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From bdeggleston <...@git.apache.org>
Subject [GitHub] cassandra pull request #224: 14405 replicas
Date Wed, 16 May 2018 21:43:58 GMT
Github user bdeggleston commented on a diff in the pull request:

    https://github.com/apache/cassandra/pull/224#discussion_r188782098
  
    --- Diff: src/java/org/apache/cassandra/cql3/statements/AlterKeyspaceStatement.java ---
    @@ -96,7 +98,35 @@ private void warnIfIncreasingRF(KeyspaceMetadata ksm, KeyspaceParams
params)
                                                                                         
                   StorageService.instance.getTokenMetadata(),
                                                                                         
                   DatabaseDescriptor.getEndpointSnitch(),
                                                                                         
                   params.replication.options);
    -        if (newStrategy.getReplicationFactor() > oldStrategy.getReplicationFactor())
    +
    +        validateTransientReplication(oldStrategy, newStrategy);
    +        warnIfIncreasingRF(oldStrategy, newStrategy);
    +    }
    +
    +    private void validateTransientReplication(AbstractReplicationStrategy oldStrategy,
AbstractReplicationStrategy newStrategy)
    +    {
    +        if (oldStrategy.getReplicationFactor().trans == 0 && newStrategy.getReplicationFactor().trans
> 0)
    +        {
    +            Keyspace ks = Keyspace.open(keyspace());
    +            for (ColumnFamilyStore cfs: ks.getColumnFamilyStores())
    +            {
    +                if (cfs.viewManager.hasViews())
    +                {
    +                    throw new ConfigurationException("Cannot use transient replication
on keyspaces using materialized views");
    +                }
    +
    +                if (cfs.indexManager.hasIndexes())
    +                {
    +                    throw new ConfigurationException("Cannot use transient replication
on keyspaces using secondary indexes");
    +                }
    +            }
    +
    +        }
    +    }
    --- End diff --
    
    If you're keeping the total number of replicas the same, I don't think there would  be
any difference between reducing the number of transient replicas, and increasing the replication
factor on a normally replicated keyspace. You'd just decrease transient count one at a time
and do a full repair between each? If you were reducing both (ie: 5/2 -> 4/1), that shouldn't
cause any problems at all.


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