When building a photo album feature similar to WeChat, I needed to read photos and videos with multi-folder switching — and it had to be faster than WeChat. After some research, the MediaStore approach proved most suitable. Since I hadn’t used it much before, this post serves as a record.

The GROUP BY Hack in ContentResolver

ContentResolver.query() does not expose a groupBy parameter (unlike SQLiteQueryBuilder.query()), but you can achieve a similar effect by embedding GROUP BY directly into the selection argument.

The trick relies on the fact that ContentResolver wraps the selection in parentheses during SQL compilation, producing WHERE ( ... ). By closing the parenthesis early in the selection string, you can append a GROUP BY clause.

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// Normal — selection becomes WHERE (mime_type IS NOT NULL)
MediaStore.Images.ImageColumns.MIME_TYPE + " IS NOT NULL "

// Hack — close the parenthesis and inject GROUP BY
MediaStore.Images.ImageColumns.MIME_TYPE + " IS NOT NULL "
    + ") GROUP BY (" + MediaStore.Images.ImageColumns.BUCKET_DISPLAY_NAME;

The resulting SQL looks like:

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WHERE (1=1) AND (mime_type IS NOT NULL) GROUP BY (bucket_display_name) ORDER BY ...

Warning: This approach may break on Android 10 (API 29) and above. The system MediaProvider injects additional conditions such as is_pending=0, is_trashed=0, and volume_name IN (...), which can incorrectly place the GROUP BY inside the WHERE clause. As of Android 14+, this hack is confirmed broken.

Modern Approach: Android 11+ Bundle Parameters

Starting with Android 11 (API 30), ContentResolver.query() supports structured query parameters via Bundle, eliminating the need for the hack above.

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Bundle queryArgs = new Bundle();
queryArgs.putStringArray(
    ContentResolver.QUERY_ARG_GROUP_COLUMNS,
    new String[]{MediaStore.Images.Media.BUCKET_DISPLAY_NAME}
);

Cursor cursor = contentResolver.query(
    MediaStore.Images.Media.EXTERNAL_CONTENT_URI,
    projection,
    queryArgs,
    null
);

Prefer QUERY_ARG_GROUP_COLUMNS (structured) over QUERY_ARG_SQL_GROUP_BY (raw SQL) for forward compatibility. The Provider indicates which arguments were honored via the Cursor’s EXTRA_HONORED_ARGS.

Workaround for Android 10

If you still need to support API 29, consider these alternatives:

  1. Use ContentResolver.query(uri, projection, selection, selectionArgs, sortOrder) with a subquery inline in the selection
  2. Client-side grouping — fetch all results and group in memory
  3. Custom ContentProvider — take full control of the SQL query logic

Caveats

  • The traditional selection hack behaves inconsistently across OEMs and Android versions — test thoroughly.
  • If your minSdkVersion is 30+, prioritize the Bundle approach.
  • When implementing a custom ContentProvider, use SQLiteQueryBuilder.query() directly — it natively supports groupBy and having parameters.

References