prestodb/presto · error · IllegalArgumentException

positionCount is negative

Error message

positionCount is negative

What it means

IntArrayBlock requires a non-negative positionCount. Negative counts are impossible block sizes and indicate a caller bug (e.g. subtracting lengths or passing a sentinel), so the constructor throws IllegalArgumentException before any data is stored.

Source

Thrown at presto-common/src/main/java/com/facebook/presto/common/block/IntArrayBlock.java:63

    @Nullable
    private final boolean[] valueIsNull;
    private final int[] values;

    private final long retainedSizeInBytes;

    public IntArrayBlock(int positionCount, Optional<boolean[]> valueIsNull, int[] values)
    {
        this(0, positionCount, valueIsNull.orElse(null), values);
    }

    IntArrayBlock(int arrayOffset, int positionCount, boolean[] valueIsNull, int[] values)
    {
        if (arrayOffset < 0) {
            throw new IllegalArgumentException("arrayOffset is negative");
        }
        this.arrayOffset = arrayOffset;
        if (positionCount < 0) {
            throw new IllegalArgumentException("positionCount is negative");
        }
        this.positionCount = positionCount;

        if (values.length - arrayOffset < positionCount) {
            throw new IllegalArgumentException("values length is less than positionCount");
        }
        this.values = values;

        if (valueIsNull != null && valueIsNull.length - arrayOffset < positionCount) {
            throw new IllegalArgumentException("isNull length is less than positionCount");
        }
        this.valueIsNull = valueIsNull;

        retainedSizeInBytes = INSTANCE_SIZE + sizeOf(valueIsNull) + sizeOf(values);
    }

    @Override
    public long getSizeInBytes()

View on GitHub (pinned to 55bb57d202)

Solutions

1. Validate end >= start (or count >= 0) before constructing the block.
2. Fix the arithmetic that derives positionCount (e.g. Math.abs is wrong — correct the subtraction order).
3. Sanitize counts read from external/serialized sources before constructing blocks.

Example fix

// before
int count = endIdx - startIdx; // endIdx < startIdx -> negative
// after
int count = Math.max(0, endIdx - startIdx);

if (positionCount < 0) {
    throw new IllegalArgumentException("positionCount must be non-negative");
}
IntArrayBlock block = new IntArrayBlock(arrayOffset, positionCount, valueIsNull, values);

boolean nonNegativeCount(int positionCount) { return positionCount >= 0; }

try {
    block = new IntArrayBlock(offset, count, nulls, values);
} catch (IllegalArgumentException e) {
    block = IntArrayBlock.EMPTY_BLOCK; // or recompute count
}

When it happens

Trigger: Calling new IntArrayBlock(arrayOffset, positionCount, ...) with positionCount < 0, usually from length arithmetic like end - start where end < start.

Common situations: Slicing pages where start/end indexes got swapped; aggregate code subtracting consumed positions from a smaller total; deserializers reading a corrupted negative count field.

Related errors

• arrayOffset is negative
• Offset is not monotonically ascending. offsets[%s]=%s, offse
• A null map must have zero entries
• Number of fields in RowBlock must be positive
• position is not valid

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/73b904818262b01f. Report an issue: GitHub.