Currently, if sstable::write_components() is called to write a new sstable
using the same generation of a sstable that exists, a temporary TOC will
be unconditionally created. Afterwards, the same sstable::write_components()
will fail when it reaches sstable::create_data(). The reason is obvious
because data component exists for that generation (in this scenario).
After that, user will not be able to boot scylla anymore because there is
a generation with both a TOC and a temporary TOC. We cannot simply remove a
generation with TOC and temporary TOC because user data will be lost (again,
in this scenario). After all, the temporary TOC was only created because
sstable::write_components() was wrongly called with the generation of a
sstable that exists.
Solution proposed by this patch is to trigger exception if a TOC file
exists for the generation used.
Some SSTable unit tests were also changed to guarantee that we don't try
to overwrite components of an existing sstable.
Refs #1014.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <caffc4e19cdcf25e4c6b9dd277d115422f8246c4.1457643565.git.raphaelsc@scylladb.com>
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