A system, method, and apparatus are provided for organizing and joining massive sets of data (e.g., tens or hundreds of millions of event records). A dataset is Blocked by first identifying a partition key, which comprises one or more columns of the data. Each Block will contain all dataset records that have partition key values assigned to that Block. A cost constraint (e.g., a maximum size, a maximum number of records) may also be applied to the Blocks. A Block index is generated to identify all Blocks, their corresponding (sequential) partition key values, and their locations. A second dataset that includes the partition key column(s) and that must be correlated with the first dataset may then be Blocked according to the same ranges of partition key values (but without the cost constraint). Corresponding Blocks of the datasets may then be Joined/Aggregated, and analyzed as necessary.