1. A method in a host organization, the method comprising: exposing an interface to client devices operating remotely from the host organization, wherein the interface is accessible by the client devices via a public Internet; executing a predictive database at the host organization as an on-demand cloud based service for one or more subscribers; authenticating one of the client devices by verifying the client device is associated with one of the subscribers and based further on authentication credentials for the respective subscriber; processing a dataset of columns and rows to generate indices on behalf of the authenticated subscriber, the indices representing probabilistic relationships between the rows and the columns of the dataset, wherein the processing comprises: (i) processing the dataset by iteratively learning joint probability distributions over the dataset to generate the indices, (ii) periodically determining a predictive quality measure of the indices generated by the processing of the dataset, and (iii) terminating processing of the dataset when the predictive quality measure attains a specified threshold; receiving a prediction request from the authenticated subscriber via the interface; executing a query against the indices of the predictive database generated from the dataset; returning a prediction result of the query to the authenticated subscriber responsive to the prediction request; and returning a notification with the prediction result indicating processing of the stored dataset has not yet completed or returning a notification with the prediction result indicating the predictive quality measure is below the specified threshold, or returning both with the prediction result.