private void deleteMetaRecords(final Progress progress,
                                   final Set<Long> successfulMetaIdSet,
                                   final int successCount) {
        // Physically delete meta data.
        info(() -> LogUtil.message("Deleting meta data for {} meta IDs", successCount));
        final DurationTimer metaDeleteTimer = DurationTimer.start();
        physicalDelete.cleanup(successfulMetaIdSet);
        progress.addMetaDeletionDuration(metaDeleteTimer);
        LOGGER.debug(() -> LogUtil.message("{} - Deleted {} meta records (and associated values) for in {}",
                TASK_NAME, successCount, metaDeleteTimer.get()));
    }
Deletes a batch of simpleMetas from the file system and the database.

@param deleteThresholdEpoch The threshold for statusTime, i.e. records <= deleteThresholdEpoch
@param progress             Count of failures that spans multiple batches
@return Those simpleMeta items that could not be deleted for some reason.
stroom-data/stroom-data-store-impl-fs/src/main/java/stroom/data/store/impl/fs/PhysicalDeleteExecutor.java