apache/flink · error · IllegalArgumentException

Cannot use the key partitioner for composite keys (more than

Error message

Cannot use the key partitioner for composite keys (more than one key field)

What it means

Error "Cannot use the key partitioner for composite keys (more than one key field)" thrown in apache/flink.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/operators/base/PartitionOperatorBase.java:111

    }

    public Ordering getOrdering() {
        return ordering;
    }

    public void setDistribution(DataDistribution distribution) {
        this.distribution = distribution;
    }

    public void setCustomPartitioner(Partitioner<?> customPartitioner) {
        if (customPartitioner != null) {
            int[] keys = getKeyColumns(0);
            if (keys == null || keys.length == 0) {
                throw new IllegalArgumentException(
                        "Cannot use custom partitioner for a non-grouped GroupReduce (AllGroupReduce)");
            }
            if (keys.length > 1) {
                throw new IllegalArgumentException(
                        "Cannot use the key partitioner for composite keys (more than one key field)");
            }
        }
        this.customPartitioner = customPartitioner;
    }

    @Override
    public SingleInputSemanticProperties getSemanticProperties() {
        return new SingleInputSemanticProperties.AllFieldsForwardedProperties();
    }

    // --------------------------------------------------------------------------------------------

    @Override
    protected List<IN> executeOnCollections(
            List<IN> inputData, RuntimeContext runtimeContext, ExecutionConfig executionConfig) {
        return inputData;
    }

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Address the cause reported by the error message: Cannot use the key partitioner for composite keys (more than one key field)
2. Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry.

Example fix

Correct the condition described ("Cannot use the key partitioner for composite keys (more than one key field)") and rerun the job or command.

When it happens

Trigger: Triggered at runtime when the operation fails because: Cannot use the key partitioner for composite keys (more than one key field).

Common situations: Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: Cannot use the key partitioner for composite keys (more than one key field).

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/b1f1aa521f7a3367. Report an issue: GitHub.