public int getEventIdFieldIndex() {
        if (eventIdFieldIndex == null) {
            eventIdFieldIndex =
                    Optional.ofNullable(getPos(DEFAULT_EVENT_ID_FIELD_NAME))
                            .or(() -> Optional.ofNullable(
                                    getPos(FALLBACK_EVENT_ID_FIELD_NAME)))
                            .or(() -> {
                                create(FALLBACK_EVENT_ID_FIELD_NAME);
                                return Optional.ofNullable(
                                        getPos(FALLBACK_EVENT_ID_FIELD_NAME));
                            }).orElse(-1);
        }
        return eventIdFieldIndex;
    }
@return True if fieldName matches the special Event ID field.
stroom-query/stroom-query-language/src/main/java/stroom/query/language/functions/FieldIndex.java