code: func (e *executor) executeXorShard(ctx context.Context, index string, c *pql.Call, shard uint64) (*Row, error) {
  	span, ctx := tracing.StartSpanFromContext(ctx, "Executor.executeXorShard")
  	defer span.Finish()
  
  	other := NewRow()
  	for i, input := range c.Children {
  		row, err := e.executeBitmapCallShard(ctx, index, input, shard)
  		if err != nil {
  			return nil, err
  		}
  
  		if i == 0 {
  			other = row
  		} else {
  			other = other.Xor(row)
  		}
  	}
  	other.invalidateCount()
  	return other, nil
  }
docs: // executeXorShard executes a xor() call for a local shard.