What causes "Csv file does not support this compress type: {}" in apache/seatunnel?

Change the compress option to a CSV-supported format such as gzip or none

Csv file does not support this compress type

Error message

Csv file does not support this compress type: {}

What it means

This warning is emitted by CsvWriteStrategy.getOrCreateOutputStream when the configured compress format is not one of the branches explicitly handled for CSV output. The strategy logs a warning and falls back to an uncompressed stream, still writing the CSV header. The output file therefore will NOT be compressed as the user requested.

Solutions

Change the compress option to a CSV-supported format such as gzip or none
Verify supported compress values in the file connector docs for csv format
Switch file_format to ORC/Parquet if columnar compression codecs are required
Patch CsvWriteStrategy.getOrCreateOutputStream to add the missing codec case if it must be supported

Example fix

// before
sink = {
  file_format = "csv"
  compress = "snappy"
}
// after
sink = {
  file_format = "csv"
  compress = "gzip"
}

Defensive patterns

Strategy: validation

Validate before calling

// verify the compress option before building the CSV sink
List<String> csvSupported = List.of("none", "lzo", "gzip");
if (!csvSupported.contains(compressValue.toLowerCase())) {
    throw new IllegalArgumentException("CSV sink supports only " + csvSupported + ", got: " + compressValue);
}

Prevention

Cross-check compress option against the csv file-format docs
Validate sink configs in CI with a dry-run/local job
Inspect output file extensions after test writes to confirm compression applied
Add unit tests asserting each CompressFormat is either handled or rejected

When it happens

Trigger: A CSV file sink configured with a compress codec lacking a case in the switch (e.g. ZSTD/BROTLI); getOrCreateOutputStream runs on first write to a new file, hits the default branch and logs this warning.

Common situations: Reusing a shared sink config across file formats; assuming CSV supports all Hadoop codecs; enum additions in CompressFormat not propagated to CsvWriteStrategy.

Related errors

AI-assisted analysis of apache/seatunnel@cf67b549a7 (2026-09-10). Data as JSON: /api/errors/f785c5c87b281fda. Report an issue: GitHub.

Appendix: source

Thrown at seatunnel-connectors-v2/connector-file/connector-file-base/src/main/java/org/apache/seatunnel/connectors/seatunnel/file/sink/writer/CsvWriteStrategy.java:169

    public FSDataOutputStream getOrCreateOutputStream(@NonNull String filePath) {
        FSDataOutputStream fsDataOutputStream = beingWrittenOutputStream.get(filePath);
        if (fsDataOutputStream == null) {
            try {
                switch (compressFormat) {
                    case LZO:
                        LzopCodec lzo = new LzopCodec();
                        OutputStream out =
                                lzo.createOutputStream(
                                        hadoopFileSystemProxy.getOutputStream(filePath));
                        fsDataOutputStream = new FSDataOutputStream(out, null);
                        enableWriteHeader(fsDataOutputStream);
                        break;
                    case NONE:
                        fsDataOutputStream = hadoopFileSystemProxy.getOutputStream(filePath);
                        enableWriteHeader(fsDataOutputStream);
                        break;
                    default:
                        log.warn(
                                "Csv file does not support this compress type: {}",
                                compressFormat.getCompressCodec());
                        fsDataOutputStream = hadoopFileSystemProxy.getOutputStream(filePath);
                        enableWriteHeader(fsDataOutputStream);
                        break;
                }
                beingWrittenOutputStream.put(filePath, fsDataOutputStream);
                isFirstWrite.put(filePath, true);
            } catch (IOException e) {
                throw CommonError.fileOperationFailed("CsvFile", "open", filePath, e);
            }
        }
        return fsDataOutputStream;
    }

    private void enableWriteHeader(FSDataOutputStream fsDataOutputStream) throws IOException {
        if (enableHeaderWriter) {
            fsDataOutputStream.write(String.join(",", seaTunnelRowType.getFieldNames()).getBytes());

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