Use ContentResolver.bulkInsert (Uri url, ContentValues[] values) instead of ApplyBatch()
ApplyBatch (1) uses transactions and (2) it locks the ContentProvider once for the whole batch instead locking/unlocking once per operation. because of this, it is slightly faster than doing them one at a time (non-batched).
However, since each Operation in the Batch can have a different URI and so on, there’s a huge amount of overhead. “Oh, a new operation! I wonder what table it goes in… Here, I’ll insert a single row… Oh, a new operation! I wonder what table it goes in…” ad infinitium. Since most of the work of turning URIs into tables involves lots of string comparisons, it’s obviously very slow.
By contrast, bulkInsert applies a whole pile of values to the same table. It goes, “Bulk insert… find the table, okay, insert! insert! insert! insert! insert!” Much faster.
It will, of course, require your ContentResolver to implement bulkInsert efficiently. Most do, unless you wrote it yourself, in which case it will take a bit of coding.