How to change order in ordered+persisted collection?

views:

answers:

+2 Q:

How to change order in ordered+persisted collection?

I just need to change order of items in a (previously persisted) ordered collection...

I tried simply passing the re-arranged collection to a setter: after committing a transaction the collection is gone.
Then I tried to clear() the existing collection and addAll() afterwards: clear() makes persistent manager to mark all the elements as deleted. (But obviously I would like to be able to work with the collection items in the very transaction.)

(The collection is not in a default fetch group, so I tried the above also with the named fetch group added into the fetch plan. No luck.)

This must be the most stupid question, but I ran out of ideas and I'm stuck here two days already. I swear I googled. :(

+1 A:

The order of the data is set in an index. Unfortunately, the functionality to delete or reset the index is not currently there (http://stackoverflow.com/questions/2465195/how-to-delete-indexes-in-google-app-engine-java.

It may be possible to dynamically change the index, however. Take a look at http://rahulswackyworld.blogspot.com/2010/03/dynamic-indexes-with-google-app-engine.html.

Matthew Flynn 2010-05-25 03:25:56

Thank you. As long as it helps it will have to do, even though it sounds kinda weird that no one needed to change order of items in a collection.I'm using Java though, and given the linked solution works with Python it might not be that easy for me to implement. So, I was just thinking, do you think it makes even any sense to delete the parent object and re-create it with the collection-property re-arranged? (Other than that it would remain unchanged, identical key including.)

Jaroslav Záruba 2010-05-25 04:14:43

That might do it. Theoretically, it's an awful idea, but practically, it would probably work. The problem seems to be that google-data-store over simplifies collection relations and doesn't give an obvious way to vary the query that reads them (you should be able to use an order by in a query to get the collection in a given order, but this doesn't auto-wire nicely.

Matthew Flynn 2010-05-25 14:56:17

Yes, awful, I agree. I won't go that way anyways. Well, given I can't get official word from Google on this I think you gave me the answer.Thanks for your time, Matthew.

Jaroslav Záruba 2010-05-25 15:01:10

ansaurus

tags:

views:

answers:

How to change order in ordered+persisted collection?

related questions