docs: private void loadFromFile() {
      // load from disk if the caller gave us a file
      if (file_location != null && !file_location.isEmpty()) {
        final File file = new File(file_location);
        if (!file.exists()) {
          LOG.warn("Query override file " + file_location + " does not exist");
          return;
        }
        try {
          final String raw_json = Files.toString(file, Const.UTF8_CHARSET);
          if (raw_json != null && !raw_json.isEmpty()) {
            final Set<QueryLimitOverrideItem> cached_items = 
                JSON.parseToObject(raw_json, TR_OVERRIDES);
            
            // iterate so we only change bits that are different.
            for (final QueryLimitOverrideItem override : cached_items) {
              QueryLimitOverrideItem existing = overrides.get(override.getRegex());
              if (existing == null || !existing.equals(override)) {
                overrides.put(override.getRegex(), override);
              }
            }
            
            // reverse quadratic, woot! Ugly but if the limit file is so big that
            // this takes over 60 seconds or starts blocking queries on modifications
            // to the map then something is really wrong.
            final Iterator<Entry<String, QueryLimitOverrideItem>> iterator = 
                overrides.entrySet().iterator();
            while (iterator.hasNext()) {
              final Entry<String, QueryLimitOverrideItem> entry = iterator.next();
              boolean matched = false;
              for (final QueryLimitOverrideItem override : cached_items) {
                if (override.getRegex().equals(entry.getKey())) {
                  matched = true;
                  break;
                }
              }
              if (!matched) {
                iterator.remove();
              }
            }
          }
          LOG.info("Successfully loaded query overrides: " + this);
        } catch (Exception e) {
          LOG.error("Failed to read cache file for query limit override: " + 
              this, e);
        }
      }
    }