code: func (s *store) GetMinTransientBlkHt() (uint64, error) {
  	// Current approach performs a range query on purgeIndex with startKey
  	// as 0 (i.e., blockHeight) and returns the first key which denotes
  	// the lowest block height remaining in transient store. An alternative approach
  	// is to explicitly store the minBlockHeight in the transientStore.
  	startKey := createPurgeIndexByHeightRangeStartKey(0)
  	iter := s.db.GetIterator(startKey, nil)
  	defer iter.Release()
  	// Fetch the minimum transient block height
  	if iter.Next() {
  		dbKey := iter.Key()
  		_, _, blockHeight := splitCompositeKeyOfPurgeIndexByHeight(dbKey)
  		return blockHeight, nil
  	}
  	// Returning an error may not be the right thing to do here. May be
  	// return a bool. -1 is not possible due to unsigned int as first
  	// return value
  	return 0, ErrStoreEmpty
  }
docs: // GetMinTransientBlkHt returns the lowest block height remaining in transient store