apache/cassandra · error · MarshalException

Unable to make float from '%s'

Error message

Unable to make float from '%s'

What it means

FloatType.fromString() parses a CQL string into a float via Float.parseFloat(). When the string is not a valid Java float literal, NumberFormatException is caught and rethrown as a MarshalException with the original text embedded. This protects float column deserialization from malformed literal values.

Source

Thrown at src/java/org/apache/cassandra/db/marshal/FloatType.java:93

    @Override
    public <V> V fromComparableBytes(ValueAccessor<V> accessor, ByteSource.Peekable comparableBytes, ByteComparable.Version version)
    {
        return ByteSourceInverse.getOptionalSignedFixedLengthFloat(accessor, comparableBytes, 4);
    }

    public ByteBuffer fromString(String source) throws MarshalException
    {
      // Return an empty ByteBuffer for an empty string.
      if (source.isEmpty())
          return ByteBufferUtil.EMPTY_BYTE_BUFFER;

      try
      {
          return decompose(Float.parseFloat(source));
      }
      catch (NumberFormatException e1)
      {
          throw new MarshalException(String.format("Unable to make float from '%s'", source), e1);
      }
    }

    @Override
    public Term fromJSONObject(Object parsed) throws MarshalException
    {
        try
        {
            if (parsed instanceof String)
                return new Constants.Value(fromString((String) parsed));
            else
                return new Constants.Value(getSerializer().serialize(((Number) parsed).floatValue()));
        }
        catch (ClassCastException exc)
        {
            throw new MarshalException(String.format(
                    "Expected a float value, but got a %s: %s", parsed.getClass().getSimpleName(), parsed));
        }

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Correct the input to a valid float literal (e.g. '3.14', '-1e3', 'NaN')
2. Normalize locale formatting (replace ',' decimal separator, strip grouping) before parsing
3. Send JSON numbers instead of strings so fromJSONObject uses the Number branch
4. Pre-validate with Float.parseFloat in a try/catch before submitting

Example fix

// before
FloatType.instance.fromString("3,14");
// after
FloatType.instance.fromString("3.14");

boolean isValidFloatLiteral(String s) { try { Float.parseFloat(s); return true; } catch (NumberFormatException e) { return false; } }

try { FloatType.instance.fromString(source); } catch (MarshalException e) { log.warn("Invalid float literal: {}", source); }

When it happens

Trigger: Calling FloatType.instance.fromString(...) (directly or via fromJSONObject with a string value) with non-parseable text like '3,14', '1.2.3', 'abc', or an empty string.

Common situations: Locale-formatted decimal strings with commas; truncated numerics from log parsing; free-text accidentally bound to a float column.

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

• Unable to make double from '%s'
• In call to function %s, value 0x%s is not a valid binary rep
• ' is not empty
• Expected a float value, but got a %s: %s
• Unable to make inet address from '%s'

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/9cfc3143999e6606. Report an issue: GitHub.