apache/cassandra · error · SyntaxException

is not a collection type

Error message

%s is not a collection type

What it means

Inside TypeParser.getCollectionsParameters() (used to parse DynamicCompositeType-style hex-keyed collection arguments), each parsed type must be a CollectionType (map, set, or list). This SyntaxException is thrown when a value type resolves to a non-collection AbstractType, e.g. a plain comparator like UTF8Type or Int32Type.

Solutions

1. Use a collection type after the colon, e.g. MapType.getInstance(TypeParser) form: replace UTF8Type with ListType(UTF8Type), SetType(Int32Type) or MapType(UTF8Type, Int32Type)
2. Check the message's leading type name to see which non-collection type was rejected and why it appeared
3. Verify the intent: if the field is not meant to hold collections, don't use getCollectionsParameters/DynamicCompositeType at all — use CompositeType
4. Consult the schema docs for DynamicCompositeType: every aliased value must be a collection type

Example fix

// before
TypeParser.parse("DynamicCompositeType(a => Int32Type)");
// after
TypeParser.parse("DynamicCompositeType(a => ListType(Int32Type))");

static boolean valuesAreCollectionTypes(Collection<AbstractType<?>> types) {
    return types.stream().allMatch(t -> t instanceof CollectionType);
}

static boolean isCollectionType(AbstractType<?> t) {
    return t instanceof CollectionType; // MapType, SetType, ListType
}

try {
    AbstractType<?> t = TypeParser.parse(dynamicCompositeString);
} catch (SyntaxException e) {
    if (e.getMessage().contains("is not a collection type"))
        throw new SchemaConfigurationException("DynamicCompositeType values must be map/set/list types", e);
    throw e;
}

When it happens

Trigger: Parsing a collections parameter string where a value after '<hexkey>:' parses to a non-collection type, e.g. a parameter string like "(6b6579:UTF8Type)" passed through getCollectionsParameters() — only map/set/list types are accepted after the colon.

Common situations: Developers defining DynamicCompositeType parameters who supply a scalar comparator where only ListType/SetType/MapType is allowed, copy-pasting comparator names between type families, or constructing the parameter map programmatically with the wrong AbstractType subclass.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• FrozenType() only accepts one parameter
• Invalid comparator class
• MapType takes exactly 2 type parameters
• ReversedType takes exactly one argument, " + types.size() +…
• is reserved for internal functionality

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/969653d491603add. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/marshal/TypeParser.java:381

            if (str.charAt(idx) == ')')
            {
                ++idx;
                return map;
            }

            ByteBuffer bb = fromHex(readNextIdentifier());

            skipBlank();
            if (str.charAt(idx) != ':')
                throwSyntaxError("expecting ':' token");

            ++idx;
            skipBlank();
            try
            {
                AbstractType<?> type = parse();
                if (!(type instanceof CollectionType))
                    throw new SyntaxException(type + " is not a collection type");
                map.put(bb, (CollectionType)type);
            }
            catch (SyntaxException e)
            {
                SyntaxException ex = new SyntaxException(String.format("Exception while parsing '%s' around char %d", str, idx));
                ex.initCause(e);
                throw ex;
            }
        }
        throw new SyntaxException(String.format("Syntax error parsing '%s' at char %d: unexpected end of string", str, idx));
    }

    private ByteBuffer fromHex(String hex) throws SyntaxException
    {
        try
        {
            return ByteBufferUtil.hexToBytes(hex);
        }

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