prestodb/presto · error · IndexOutOfBoundsException

Invalid position %s and length %s in block with %s positions

Error message

Invalid position %s and length %s in block with %s positions

What it means

BlockUtil.checkValidRegion validates a region view (positionOffset, length) against a block's positionCount, throwing IndexOutOfBoundsException when positionOffset is negative, length is negative, or positionOffset+length exceeds positionCount. It guards Block.getRegion-style slicing so no region references positions outside the block.

Source

Thrown at presto-common/src/main/java/com/facebook/presto/common/block/BlockUtil.java:61

    {
        requireNonNull(array, "array is null");
        if (offset < 0 || length < 0 || offset + length > array.length) {
            throw new IndexOutOfBoundsException(format("Invalid offset %s and length %s in array with %s elements", offset, length, array.length));
        }
    }

    static void checkArrayRange(boolean[] array, int offset, int length)
    {
        requireNonNull(array, "array is null");
        if (offset < 0 || length < 0 || offset + length > array.length) {
            throw new IndexOutOfBoundsException(format("Invalid offset %s and length %s in array with %s elements", offset, length, array.length));
        }
    }

    static void checkValidRegion(int positionCount, int positionOffset, int length)
    {
        if (positionOffset < 0 || length < 0 || positionOffset + length > positionCount) {
            throw new IndexOutOfBoundsException(format("Invalid position %s and length %s in block with %s positions", positionOffset, length, positionCount));
        }
    }

    static void checkValidPositions(boolean[] positions, int positionCount)
    {
        if (positions.length != positionCount) {
            throw new IllegalArgumentException(format("Invalid positions array size %d, actual position count is %d", positions.length, positionCount));
        }
    }

    static void checkValidPosition(int position, int positionCount)
    {
        if (position < 0 || position >= positionCount) {
            throw new IllegalArgumentException(format("Invalid position %s in block with %s positions", position, positionCount));
        }
    }

    static void checkValidSliceRange(int sourceIndex, int length)

View on GitHub (pinned to 55bb57d202)

Solutions

Clamp positionOffset/length to the block's getPositionCount() before slicing
Use getRegionLength()/getSliceLength to derive length instead of hardcoding
Catch IndexOutOfBoundsException and surface which block and offsets were invalid

Example fix

// before
Block region = block.getRegion(offset, remaining);
// after
int len = Math.min(remaining, block.getPositionCount() - offset);
Block region = block.getRegion(offset, len);

Defensive patterns

Strategy: validation

Validate before calling

if (positionOffset < 0 || length < 0 || positionOffset > positionCount - length) {
    throw new IllegalArgumentException("bad region: offset=" + positionOffset + " length=" + length + " positions=" + positionCount);
}

Type guard

boolean isValidRegion(int positionCount, int positionOffset, int length) {
    return positionOffset >= 0 && length >= 0 && positionOffset <= positionCount - length;
}

Try / catch

try {
    region = block.getRegion(positionOffset, length);
} catch (IndexOutOfBoundsException e) {
    throw new PrestoException(GENERIC_INTERNAL_ERROR, "invalid region " + positionOffset + "+" + length + " of " + block.getPositionCount(), e);
}

Prevention

Clamp requested length against block.getPositionCount() before slicing
Derive region bounds from the block API (getRegionLength) rather than cached sizes
Add assertions on offset math in custom Block implementations

When it happens

Trigger: Calling Block.getRegion (or a custom block that calls checkValidRegion) with a positionOffset or length computed from bad row math — e.g. requesting more positions than the block holds, or offset+length overflowing int.

Common situations: Paging/streaming code that assumes blocks always carry a fixed position count; cursor arithmetic bugs after partial reads; custom Block subclasses passing regionLength defaults larger than the block.

Related errors

AI-assisted analysis of prestodb/presto@55bb57d202 (2026-09-04). Data as JSON: /api/errors/6655b242512573a4. Report an issue: GitHub.