apache/seatunnel · error · IllegalArgumentException

Cannot build a NebulaGraph request for an empty batch.

Error message

Cannot build a NebulaGraph request for an empty batch.

What it means

NebulaGraphStatementBuilder.build() requires a non-empty list of vertices because it constructs an nGQL INSERT/UPDATE statement from them; an empty list would produce syntactically invalid nGQL, so it throws IllegalArgumentException immediately. This is an internal invariant check on batch construction.

Solutions

Skip building/sending the request when the vertex list is empty: only call build() if !vertices.isEmpty()
Check upstream transform logic if batches are unexpectedly empty on flush
If calling the builder from custom code, add a size check before invocation

Example fix

// before
NebulaGraphWriteRequest req = builder.build(vertices);
// after
if (!vertices.isEmpty()) {
    NebulaGraphWriteRequest req = builder.build(vertices);
}

Defensive patterns

Strategy: validation

Validate before calling

if (vertices == null || vertices.isEmpty()) { return; } // skip build/flush

Try / catch

try { req = builder.build(vertices); } catch (IllegalArgumentException e) { if (e.getMessage().contains("empty batch")) { req = null; } else { throw e; } }

Prevention

Check batch size before building requests
Only flush when the buffer has accumulated rows
Guard upstream filters that may remove all rows

When it happens

Trigger: Calling build(List.of()) directly (as in tests) or via request() when the accumulated batch of NebulaGraphVertex is empty — e.g. flush triggered with nothing buffered.

Common situations: Empty upstream data leading to a zero-row batch flush; filter transforms removing all rows before the sink; unit tests probing boundary behavior of the statement builder.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/c79c67e0a08a0d3c. Report an issue: GitHub.

Appendix: source

Thrown at seatunnel-connectors-v2/connector-nebulagraph/src/main/java/org/apache/seatunnel/connectors/seatunnel/nebulagraph/sink/NebulaGraphStatementBuilder.java:51

    private static final Pattern IDENTIFIER = Pattern.compile("[A-Za-z_][A-Za-z0-9_]*");

    private final String quotedTag;
    private final List<String> propertyNames;
    private final NebulaGraphWriteMode writeMode;

    NebulaGraphStatementBuilder(
            String tag, List<String> propertyNames, NebulaGraphWriteMode writeMode) {
        this.quotedTag = quoteIdentifier(tag);
        this.propertyNames =
                propertyNames.stream()
                        .map(NebulaGraphStatementBuilder::validateIdentifier)
                        .collect(Collectors.toList());
        this.writeMode = writeMode;
    }

    NebulaGraphWriteRequest build(List<NebulaGraphVertex> vertices) {
        if (vertices.isEmpty()) {
            throw new IllegalArgumentException(
                    "Cannot build a NebulaGraph request for an empty batch.");
        }
        if (writeMode == NebulaGraphWriteMode.INSERT) {
            return buildInsert(vertices);
        }
        return buildUpdate(vertices);
    }

    private NebulaGraphWriteRequest buildInsert(List<NebulaGraphVertex> vertices) {
        Map<String, Object> parameters = new LinkedHashMap<>();
        List<String> values = new ArrayList<>(vertices.size());
        for (int row = 0; row < vertices.size(); row++) {
            NebulaGraphVertex vertex = vertices.get(row);

            List<String> propertyParameters = new ArrayList<>(propertyNames.size());
            for (int field = 0; field < propertyNames.size(); field++) {
                String parameter = parameterName(row, field);
                parameters.put(parameter, vertex.getProperties().get(propertyNames.get(field)));

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