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From "amorton (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-11050) SSTables not loaded after dropping column
Date Wed, 20 Jan 2016 22:22:40 GMT
amorton created CASSANDRA-11050:
-----------------------------------

             Summary: SSTables not loaded after dropping column
                 Key: CASSANDRA-11050
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11050
             Project: Cassandra
          Issue Type: Bug
            Reporter: amorton
            Assignee: amorton


The {{system_schema.dropped_tables}} table is not flushed when schema is updated, this can
result in SSTables not being loaded at startup and failure to start if the commit log contains
mutations with the column. 

Reproduce on cassandra-3.0 branch by starting a node and running following in cqlsh:

{code}
create keyspace dev WITH replication = {'class':'SimpleStrategy', 'replication_factor':1};

use dev;

create table foo (
     foo text primary key,
     bar text,
     baz text
);

insert into foo (foo, bar, baz) values ('foo','this is bar', 'this is baz');

alter table foo 
drop baz;
{code}

Stop the node and restart, the following errors are raised and the node does not start:

{code}
ERROR 16:38:19 Exception in thread Thread[SSTableBatchOpen:1,5,main]
java.lang.RuntimeException: Unknown column baz during deserialization
	at org.apache.cassandra.db.SerializationHeader$Component.toHeader(SerializationHeader.java:331)
~[main/:na]
	at org.apache.cassandra.io.sstable.format.SSTableReader.open(SSTableReader.java:485) ~[main/:na]
	at org.apache.cassandra.io.sstable.format.SSTableReader.open(SSTableReader.java:374) ~[main/:na]
	at org.apache.cassandra.io.sstable.format.SSTableReader$4.run(SSTableReader.java:533) ~[main/:na]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[na:1.8.0_60]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_60]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) ~[na:1.8.0_60]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_60]
	at java.lang.Thread.run(Thread.java:745) [na:1.8.0_60]
...
ERROR 16:38:19 Exiting due to error while processing commit log during initialization.
org.apache.cassandra.db.commitlog.CommitLogReplayer$CommitLogReplayException: Unexpected error
deserializing mutation; saved to /var/folders/r2/rkv1jz3j0j74r9s1zm5xx9wc0000gn/T/mutation5408885979635225676dat.
 This may be caused by replaying a mutation against a table with the same name but incompatible
schema.  Exception follows: java.lang.RuntimeException: Unknown column baz during deserialization
	at org.apache.cassandra.db.commitlog.CommitLogReplayer.handleReplayError(CommitLogReplayer.java:633)
[main/:na]
	at org.apache.cassandra.db.commitlog.CommitLogReplayer.replayMutation(CommitLogReplayer.java:556)
[main/:na]
	at org.apache.cassandra.db.commitlog.CommitLogReplayer.replaySyncSection(CommitLogReplayer.java:509)
[main/:na]
	at org.apache.cassandra.db.commitlog.CommitLogReplayer.recover(CommitLogReplayer.java:404)
[main/:na]
	at org.apache.cassandra.db.commitlog.CommitLogReplayer.recover(CommitLogReplayer.java:151)
[main/:na]
	at org.apache.cassandra.db.commitlog.CommitLog.recover(CommitLog.java:189) [main/:na]
	at org.apache.cassandra.db.commitlog.CommitLog.recover(CommitLog.java:169) [main/:na]
	at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:283) [main/:na]
	at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:551) [main/:na]
	at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:679) [main/:na]
{code}

{{dropped_columns}} is not in the list of tables to flush, {{SchemaKeyspace.ALL}}. 

It's a simple patch to add it, attached. The fix will need to go to 3.0, 3.1 and trunk AFAIK

however this will change the way the schema hash is calculated in {{SchemaKeyspace.calculateSchemaDigest()}}
It looks like this would cause the nodes to announce a new version of the schema on (first)
restart. 

I  currently donit understand all the implications of changing the schema hash, thoughts ?




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