apache/cassandra · error · ConfigurationException

SetType takes exactly 1 type parameter

Error message

SetType takes exactly 1 type parameter

What it means

SetType.getInstance(TypeParser) constructs a SetType from parsed type parameters, e.g. set<element_type>. It throws ConfigurationException when the parser does not provide exactly one type parameter, because a set needs exactly one element type.

Source

Thrown at src/java/org/apache/cassandra/db/marshal/SetType.java:61

import org.apache.cassandra.utils.JsonUtils;
import org.apache.cassandra.utils.bytecomparable.ByteComparable;
import org.apache.cassandra.utils.bytecomparable.ByteSource;

public class SetType<T> extends CollectionType<Set<T>>
{
    // interning instances
    private static final ConcurrentHashMap<AbstractType<?>, SetType> instances = new ConcurrentHashMap<>();
    private static final ConcurrentHashMap<AbstractType<?>, SetType> frozenInstances = new ConcurrentHashMap<>();

    private final AbstractType<T> elements;
    private final SetSerializer<T> serializer;
    private final boolean isMultiCell;

    public static SetType<?> getInstance(TypeParser parser) throws ConfigurationException, SyntaxException
    {
        List<AbstractType<?>> l = parser.getTypeParameters();
        if (l.size() != 1)
            throw new ConfigurationException("SetType takes exactly 1 type parameter");

        return getInstance(l.get(0).freeze(), true);
    }

    public static <T> SetType<T> getInstance(AbstractType<T> elements, boolean isMultiCell)
    {
        ConcurrentHashMap<AbstractType<?>, SetType> internMap = isMultiCell ? instances : frozenInstances;
        SetType<T> t = internMap.get(elements);
        return null == t
             ? internMap.computeIfAbsent(elements, k -> new SetType<>(k, isMultiCell))
             : t;
    }

    public SetType(AbstractType<T> elements, boolean isMultiCell)
    {
        super(ComparisonType.CUSTOM, Kind.SET);
        this.elements = elements;
        this.serializer = SetSerializer.getInstance(elements.getSerializer(), elements.comparatorSet);

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Supply exactly one element type: e.g. set<org.apache.cassandra.db.marshal.Int32Type>.
2. If two element types were intended, use map<k,v> instead of set.
3. Catch ConfigurationException around TypeParser.parse()/getInstance and validate the type string before use.

Example fix

// before
TypeParser.parse("SetType(Int32Type, UTF8Type)");
// after
TypeParser.parse("SetType(Int32Type)");

List<AbstractType<?>> params = parser.getTypeParameters();
if (params.size() != 1)
    throw new ConfigurationException("set type requires exactly 1 parameter, got " + params.size());

try {
    SetType<?> st = SetType.getInstance(parser);
} catch (ConfigurationException e) {
    // report malformed set type definition
} catch (SyntaxException e) {
    // report unparseable type string
}

When it happens

Trigger: Parsing a type string like 'org.apache.cassandra.db.marshal.SetType' with zero parameters or with two or more parameters (e.g. set<int, text>) into SetType.getInstance(parser).

Common situations: Malformed schema definitions with extra type arguments; confusing set with map syntax (map takes 2 parameters, set takes 1); programmatic type parsing of user-supplied strings.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

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• JAAS login configuration missing for JMX authenticator setup

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/3e06087e4035f14d. Report an issue: GitHub.