Android: SQLite, UI, caching and async queries

Question

I have a custom view that loads a model object (let's call it Person, why not). These objects are stored in a DB, obtained through a Loader and inserted into a ListView through a CursorAdapter that instantiates said views. So far, so good.

Now, Person has a reference to another model object, let's say Country. Countries are in its own table, and I need the name of the country (having the ID, of course) to represent it in the list items.

I see three options:

Query the database from the view method that loads the Person data (setPerson()?).
Deep pre-load (I think I just made a term up, sorry) my model objects with the Country information.
Request that the Country data be asynchronously queried and then brought back to the UI.

The problem with (1) is that the UI may block. The problem with (2) is that it leads to heavy data duplication in memory. The problem with (3) is that it complicates flow, maybe unnecessarily.

What should I do? Is the performance hit of (1) important? Maybe (1), query the data from the View, but implement a cache to avoid hitting the database repeatedly for the same Country? Maybe (2), with said cache layer to ensure instances of the object are unique? A 4th option I haven't considered? What do ORMs do?

Thanks!

Kurtis Nusbaum · Accepted Answer · 2011-10-28 21:28:57Z

2

In your query that you're using for your CursoLoader do an INNER JOIN on the Person and Country tables. The result of the query will then have all the information you want in the single cursor.

EDIT IN RESPONSE TO COMMENT

This is probably the best/cleanest way of going about things. Don't worry about duplication in memory at this point, that's a premature optimization. Besides, how big are your tables really going to be? Let's do a little back of the envelope calculation here. If each row of the joined table takes up 100 bytes (which is a huge row, so I'm thinking worse case scenario here), then even if you had 10000 rows in your result query (once again, that's preeeeetttty large), you'd only be using 1,000,000 bytes, or less than 1 meg of memory.

edited Oct 28, 2011 at 21:28

answered Oct 28, 2011 at 20:26

Kurtis Nusbaum

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