apache/cassandra · error · InvalidRequestException

Duplicate column ' ' in index target list

Error message

Duplicate column '%s' in index target list

What it means

Thrown while applying CREATE INDEX when the prepared list of IndexTargets contains the same column more than once. The duplicate arises from the raw target list given in the statement (rawIndexTargets), and the request is rejected before any index metadata is built.

Solutions

1. Remove the duplicate column from the index target list.

When it happens

Trigger: Thrown at src/java/org/apache/cassandra/cql3/statements/schema/CreateIndexStatement.java:201 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/2a1c9658195899e9. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/cql3/statements/schema/CreateIndexStatement.java:201

                                                  ? String.format("on table %s", table.name)
                                                  : String.format("%s on table %s", indexName, table.name),
                                                  false,
                                                  state);

        List<IndexTarget> indexTargets = Lists.newArrayList(transform(rawIndexTargets, t -> t.prepare(table)));

        if (indexTargets.isEmpty() && !attrs.isCustom)
            throw ire(CUSTOM_CREATE_WITHOUT_COLUMN);

        if (indexTargets.size() > 1)
        {
            if (!attrs.isCustom)
                throw ire(CUSTOM_MULTIPLE_COLUMNS);

            Set<ColumnIdentifier> columns = new HashSet<>();
            for (IndexTarget target : indexTargets)
                if (!columns.add(target.column))
                    throw ire(DUPLICATE_TARGET_COLUMN, target.column);
        }

        IndexMetadata.Kind kind = attrs.isCustom ? IndexMetadata.Kind.CUSTOM : IndexMetadata.Kind.COMPOSITES;

        indexTargets.forEach(t -> validateIndexTarget(table, kind, t, attrs));

        String name = null == indexName ? generateIndexName(keyspace, indexTargets) : indexName;

        Map<String, String> options = attrs.isCustom ? attrs.getOptions() : Collections.emptyMap();

        IndexMetadata index = IndexMetadata.fromIndexTargets(indexTargets, name, kind, options);

        // check to disallow creation of an index which duplicates an existing one in all but name
        IndexMetadata equalIndex = tryFind(table.indexes, i -> i.equalsWithoutName(index)).orNull();
        if (null != equalIndex)
        {
            if (ifNotExists)
                return schema;

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