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From Alexey Zotov <azo...@griddynamics.com>
Subject unnecessary tombstone's transmission during repair process
Date Thu, 11 Oct 2012 15:41:51 GMT
Hi Guys,

I have a question about merkle tree construction and repair process. When
mercle tree is constructing it calculates hashes. For DeletedColumn it
calculates hash using value. Value of DeletedColumn is a serialized local
deletion time. We know that local deletion time can be different on
different nodes for the same tombstone. So hashes of the same tombstone on
different nodes will be different. Is it true? I think that local deletion
time shouldn't be considered in hash's calculation.

We've provided several tests:
// we have 3 node, RF=2, CL=QUORUM. So we have strong consistency.
1. Populate data to all nodes. Run repair process. No any streams were
transmitted. It's predictable behaviour.
2. Then we removed some columns for some rows. No any nodes we down. All
writes were done successfully. We run repair. There were some streams. It's
strange for me, because all data should be consistent.

We've created some patch and applied it.
1. Result of the first test is the same.
2. Result of the second test: there were no any unnecessary streams as I
expected.


My question is:
Is transmission of the equals tombstones during repair process a feature?
:) or is it a bug?
If it's a bug, I'll create ticket and attach patch to it.

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