docs: private void initFromDatabase() throws SQLException, BlockStoreException {
          PreparedStatement ps = conn.get().prepareStatement(getSelectSettingsSQL());
          ResultSet rs;
          ps.setString(1, CHAIN_HEAD_SETTING);
          rs = ps.executeQuery();
          if (!rs.next()) {
              throw new BlockStoreException("corrupt database block store - no chain head pointer");
          }
          Sha256Hash hash = Sha256Hash.wrap(rs.getBytes(1));
          rs.close();
          this.chainHeadBlock = get(hash);
          this.chainHeadHash = hash;
          if (this.chainHeadBlock == null) {
              throw new BlockStoreException("corrupt database block store - head block not found");
          }
          ps.setString(1, VERIFIED_CHAIN_HEAD_SETTING);
          rs = ps.executeQuery();
          if (!rs.next()) {
              throw new BlockStoreException("corrupt database block store - no verified chain head pointer");
          }
          hash = Sha256Hash.wrap(rs.getBytes(1));
          rs.close();
          ps.close();
          this.verifiedChainHeadBlock = get(hash);
          this.verifiedChainHeadHash = hash;
          if (this.verifiedChainHeadBlock == null) {
              throw new BlockStoreException("corrupt database block store - verified head block not found");
          }
      }