alibaba/DataX · error · RuntimeException

dx_filter paras must be 3

Error message

dx_filter paras must be 3

What it means

The dx_filter transformer requires exactly 3 parameters; a different count throws RuntimeException('dx_filter paras must be 3'), rewrapped as TRANSFORMER_ILLEGAL_PARAMETER. Expected paras: columnIndex (Integer), comparison code (like/>/</=/==/!=/>=/<=), and the comparison value string.

Source

Thrown at core/src/main/java/com/alibaba/datax/core/transport/transformer/FilterTransformer.java:28

/**
 * no comments.
 * Created by liqiang on 16/3/4.
 */
public class FilterTransformer extends Transformer {
    public FilterTransformer() {
        setTransformerName("dx_filter");
    }

    @Override
    public Record evaluate(Record record, Object... paras) {

        int columnIndex;
        String code;
        String value;

        try {
            if (paras.length != 3) {
                throw new RuntimeException("dx_filter paras must be 3");
            }

            columnIndex = (Integer) paras[0];
            code = (String) paras[1];
            value = (String) paras[2];

            if (StringUtils.isEmpty(value)) {
                throw new RuntimeException("dx_filter para 2 can't be null");
            }
        } catch (Exception e) {
            throw DataXException.asDataXException(TransformerErrorCode.TRANSFORMER_ILLEGAL_PARAMETER, "paras:" + Arrays.asList(paras).toString() + " => " + e.getMessage());
        }


        Column column = record.getColumn(columnIndex);

        try {

View on GitHub (pinned to 80ec23d5c5)

Solutions

1. Provide exactly 3 entries: column index, operator string, comparison value (as string).
2. Cross-check against DataX transformer documentation examples before running.

Example fix

// before
"transformer": [{"name": "dx_filter", "parameter": [2]}]

// after
"transformer": [{"name": "dx_filter", "parameter": [2, ">", "100"]}]

if (!(paras.length == 3)) throw new IllegalArgumentException("dx_filter needs exactly [index, code, value]");

catch (DataXException e) when TRANSFORMER_ILLEGAL_PARAMETER: log paras and fail fast; config error, do not retry.

When it happens

Trigger: Declaring {"name":"dx_filter","parameter":[2]} or [2,">",100,extra] in the job transformer block — anything with parameter-array length != 3.

Common situations: Omitting the value to 'just filter on the operator'; adding a fourth param by copy-paste from dx_digest examples.

Related errors

• dx_filter para 2 can't be null
• dx_digest paras length must be 3
• dx_digest paras index 1 must be md5 or sha1
• dx_digest paras index 2 must be toUpperCase or toLowerCase
• dx_filter can't support code:%s

AI-assisted analysis of alibaba/DataX@80ec23d5c5 (2026-08-14). Data as JSON: /api/errors/17e2b7ebdf132492. Report an issue: GitHub.