Instead of requiring the user to subclass a "sstable_creator" class to
specify how to create a new sstable (or in the future, several of them),
switch to an std::function.
In practice, it is much easier to specify a lambda than a class, especialy
since C++11 made it easy to capture variables into lambdas - but not into
local classes.
The "commit()" function is also unnecessary. Then intention there was to
provide a function to "commit" the new sstables (i.e., rename them).
But the caller doesn't need to supply this function - it can just wait
for the future of the end of compaction, and do his own committing code
right then.
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
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