Nadav Har'El 6cf44f6817 Optimize column_family::make_sstable_reader() for one partition ...

This patch does the same thing to column_family::make_sstable_reader() as
commit 186f031 did to sstable::as_mutation_source().

Although usually one can fast_forward_to() on the result of a
column_family::make_sstable_reader(), earlier we had an optimization
where if a single partition was specified, it was read exactly,
and fast_forward_to() was *NOT* allowed.

With the mutation_reader::forwarding flag patch, when this flag
was on - requesting fast_forward_to() - we disabled this optimization.
This makes sense, but is not backward compatible with the code which
previously assumes this optimization exists. In particular,
column_family::data_query() does a single partition read but does not
specify forwarding::no explicitly.
So this patch returns this optimization, despite this meaning that we
blatently ignore the fwd_mr flag in that case.

Fixes #2524.

Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20170626141121.30322-1-nyh@scylladb.com>

2017-06-26 17:13:03 +03:00

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