apache/cassandra · error · IllegalArgumentException

CAS is supported only for type 'samerow'

Error message

CAS is supported only for type 'samerow'

What it means

CASQuery performs lightweight-transaction (Compare-And-Set) operations, which cassandra-stress only supports when arguments are selected with the 'samerow' ArgSelect (all values taken from the same row). If a CAS statement is configured with 'multirow' or another arg-select type, the constructor throws IllegalArgumentException.

Source

Thrown at tools/stress/src/org/apache/cassandra/stress/operations/userdefined/CASQuery.java:71

import org.apache.cassandra.stress.report.Timer;
import org.apache.cassandra.stress.settings.StressSettings;
import org.apache.cassandra.stress.util.JavaDriverClient;

public class CASQuery extends SchemaStatement
{
    private final ImmutableList<Integer> keysIndex;
    private final ImmutableMap<Integer, Integer> casConditionArgFreqMap;
    private final String readQuery;

    private PreparedStatement casReadConditionStatement;

    public CASQuery(Timer timer, StressSettings settings, PartitionGenerator generator, SeedManager seedManager, PreparedStatement statement, ConsistencyLevel cl, ArgSelect argSelect, final String tableName)
    {
        super(timer, settings, new DataSpec(generator, seedManager, new DistributionFixed(1), settings.insert.rowPopulationRatio.get(), argSelect == SchemaStatement.ArgSelect.MULTIROW ? statement.getVariables().size() : 1), statement,
              statement.getVariables().asList().stream().map(ColumnDefinitions.Definition::getName).collect(Collectors.toList()), cl);

        if (argSelect != SchemaStatement.ArgSelect.SAMEROW)
            throw new IllegalArgumentException("CAS is supported only for type 'samerow'");

        ModificationStatement.Parsed modificationStatement;
        try
        {
            modificationStatement = CQLFragmentParser.parseAnyUnhandled(CqlParser::updateStatement,
                    statement.getQueryString());
        }
        catch (RecognitionException e)
        {
            throw new IllegalArgumentException("could not parse update query:" + statement.getQueryString(), e);
        }

        final List<ColumnCondition.Raw> casConditionList = modificationStatement.getConditions();
        List<Integer> casConditionIndex = new ArrayList<>();

        boolean first = true;
        StringBuilder casReadConditionQuery = new StringBuilder();
        casReadConditionQuery.append("SELECT ");

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Set the operation's arg select type to 'samerow' in the stress profile, e.g. ops= CAS(type=samerow)
2. Remove or rewrite the CAS operation if multirow semantics are needed, since LWT on multiple rows is not supported by stress

Example fix

// before
ops: CAS(type=multirow)
// after
ops: CAS(type=samerow)

if (argSelect != SchemaStatement.ArgSelect.SAMEROW)
    throw new IllegalArgumentException("CAS requires argSelect=samerow");

boolean isCasCompatible(SchemaStatement.ArgSelect sel) { return sel == SchemaStatement.ArgSelect.SAMEROW; }

try { new CASQuery(timer, settings, gen, seeds, stmt, cl, argSelect, table); } catch (IllegalArgumentException e) { log.error("Set type=samerow for CAS in profile"); }

When it happens

Trigger: Executing a user-defined stress profile CAS operation whose statement arguments are specified with type='multirow' (or any ArgSelect other than SAMEROW) in the profile's ops spec.

Common situations: Copy-editing a stress profile YAML and changing the arg select type for an UPDATE ... IF condition; using generic multirow argument selection for an LWT operation.

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

• Username provided but no password
• Malformed target host: ${s}
• You need to state at least one --target host to replay the q
• sample range is invalid
• Invalid lookback distribution; max value is ${maxValue}, but

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/4b154ee79463acca. Report an issue: GitHub.