What causes "Size has to be strictly positive number, it is ' '." in apache/cassandra?

Set dictLength to the actual number of bytes in the dictionary payload (dict.length)

apache/cassandra · error · IllegalArgumentException

Size has to be strictly positive number, it is

Error message

Size has to be strictly positive number, it is '<dictLength>'.

What it means

The declared dictionary length (dictLength) must be a strictly positive number. validate() rejects dictLength <= 0 before comparing it to the actual byte array length, ensuring the descriptor always declares a meaningful payload size.

Solutions

Set dictLength to the actual number of bytes in the dictionary payload (dict.length)
If reading from a file, use the file size after verifying it is non-empty
Initialize the length field rather than leaving it at its numeric default

Example fix

// before
int dictLength = 0; // unset
// after
int dictLength = dict.length;

Defensive patterns

Strategy: validation

Validate before calling

if (obj.dictLength <= 0) throw new IllegalArgumentException("dictLength must be positive, got: " + obj.dictLength);

Type guard

boolean hasPositiveLength(CompressionDictionaryDataObject o) { return o.dictLength > 0; }

Try / catch

try { tabularData.fromDataObject(obj); } catch (IllegalArgumentException e) { if (e.getMessage().startsWith("Size has to be strictly positive")) { /* set dictLength = dict.length and rebuild */ } else throw e; }

Prevention

Derive dictLength directly from dict.length so it can never default to 0
Avoid unset numeric defaults; compute lengths at construction time
Check the payload was actually loaded before declaring its length

When it happens

Trigger: Constructing a CompressionDictionaryDataObject with dictLength = 0 or negative — typically an unset numeric field (default 0) or a length variable computed from an empty/failed read.

Common situations: Import tooling where the length field defaulted to 0; lengths parsed from a truncated metadata source; callers passing byte count of an empty buffer.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/d269782431da1efa. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/compression/CompressionDictionaryDetailsTabularData.java:312

                throw new IllegalArgumentException("Provided dictionary id must be positive but it is '" + dictId + "'.");
            if (dict == null || dict.length == 0)
                throw new IllegalArgumentException("Provided dictionary byte array is null or empty.");
            if (kind == null)
                throw new IllegalArgumentException("Provided kind is null.");

            CompressionDictionary.Kind dictionaryKind;

            try
            {
                dictionaryKind = CompressionDictionary.Kind.valueOf(kind);
            }
            catch (IllegalArgumentException ex)
            {
                throw new IllegalArgumentException("There is no such dictionary kind like '" + kind + "'. Available kinds: " + Arrays.asList(CompressionDictionary.Kind.values()));
            }

            if (dictLength <= 0)
                throw new IllegalArgumentException("Size has to be strictly positive number, it is '" + dictLength + "'.");
            if (dict.length != dictLength)
                throw new IllegalArgumentException("The length of the provided dictionary array (" + dict.length + ") is not equal to provided length value (" + dictLength + ").");
            if (createdAt == null)
                throw new IllegalArgumentException("The creation date not specified.");

            int checksumOfDictionaryToImport = CompressionDictionary.calculateChecksum((byte) dictionaryKind.ordinal(), dictId, dict);
            if (checksumOfDictionaryToImport != dictChecksum)
            {
                throw new IllegalArgumentException(format("Computed checksum of dictionary to import (%s) is different from checksum specified on input (%s).",
                                                          checksumOfDictionaryToImport,
                                                          dictChecksum));
            }
        }
    }
}

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