Exemplary method, system, and computer program product embodiments for real-time column compression of data are provided. In one embodiment, by way of example only, a data structure is estimated for an initially unknown structured data. The estimated data structure is placed in a stream. A columnar compression operation is applied to the stream to generate an achieved compression ratio. The stream is compressed. Feedback of the achieved compression ratio is analyzed from the stream to determine if an optimal one of the columnar compression operations has been applied. If the optimal one of the columnar compression operations has been applied, the actual data structure of the initially unknown structured data is determined.