code: protected void doDelete(String spaceId, String key) throws IOException {
          Term termDelete = buildIdTerm(spaceId, key);
          IndexWriter indexWriter = getIndexWriter();
          indexWriter.deleteDocuments(termDelete);
          if (!isAsyncWrite()) {
              indexWriter.commit();
          } else if (getIndexManager().getBackgroundCommitIndexPeriodMs() <= 0) {
              LOGGER.warn("Async-write is enable, autoCommitPeriodMs must be larger than 0!");
          }
      }
docs: Delete a document, identified by {@code spaceId:key}, from index.
  
  @param spaceId
  @param key
  @throws IOException