presto-spi/src/main/java/io/prestosql/spi/block/RowBlock.java/RowBlock/getLoadedBlock
class RowBlock:    @Override
    public Block getLoadedBlock()
    {
        boolean allLoaded = true;
        Block[] loadedFieldBlocks = new Block[fieldBlocks.length];

        for (int i = 0; i < fieldBlocks.length; i++) {
            loadedFieldBlocks[i] = fieldBlocks[i].getLoadedBlock();
            if (loadedFieldBlocks[i] != fieldBlocks[i]) {
                allLoaded = false;
            }
        }

        if (allLoaded) {
            return this;
        }
        return createRowBlockInternal(
                startOffset,
                positionCount,
                rowIsNull,
                fieldBlockOffsets,
                loadedFieldBlocks);
    }