apache/cassandra · error · InvalidRequestException

Invalid consistency for conditional update. Must be one of S

Error message

Invalid consistency for conditional update. Must be one of SERIAL or LOCAL_SERIAL

What it means

validateForCas ensures the serial consistency used for a lightweight transaction is one of SERIAL or LOCAL_SERIAL. Any other level passed as the serial consistency of a conditional update is rejected, because Paxos phases only support these two serial modes.

Source

Thrown at src/java/org/apache/cassandra/db/ConsistencyLevel.java:260

    public void validateForCasCommit(AbstractReplicationStrategy replicationStrategy) throws InvalidRequestException
    {
        switch (this)
        {
            case EACH_QUORUM:
                requireNetworkTopologyStrategy(replicationStrategy);
                break;
            case SERIAL:
            case UNSAFE_DELAY_SERIAL:
            case LOCAL_SERIAL:
            case UNSAFE_DELAY_LOCAL_SERIAL:
                throw new InvalidRequestException(this + " is not supported as conditional update commit consistency. Use ANY if you mean \"make sure it is accepted but I don't care how many replicas commit it for non-SERIAL reads\"");
        }
    }

    public void validateForCas() throws InvalidRequestException
    {
        if (!isSerialConsistency())
            throw new InvalidRequestException("Invalid consistency for conditional update. Must be one of SERIAL or LOCAL_SERIAL");
    }

    public boolean isSerialConsistency()
    {
        switch (this)
        {
            case SERIAL:
            case UNSAFE_DELAY_SERIAL:
            case LOCAL_SERIAL:
            case UNSAFE_DELAY_LOCAL_SERIAL:
                return true;
            default:
                return false;
        }
    }

    public void validateCounterForWrite(TableMetadata metadata) throws InvalidRequestException
    {

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Set the serial consistency to ConsistencyLevel.SERIAL (default) or LOCAL_SERIAL.
2. Keep regular (commit) consistency separate; only the serial slot is validated here.
3. Audit code that copies one consistency enum into both consistency and serial-consistency parameters.
4. In cqlsh use `SERIAL CONSISTENCY LOCAL_SERIAL;` with only those two values.

Example fix

// before
stmt.setSerialConsistencyLevel(ConsistencyLevel.QUORUM);
// after
stmt.setSerialConsistencyLevel(ConsistencyLevel.LOCAL_SERIAL);

// Guard serial CL before LWT execution
if (serialCl != ConsistencyLevel.SERIAL && serialCl != ConsistencyLevel.LOCAL_SERIAL)
    throw new IllegalArgumentException("serial CL must be SERIAL or LOCAL_SERIAL");

catch (InvalidRequestException e) {
    if (e.getMessage().contains("Invalid consistency for conditional update")) {
        statement.setSerialConsistencyLevel(ConsistencyLevel.SERIAL);
        retry();
    } else throw e;
}

When it happens

Trigger: Calling execute with a conditional update whose serial consistency is set to something like QUORUM, ONE, or SERIAL-derived UNSAFE variants not accepted, e.g. stmt.setSerialConsistencyLevel(ConsistencyLevel.QUORUM).

Common situations: Application-wide consistency settings accidentally applied to the serial consistency slot; old drivers exposing serial consistency incorrectly; copy-pasted consistency configuration.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• this + " is not supported as conditional update commit consi
• ANY ConsistencyLevel is only supported for writes
• You must use conditional updates for serializable writes
• Consistency level ANY is not yet supported for counter table
• Counter operations are inherently non-serializable

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/198787ace89c4c96. Report an issue: GitHub.