private void storeIndexNameVariableValue(final String value) {
        try {
            if (!value.isEmpty() && indexNameVariables.contains(currentDocFieldName)) {
                currentDocIndexNameVariables.put(currentDocFieldName, value);
            }
        } catch (IllegalArgumentException e) {
            fatalError("Index variable '" + currentDocFieldName + "' specified more than once in document", e);
        } catch (Exception e) {
            fatalError("Unexpected error parsing index name variable value", e);
        }
    }
Whether to include the field in the destination document
stroom-search/stroom-search-elastic/src/main/java/stroom/search/elastic/indexing/ElasticIndexingFilter.java