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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-2590) row delete breaks read repair
Date Tue, 03 May 2011 22:03:03 GMT


Jonathan Ellis updated CASSANDRA-2590:

    Attachment: 2590-v2.txt

... but that's not what we want for RowRepairResolver. (I freely admit that dealing with tombstones
is subtle and tricky. :)

removeDeleted will give you back a version of the row with any GC-able tombstones removed.
That's not what we want for read repair; we want to preserve tombstones, but we want a "canonical"
representation of only the minimum tombstones necessary.

Instead we want to do what you were doing with ensureRelevant, and drop columns that are irrelevant.
But it's a little more complex than that because we have the same problem at the supercolumn
level, as at the row level.

Here's a patch that uses an IdentityQueryFilter to run through the isRelevant logic using
the same supercolumn-aware code that we use when merging versions from different memtables/sstables.

> row delete breaks read repair 
> ------------------------------
>                 Key: CASSANDRA-2590
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 0.7.5, 0.8 beta 1
>            Reporter: Aaron Morton
>            Assignee: Aaron Morton
>            Priority: Minor
>         Attachments: 0001-cf-resolve-test-and-possible-solution-for-read-repai.patch,
> related to CASSANDRA-2589 
> Working at CL ALL can get inconsistent reads after row deletion. Reproduced on the 0.7
and 0.8 source. 
> Steps to reproduce:
> # two node cluster with rf 2 and HH turned off
> # insert rows via cli 
> # flush both nodes 
> # shutdown node 1
> # connect to node 2 via cli and delete one row
> # bring up node 1
> # connect to node 1 via cli and issue get with CL ALL 
> # first get returns the deleted row, second get returns zero rows.
> RowRepairResolver.resolveSuperSet() resolves a local CF with the old row columns, and
the remote CF which is marked for deletion. CF.resolve() does not pay attention to the deletion
flags and the resolved CF has both markedForDeletion set and a column with a lower timestamp.
The return from resolveSuperSet() is used as the return for the read without checking if the
cols are relevant. 
> Also when RowRepairResolver.mabeScheduleRepairs() runs it sends two mutations. Node 1
is given the row level deletation, and Node 2 is given a mutation to write the old (and now
deleted) column from node 2. I have some log traces for this if needed. 
> A quick fix is to check for relevant columns in the RowRepairResolver, will attach shortly.

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