Specifying limit / offset for ContentProvider queries

Question

I'm trying to get my ContentResolver to run this query:

select * from myTable limit 1 offset 2

The only query method in ContentResolver is:

resolver.query(uri, projection, selection, selectionArgs, sortOrder);

I've tried:

final Cursor c = resolver.query(
        MyTable.CONTENT_URI,
        MyTable.PROJECTION,
        " ? ?",
        new String[] {"1", "2"},
        null);

Which just throws an IllegaLArgumentException. What is the correct way of achieving this?

Answer 1

I put the LIMIT clause in the sordOrder parameter, I've also seen the same thing done by others but not sure if its 100% correct:

final Cursor c = resolver.query(
        MyTable.CONTENT_URI,
        MyTable.PROJECTION,
        null,
        null,
        " limit 1 offset 2");

Answer 2

I put the limit clause as a query parameter using the syntax 'limit = offset, limit':

Cursor c = context.getContentResolver().query(
        MyTable.CONTENT_URI.buildUpon().encodedQuery("limit="+offset+","+limit).build(),
        MyTable.PROJECTION,
        null,
        null,
        null);

It works at least with MediaStore uris. Be careful of not encoding the "," or it won't work.

Answer 3

If you are providing your content provider, then you can use android.net.Uri.Builder#appendQueryParameter for providing limit and offset as query parameters, which the content provider can use while building the query.

public class MyProvider extends ContentProvider {
    public static final String QUERY_PARAMETER_LIMIT = "limit";
    public static final String QUERY_PARAMETER_OFFSET = "offset";

    public Cursor query(Uri uri, ...) {
        String limit = uri.getQueryParameter(QUERY_PARAMETER_LIMIT);
        String offset = uri.getQueryParameter(QUERY_PARAMETER_OFFSET);

        SQLiteQueryBuilder builder = new SQLiteQueryBuilder();

        // set the table name,...

        // leaving handling of null conditions as an exercise to the reader.
        String limitString = offset + "," + limit;

        Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, sortOrder, limitString);

        //...

        return c;
    }
}

while building the query:

private static final Uri CONTENT_URI = MyProvider.CONTENT_URI.buildUpon()
        .appendQueryParameter(MyProvider.QUERY_PARAMETER_LIMIT,
                    String.valueOf(limit))
        .appendQueryParameter(MyProvider.QUERY_PARAMETER_OFFSET,
                    String.valueOf(offset))
        .build();

note that the android.net.Uri.Builder#appendQueryParameter encodes the value to prevent sql injection.

References:

1. http://laviefrugale.blogspot.com/2012/01/using-limit-with-android-contentprovider.html
2. http://www.sqlite.org/lang_select.html
3. https://stackoverflow.com/a/12476458/1523910 + @eocanha's answer