OpenRefine/OpenRefine · error · IllegalArgumentException

Inconsistent number of properties fetched and of result…

Error message

Inconsistent number of properties fetched and of result column names

What it means

The ExtendDataOperation constructor validates that the number of properties in the column extension matches the number of supplied result column names, since each fetched property maps to exactly one new column. A mismatch throws an IllegalArgumentException in the constructor.

Solutions

1. Make resultColumnNames contain exactly one name per property in the extension, in the same order
2. Regenerate the operation via the 'Add columns from reconciled values' dialog instead of editing JSON
3. If using the deprecated legacy constructor, migrate to the constructor/API that takes explicit column names
4. Count extension.properties and adjust resultColumnNames to the same length

Example fix

// before: 2 properties, 1 name
new ExtendDataOperation(base, "wd:Q1", ids, schema, ext(2 props), 1, List.of("name"))
// after
new ExtendDataOperation(base, "wd:Q1", ids, schema, ext(2 props), 1, List.of("name","birthdate"))

if (extension.properties.length !== resultColumnNames.length) {
  throw new Error('resultColumnNames must have one entry per extension property');
}

try {
  ExtendDataOperation op = new ExtendDataOperation(...);
} catch (IllegalArgumentException e) {
  if (e.getMessage().contains("Inconsistent number of properties")) {
    // fix the column name list
  }
}

When it happens

Trigger: Constructing ExtendDataOperation (or deserializing it from operation JSON) where extension.properties.length != resultColumnNames.length, e.g. hand-editing the JSON to add properties without updating column names.

Common situations: Writing 'Add columns from reconciled values' operations programmatically; editing exported operation JSON to add a property to fetch; upgrading legacy operations that used the deprecated no-names constructor.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Cannot manually set judgment to 'error'
• Cannot manually set judgment to 'error'
• Creation of column ' ' conflicts with an existing column…
• Input strings cannot be empty
• Invalid expression

AI-assisted analysis of OpenRefine/OpenRefine@a946177e04 (2026-09-08). Data as JSON: /api/errors/9dd8ccd3b980c6a1. Report an issue: GitHub.

Appendix: source

Thrown at main/src/com/google/refine/operations/recon/ExtendDataOperation.java:112

            @JsonProperty("engineConfig") EngineConfig engineConfig,
            @JsonProperty("baseColumnName") String baseColumnName,
            @JsonProperty("endpoint") String endpoint,
            @JsonProperty("identifierSpace") String identifierSpace,
            @JsonProperty("schemaSpace") String schemaSpace,
            @JsonProperty("extension") DataExtensionConfig extension,
            @JsonProperty("columnInsertIndex") int columnInsertIndex,
            @JsonProperty("resultColumnNames") List<String> resultColumnNames) {
        super(engineConfig);

        _baseColumnName = baseColumnName;
        _endpoint = endpoint;
        _identifierSpace = identifierSpace;
        _schemaSpace = schemaSpace;
        _extension = extension;
        _columnInsertIndex = columnInsertIndex;
        _resultColumnNames = resultColumnNames;
        if (_resultColumnNames != null && _extension.properties.size() != _resultColumnNames.size()) {
            throw new IllegalArgumentException("Inconsistent number of properties fetched and of result column names");
        }
    }

    /**
     * @deprecated legacy constructor: supply column names instead
     */
    @Deprecated(since = "3.9")
    public ExtendDataOperation(
            EngineConfig engineConfig,
            String baseColumnName,
            String endpoint,
            String identifierSpace,
            String schemaSpace,
            DataExtensionConfig extension,
            int columnInsertIndex) {
        this(engineConfig, baseColumnName, endpoint, identifierSpace, schemaSpace, extension, columnInsertIndex, null);
    }

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