apache/druid · error · ParseException

Could not convert value [%s] to float.

Error message

Could not convert value [%s] to float.

What it means

DimensionHandlerUtils.convertObjectToFloat converts values to float; when a String value cannot be parsed as a float (Float.parseFloat fails), this ParseException is thrown. It means text data doesn't match the declared float column type.

Source

Thrown at processing/src/main/java/org/apache/druid/segment/DimensionHandlerUtils.java:514

      } else if (valObj instanceof Number) {
        return ((Number) valObj).floatValue();
      } else if (valObj instanceof String) {
        Float ret = Floats.tryParse((String) valObj);
        if (reportParseExceptions && ret == null) {
          final String message;
          if (fieldName != null) {
            message = StringUtils.nonStrictFormat(
                "Could not convert value [%s] to float for dimension [%s].",
                valObj,
                fieldName
            );
          } else {
            message = StringUtils.nonStrictFormat(
                "Could not convert value [%s] to float.",
                valObj
            );
          }
          throw new ParseException((String) valObj, message);
        }
        return ret;
      } else if (valObj instanceof List) {
        final String message;
        if (fieldName != null) {
          message = StringUtils.nonStrictFormat(
              "Could not ingest value [%s] as float for dimension [%s]. A float column cannot have multiple values in the same row.",
              valObj,
              fieldName
          );
        } else {
          message = StringUtils.nonStrictFormat(
              "Could not ingest value [%s] as float. A float column cannot have multiple values in the same row.",
              valObj
          );
        }
        throw new ParseException(
            valObj.getClass().toString(),

View on GitHub (pinned to 9b90983fd2)

Solutions

  1. Normalize the string in a transform (replace comma decimal separator, trim) before float conversion.
  2. Fix upstream producers to emit parseable floats (e.g. "3.14").
  3. Change column type to string if values are not reliably numeric.
  4. Configure ingestion error tolerance (maxParseExceptions / use of error handlers) so bad rows are logged instead of failing the job.

Example fix

// before: value "1,234.5" fails Float.parseFloat
// after: transform strips commas
"transforms": [{"type": "expression", "name": "price", "expression": "CAST(replace(price, ',', '') AS DOUBLE)"}]
Defensive patterns

Strategy: try-catch

Validate before calling

boolean isParsableFloat(Object v) {
  if (v == null) return true;
  if (v instanceof Number) return true;
  if (v instanceof String) {
    try { Float.parseFloat(((String) v).trim()); return true; } catch (NumberFormatException e) { return false; }
  }
  return false;
}

Type guard

Float asFloat(Object v) {
  if (v instanceof Number) return ((Number) v).floatValue();
  if (v instanceof String) { try { return Float.parseFloat(((String) v).trim()); } catch (NumberFormatException e) { return null; } }
  return null;
}

Try / catch

try {
  return DimensionHandlerUtils.convertObjectToFloat(value, fieldName);
} catch (ParseException e) {
  log.warn("Non-float value [%s] for field [%s], skipping", value, fieldName);
  return null;
}

Prevention

When it happens

Trigger: Ingesting "abc", "1,5", or empty string into a column typed float; convertObjectToFloat invoked with a non-numeric string.

Common situations: Locale decimal commas ("3,14") in input; whitespace or currency symbols in numbers; malformed rows in CSV/TSV feeds mapped to float columns.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

AI-assisted analysis of apache/druid@9b90983fd2 (2026-09-07). Data as JSON: /api/errors/8dfa40db60a8330d. Report an issue: GitHub.