@PipelineProperty(
            description = "The depth of XML elements to split at.",
            defaultValue = "1",
            displayPriority = 1)
    public void setSplitDepth(final int splitDepth) {
        // Add a fudge in here to cope with legacy depth being 0 based.
        this.splitDepth = splitDepth + 1;
    }
Make sure the event array is going to be big enough to hold the item that
is just about to be added.
stroom-pipeline/src/main/java/stroom/pipeline/filter/SplitFilter.java