Currently, the main sstable data parsing entry point data_consume_rows()
takes a contiguous range of bytes to read from disk and parse. This range
is supposed to be an entire partition or contiguous group of partitions.
and is self contained (can be parsed without extra information about the
identity of these partitions).
For the promoted index feature (which we will add in a following patch)
we will want the range to span only a part of a partition, and will need
the caller to provide some information not available to the parser (such
as the partition's key). In the future, we will also want to support a
vector of byte ranges, instead of just one.
So in preparation for this, this patch simply replaces the start/end pair
by a new class disk_read_range, which can be easily extended in later
patches. No new functionality is introduced in this patch.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>