apache/cassandra · error · ParseError

Empty values are not allowed

Error message

Empty values are not allowed

What it means

During COPY FROM conversion, a mandatory (non-varchar) column value equals self.nullval (the marker for null, usually an empty string). Nulls are not representable in collections and non-varchar columns cannot receive the null marker, so a ParseError is raised.

Source

Thrown at pylib/cqlshlib/copyutil.py:1923

        """
        Return a function that converts a string into a value the can be passed
        into BoundStatement.bind() for the given cql type. See cassandra.cqltypes
        for more details.
        """
        unprotect = self.unprotect

        def convert(t, v):
            v = unprotect(v)
            if v == self.nullval:
                return self.get_null_val()
            return converters.get(t.typename, convert_unknown)(v, ct=t)

        def convert_mandatory(t, v):
            v = unprotect(v)
            # we can't distinguish between empty strings and null values in csv. Null values are not supported in
            # collections, so it must be an empty string.
            if v == self.nullval and not issubclass(t, VarcharType):
                raise ParseError('Empty values are not allowed')
            return converters.get(t.typename, convert_unknown)(v, ct=t)

        def convert_blob(v, **_):
            if sys.version_info.major >= 3:
                return bytes.fromhex(v[2:])
            else:
                return BlobType(v[2:].decode("hex"))

        def convert_text(v, **_):
            return str(v)

        def convert_uuid(v, **_):
            return UUID(v)

        def convert_bool(v, **_):
            return True if v.lower() == self.boolean_styles[0].lower() else False

        def get_convert_integer_fcn(adapter=int):

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Fix the CSV to supply valid values for non-varchar columns, or a proper null marker if the column type allows
2. Use the NULLS='<marker>' COPY option to distinguish empty string from null and make sure the marker does not collide with real data
3. Change the column type to text/varchar if empty strings are legitimately expected

Example fix

// before (CSV)
1,,2026-01-01
// after
1,0,2026-01-01
// or: COPY t FROM 'f.csv' WITH NULLS='__NULL__'

nullval = '__NULL__'  # choose marker via NULLS option
for row in csv_rows:
    for i, v in enumerate(row):
        if v == '' and col_types[i] not in ('text','varchar'):
            raise ValueError(f"row {row}: empty mandatory field {i}")

try:
    session.execute(copy_from_import)
except ParseError as e:
    log.error(f"Bad CSV value: {e}")  # locate row and fix

When it happens

Trigger: COPY FROM a CSV row where a column of a non-text type (int, timestamp, collection element, etc.) contains the nullval string (default '') — i.e. an empty CSV cell for a mandatory non-varchar column.

Common situations: Exported CSV with empty cells for numeric/date columns; NULLS= option set to a string that appears in the data; a collection element left empty in the CSV.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• Invalid row length %d should be %d
• Invalid composite string, it should start and end with match
• can't interpret %r as a date with format %s or as int
• Failed to parse %s : %s
• Invalid boolean styles %s

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/1ea9af03c4948b92. Report an issue: GitHub.