dotnet/machinelearning · error · ArgumentException

Strings.MapIndicesExceedsColumnLength

Error message

Strings.MapIndicesExceedsColumnLength

What it means

CloneImplementation(PrimitiveDataFrameColumn<bool> boolColumn) uses the bool column as a filter map, so it must not be longer than the source column; when boolColumn.Length > Length it throws ArgumentException(Strings.MapIndicesExceedsColumnLength, nameof(boolColumn)). Reached via Clone when mapIndices is a bool column.

Solutions

1. Trim the bool mask to the column's Length before cloning.
2. Build the mask from the same column/DataFrame so lengths always match.
3. Assert boolColumn.Length <= column.Length before calling Clone.
4. Use a long/int index column instead of a bool mask when lengths may differ.

Example fix

// before
var clone = column.Clone(mask); // mask.Length > column.Length
// after
if (mask.Length > column.Length)
    throw new ArgumentException("Mask longer than column");
var clone = column.Clone(mask);

if (mask is PrimitiveDataFrameColumn<bool> boolMask && boolMask.Length > column.Length)
    throw new ArgumentException("Bool mask longer than column");

bool isValidMask(PrimitiveDataFrameColumn<bool> mask, DataFrameColumn col) => mask.Length <= col.Length;

try { var clone = column.Clone(mask); }
catch (ArgumentException ex) when (ex.ParamName == "boolColumn")
{ /* mask longer than column: trim mask */ }

When it happens

Trigger: Calling Clone(mapIndices) where mapIndices is a PrimitiveDataFrameColumn<bool> with more entries than the VBufferDataFrameColumn being cloned.

Common situations: Filter masks built from a longer DataFrame reused against a shorter column; mask columns that grew after earlier appends; combining columns of differing lengths.

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

• String.Format(Strings.MultipleMismatchedValueType…
• and must be different
• Column lengths are mismatched
• nameof(groupByColumnIndex)
• string.Format(Strings.DuplicateColumnName, column.Name)

AI-assisted analysis of dotnet/machinelearning@7b76e69cf9 (2026-09-11). Data as JSON: /api/errors/c4768d97c24f9193. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.Data.Analysis/DataFrameColumns/VBufferDataFrameColumn.cs:215

            if (Length > row)
            {
                this[row] = value;
            }
            else if (Length == row)
            {
                Append(value);
            }
            else
            {
                throw new IndexOutOfRangeException(nameof(row));
            }
        }

        private VBufferDataFrameColumn<T> CloneImplementation(PrimitiveDataFrameColumn<bool> boolColumn)
        {
            if (boolColumn.Length > Length)
                throw new ArgumentException(Strings.MapIndicesExceedsColumnLength, nameof(boolColumn));
            VBufferDataFrameColumn<T> ret = new VBufferDataFrameColumn<T>(Name, 0);
            for (long i = 0; i < boolColumn.Length; i++)
            {
                bool? value = boolColumn[i];
                if (value.HasValue && value.Value == true)
                    ret.Append(this[i]);
            }
            return ret;
        }

        private VBufferDataFrameColumn<T> CloneImplementation(PrimitiveDataFrameColumn<long> mapIndices, bool invertMapIndices = false)
        {
            mapIndices = mapIndices ?? throw new ArgumentNullException(nameof(mapIndices));
            var ret = new VBufferDataFrameColumn<T>(Name, mapIndices.Length);

            long rowIndex = 0;
            for (int b = 0; b < mapIndices.ColumnContainer.Buffers.Count; b++)
            {

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