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Android SQLITE search VS ArrayList search for small amount of dataset

Suppose, In my app I have a sqlite table that can contain at most 20 row. Each row has 2 column(id, name). Where I frequently need to search by Id to get Name. For this frequent need I have two solution:
Solution 1: Get rows in a arraylist<model> and then find name from array.
Solution 2: Every time search on sqlite table.
Now please give your opinion which one is better?
Remember again, I need this search in my recycleView item, so it call so frequently.
Thanks

I don't really get what is your real intent, but if your task is to search by id often, I would use
LongSparseArray<String> idsToNames; // or LongSparseArray<Model>
Which will map primitive long to Strings in a more memory-efficient way than Map and will have a better performance than ArrayList when searching.
The advantage over querying SQLite here is that you can do it in a blocking manner instead of having to query database on a background thread every time the lookup runs.
The disadvantage is that whenever data changes in SQLite, you will have to rebuild your idsToNames map. Also, if the number of entries in SQLite will eventually grow, you will end up in a large collection. So I would recommend this approach only if the updates to the database during this session will not happen, and if the data size is always predictable or fixed.

In Android SQLite, working directly with Cursor is more memory efficient than creating Model Objects?

In most of the Android sample codes, populating a ListView from SQLite database is done in two ways,
Prefetch data to List - Execute query, create Model objects for each row then add it to a List and close the Cursor, then populate ListView with List.
Without List and Model objects - Execute query and populate ListView by following the Cursor using moveToFirst, moveToLast, move, as required.
Now I want to know, which of the above method is more memory efficient, in Android ?

The Cursor approach is more memory efficient:
Suppose you have 1000 entries in your database and you have a ListView which can show 10 entries at the same time. If you create a list at first, you'll have to create 1000 model objects (each of which in turn consists of several objects depending on the number of columns of your table) and the listview creates additional 10 views (actually some more, depending on the layout of the list) for displaying the 10 items. Now when the user scrolls the list, in your Adapter you end up copying data from your model objects to the list item views currently in view.
On the other hand, if you use a CursorAdapter, whenever you have to fill a list item with data, you are provided with the Cursor holding exactly the data for that row and you can simply pick the data of the columns you actually need to be displayed in the list item. No need for creating the 1000 model objects.
From a code readability perspective, a model approach would be better because working with Cursors is quite low level, you'll need to know the names of the columns in the database and so on.

I think you need to use Service or at least Thread/Async so your UI thread will not be blocked. Service is better because people can go to other apps while downloading. You can use BroadcastReceiver to communicate with your running Service.

Which adapter choose?

I have two methods which read the same data from database, the first returns Cursor and the second returns List of objects.Now I show my items in activity using SimpleCursorAdapter and the first method, byt I can also use the second method and appropriate adapter.
Which of these two ways is beter to use and in the second way which adapter I should use?
P.S sorry for poor english

Definitely go with SimpleCursorAdapter. If possible, always use Cursor if your data comes from database, you save memory by not creating List of objects. Creating objects in Java is expensive with regards to time and memory consumption and you have to bear in mind you are on mobile platform with limited resources. If you are using List of objects for your ListView than use custom adapter extending from ArrayAdapter.
It's not always straightforward to use Cursor although your data comes from database. Let's say you store places in the database defined by its name and location and you want to display them in a ListView sorted by distance from current location. It makes it difficult to execute a query which returns sorted results unless you don't store relative distance in additional column. But you can get Cursor convert it to List of objects and sort this collection before sending it to your ListView.

Async task with SimpleCursorList (Android sql select)

I'm relatively new to Android but I just cant google this. I have following situation:
quite large SQL db on android (need to select and load about 2000 records to ListActivity)
I use SimpleCursorAdapter so far BUT... it doesn't allow me to load data asynchronously with AsyncTask (SimpleCursorAdapter has no "add()" as e.g. ArrayAdapter does)
I know how to make it work with ArrayAdapter but then I lose the ID attribute every time the time is clicked and I want to do it the "clean" way and keep the id (not save it some place hidden)
===> For now user has to wait till all db output is parsed into GUI, it takes some time. How can I fix it to make it run faster ? I need something like SimpleCursorAdapter.add(item) or extend it but not sure ...
thnx

You should consider having some pagination mechanism, not loading everything in an ArrayAdapter but better, returning a simpleCursorAdapter with just a subset of size N of your records. When the user will reach the last row, display a button to increase N and refetch the data from your database.

Android: SQLite, UI, caching and async queries

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!

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.