// Take as much as possible from the source bucket, sort it in memory and dump to destination bucket.
// Return 1 if there is more data available in the source bucket.
int (*internal_sort)(struct sort_context *ctx, struct sort_bucket *in, struct sort_bucket *out, struct sort_bucket *out_only);
// Take as much as possible from the source bucket, sort it in memory and dump to destination bucket.
// Return 1 if there is more data available in the source bucket.
int (*internal_sort)(struct sort_context *ctx, struct sort_bucket *in, struct sort_bucket *out, struct sort_bucket *out_only);