Products.BTreeFolder2-3.0-1.lbn25.noarch

BTreeFolder2 is a Zope product that acts like a Zope 2 OFS folder but can store many more items.

When you fill a Zope folder with too many items, both Zope and your browser get overwhelmed. Zope has to load and store a large folder object, and the browser has to render large HTML tables repeatedly. Zope can store a lot of objects, but it has trouble storing a lot of objects in a single standard folder.

Zope Corporation once had an extensive discussion on the subject. It was decided that we would expand standard folders to handle large numbers of objects gracefully. Unfortunately, Zope folders are used and extended in so many ways today that it would be difficult to modify standard folders in a way that would be compatible with all Zope products.

So the BTreeFolder product was born. It stored all subobjects in a ZODB BTree, a structure designed to allow many items without loading them all into memory. It also rendered the contents of the folder as a simple select list rather than a table. Most browsers have no trouble rendering large select lists.

But there was still one issue remaining. BTreeFolders still stored the ID of all subobjects in a single database record. If you put tens of thousands of items in a single BTreeFolder, you would still be loading and storing a multi-megabyte folder object. Zope can do this, but not quickly, and not without bloating the database.

BTreeFolder2 solves this issue. It stores not only the subobjects but also the IDs of the subobjects in a BTree. It also batches the list of items in the UI, showing only 1000 items at a time. So if you write your application carefully, you can use a BTreeFolder2 to store as many items as will fit in physical storage.

There are products that depend on the internal structure of the original BTreeFolder, however. So rather than risk breaking those products, the product has been renamed. You can have both products installed at the same time. If you’re developing new applications, you should use BTreeFolder2.