    # ATFileToBlobMigrator reindexes certain fields. Otherwise we
    # need to clear and rebuild the entire catalog.
    def last_migrate_reindex(self):
        self.new.reindexObject(idxs=['object_provides', 'portal_type',
           'Type', 'UID'])

migrator = FalconImageMigrator
walker   = migrator.walker(portal, FalconImageMigrator)

walker.go()
print walker.getOutput()

Complications:

1. Image is a little odd as a destination type, as data gets migrated into the blob store.

2. We need to update the catalog so that "resolveuid/UID" links generated by TinyMCE continue to work. last_migrate_reindex() method on Migrator class should be faster than clearing and rebuilding the entire catalog from scratch.