apache/cassandra · error · InvalidRequestException

Truncation is not supported by table %s

Error message

Truncation is not supported by table %s

What it means

AbstractLazyVirtualTable.truncate rejects TRUNCATE statements because lazily-computed virtual tables have no persisted data to remove. Throwing InvalidRequestException makes the read-only contract explicit instead of silently no-op'ing the TRUNCATE.

Source

Thrown at src/java/org/apache/cassandra/db/virtual/AbstractLazyVirtualTable.java:780

        catch (InternalTimeoutException ignore)
        {
            if (onTimeout != OnTimeout.BEST_EFFORT || collector.isEmpty())
                throw new ReadTimeoutException(ONE, 0, 1, false);
            ClientWarn.instance.warn("Ran out of time. Returning best effort.");
        }
        return collector.finish();
    }

    @Override
    public void apply(PartitionUpdate update)
    {
        throw new InvalidRequestException("Modification is not supported by table " + metadata);
    }

    @Override
    public void truncate()
    {
        throw new InvalidRequestException("Truncation is not supported by table " + metadata);
    }

    @Override
    public String toString()
    {
        return metadata().toString();
    }

    static Object[] composePartitionKeys(DecoratedKey decoratedKey, TableMetadata metadata)
    {
        if (metadata.partitionKeyColumns().size() == 1)
            return new Object[] { metadata.partitionKeyType.compose(decoratedKey.getKey()) };

        ByteBuffer[] split = ((CompositeType)metadata.partitionKeyType).split(decoratedKey.getKey());
        Object[] result = new Object[split.length];
        for (int i = 0 ; i < split.length ; ++i)
            result[i] = metadata.partitionKeyColumns().get(i).type.compose(split[i]);
        return result;

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Remove TRUNCATE of virtual tables from scripts/harnesses — their contents are derived from live JVM state
2. Reset the underlying runtime state via nodetool or configuration instead
3. If the table is truly mutable, it must be an AbstractMutableLazyVirtualTable-backed table; verify which implementation backs the target table

Example fix

// before
TRUNCATE system_views.threads;
// after
// virtual tables cannot be truncated; skip tables where
// metadata().isVirtual() is true in cleanup code

if (metadata.isVirtual()) throw new UnsupportedOperationException("cannot truncate virtual table");

try { session.execute("TRUNCATE " + table); } catch (InvalidRequestException e) { if (e.getMessage().startsWith("Truncation is not supported")) skipTable(table); else throw e; }

When it happens

Trigger: Running `TRUNCATE <virtual_table>` on any read-only virtual table, e.g. `TRUNCATE system_views.threads` or `TRUNCATE system.local`.

Common situations: Cleanup scripts that truncate staging/test tables applied blindly to system_views; test harnesses resetting table contents without excluding virtual tables.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Modification is not supported by table %s
• Cannot TRUNCATE materialized view directly; must truncate ba
• Operator %s not supported for txn_id
• %s does not support complex column updates
• Unknown keyspace: '" + keyspaceName + "'

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/3db622b4a4311ac5. Report an issue: GitHub.