find_in_batches の中で destroy とかしても普通に動くから、不思議に思ってソースを見てみたらきちんと配慮されてた。。
Yields each batch of records that was found by the find options as an array. The size of each batch is set by the :batch_size option; the default is 1000. You can control the starting point for the batch processing by supplying the :start option. This is especially useful if you want multiple workers dealing with the same processing queue. You can make worker 1 handle all the records between id 0 and 10,000 and worker 2 handle from 10,000 and beyond (by setting the :start option on that worker). It’s not possible to set the order. That is automatically set to ascending on the primary key (“id ASC”) to make the batch ordering work. This also mean that this method only works with integer-based primary keys. You can’t set the limit either, that’s used to control the batch sizes. Example: Person .where ("age > 21" ).find_in_batches do | group | sleep (50 ) # Make sure it doesn...