Petr Gusev a46df5af63 row_cache: pass partition_start though nonforwardable reader ...

Now the nonforwardable reader unconditionally produces
a partition_end, even if the input reader was empty.
This is strange in itself, but it also hinders to
properly fix its next_partition() method, which is
our ultimate goal. So we are going to change this
and produce partition_end only if there were some
data in the stream. However, this makes a problem:
now we pop partition_start from the underlying reader
in autoupdating_underlying_reader::move_to_next_partition
and manually push it back to downstream readers
bypassing nonforwardable reader. This means if we
change the logic in nonforwardable reader as described
we will end up with partition_start without partition_end
in the downstream readers.

This patch rectifies this by making sure that
nonforwardable will see the initial partition_start.
We inject this partition_start just before the
nonforwardable reader, into delegating_reader.
This also makes the result type of
range_populating_reader::operator() a bit simpler,
we don't need to pass partition_start anymore.

2023-02-27 18:46:31 +04:00

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