[jira] [Created] (CASSANDRA-15926) When schema does not match sstable serialization header compaction may fail

[David Capwell (Jira)]

David Capwell created CASSANDRA-15926:
-----------------------------------------

             Summary: When schema does not match sstable serialization header 
compaction may fail
                 Key: CASSANDRA-15926
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15926
             Project: Cassandra
          Issue Type: Improvement
          Components: Cluster/Schema, Local/SSTable
            Reporter: David Capwell


If the table schema had timeuuid and then an alter is done to change the column 
to uuid, then the on-disk serialization header won’t match the table schema; 
this is problematic as there isn’t logic to migrate the column from the old 
type to the new type.

The ALTER TABLE command does not directly allow this type of schema change 
(though possible before 3.0.11, see CASSANDRA-12443), but this is possible if 
the following is done

{code}
INSERT INTO system_schema.columns (keyspace_name, table_name, column_name, 
clustering_order, column_name_bytes, kind, position, type) VALUES (‘ks', 
’table', ‘col', 'none', bytes, 'regular', -1, 'uuid’);
ALTER TABLE ks.table WITH comment = 'something’; — this will trigger the schema 
to migrate across the cluster
{code}

The below is a test to show this

{code}
package org.apache.cassandra.distributed.test;

import java.util.UUID;

import org.junit.Test;

import org.apache.cassandra.distributed.Cluster;
import org.apache.cassandra.distributed.impl.IInvokableInstance;
import org.apache.cassandra.utils.UUIDGen;

public class AlterWithOnDiskMismatch extends DistributedTestBase
{
    @Test
    public void alterTypeMixedSSTablesNoConflict() throws Throwable
    {
        try (Cluster cluster = init(Cluster.create(1)))
        {
            IInvokableInstance node = cluster.get(1);

            cluster.schemaChange("CREATE TABLE " + KEYSPACE + ".mismatch (key 
text primary key, value timeuuid)");

            // write valid timeuuid then flush
            node.executeInternal("INSERT INTO " + KEYSPACE + ".mismatch (key, 
value) VALUES (?, ?)", "k1", UUIDGen.getTimeUUID());
            node.flush(KEYSPACE);

            // alter schema
            Object[] columns = node.executeInternal("SELECT keyspace_name, 
table_name, column_name, clustering_order, column_name_bytes, kind, position, 
type " +
                                 "FROM system_schema.columns WHERE 
keyspace_name=? AND table_name=? AND column_name=?", KEYSPACE, "mismatch", 
"value")[0];

            columns[columns.length - 1] = "uuid";
            node.executeInternal("INSERT INTO system_schema.columns 
(keyspace_name, table_name, column_name, clustering_order, column_name_bytes, 
kind, position, type) VALUES (?, ?, ?, ?, ?, ?, ?, ?)", columns);
            cluster.schemaChange("ALTER TABLE " + KEYSPACE + ".mismatch WITH 
comment='upgrade'");

            node.executeInternal("INSERT INTO " + KEYSPACE + ".mismatch (key, 
value) VALUES (?, ?)", "k2", UUID.randomUUID());
            node.flush(KEYSPACE);

            node.forceCompact(KEYSPACE, "mismatch");
        }
    }

    @Test
    public void alterTypeMixedSSTablesConflict() throws Throwable
    {
        try (Cluster cluster = init(Cluster.create(1)))
        {
            IInvokableInstance node = cluster.get(1);

            cluster.schemaChange("CREATE TABLE " + KEYSPACE + ".mismatch (key 
text primary key, value timeuuid)");

            // write valid timeuuid then flush
            node.executeInternal("INSERT INTO " + KEYSPACE + ".mismatch (key, 
value) VALUES (?, ?)", "k1", UUIDGen.getTimeUUID());
            node.flush(KEYSPACE);

            // alter schema
            Object[] columns = node.executeInternal("SELECT keyspace_name, 
table_name, column_name, clustering_order, column_name_bytes, kind, position, 
type " +
                                                    "FROM system_schema.columns 
WHERE keyspace_name=? AND table_name=? AND column_name=?", KEYSPACE, 
"mismatch", "value")[0];

            columns[columns.length - 1] = "uuid";
            node.executeInternal("INSERT INTO system_schema.columns 
(keyspace_name, table_name, column_name, clustering_order, column_name_bytes, 
kind, position, type) VALUES (?, ?, ?, ?, ?, ?, ?, ?)", columns);
            cluster.schemaChange("ALTER TABLE " + KEYSPACE + ".mismatch WITH 
comment='upgrade'");

            node.executeInternal("INSERT INTO " + KEYSPACE + ".mismatch (key, 
value) VALUES (?, ?)", "k1", UUID.randomUUID());
            node.flush(KEYSPACE);

            node.forceCompact(KEYSPACE, "mismatch");
        }
    }
}
{code}



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