apache/flink · error · RuntimeException

Type information for left input of type {} is not supported.

Error message

Type information for left input of type {} is not supported. Could not generate a comparator.

What it means

Error "Type information for left input of type {} is not supported. Could not generate a comparator." thrown in apache/flink.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/operators/base/InnerJoinOperatorBase.java:120

        TypeSerializer<IN2> rightSerializer =
                rightInformation.createSerializer(executionConfig.getSerializerConfig());

        TypeComparator<IN1> leftComparator;
        TypeComparator<IN2> rightComparator;

        if (leftInformation instanceof AtomicType) {
            leftComparator =
                    ((AtomicType<IN1>) leftInformation).createComparator(true, executionConfig);
        } else if (leftInformation instanceof CompositeType) {
            int[] keyPositions = getKeyColumns(0);
            boolean[] orders = new boolean[keyPositions.length];
            Arrays.fill(orders, true);

            leftComparator =
                    ((CompositeType<IN1>) leftInformation)
                            .createComparator(keyPositions, orders, 0, executionConfig);
        } else {
            throw new RuntimeException(
                    "Type information for left input of type "
                            + leftInformation.getClass().getCanonicalName()
                            + " is not supported. Could not generate a comparator.");
        }

        if (rightInformation instanceof AtomicType) {
            rightComparator =
                    ((AtomicType<IN2>) rightInformation).createComparator(true, executionConfig);
        } else if (rightInformation instanceof CompositeType) {
            int[] keyPositions = getKeyColumns(1);
            boolean[] orders = new boolean[keyPositions.length];
            Arrays.fill(orders, true);

            rightComparator =
                    ((CompositeType<IN2>) rightInformation)
                            .createComparator(keyPositions, orders, 0, executionConfig);
        } else {
            throw new RuntimeException(

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Address the cause reported by the error message: Type information for left input of type the reported value is not supported. Could not generate a comparator.
2. Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry.

Example fix

Correct the condition described ("Type information for left input of type the reported value is not supported. Could not generate a comparator.") and rerun the job or command.

When it happens

Trigger: Triggered at runtime when the operation fails because: Type information for left input of type the reported value is not supported. Could not generate a comparator.

Common situations: Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: Type information for left input of type the reported value is not supported. Could not generate a comparator.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/640188a6e11628e3. Report an issue: GitHub.