1. A computer system for minimizing join operation processing time within a database system based on estimated joined table spread of the database system, the computer system comprising: one or more processors, one or more computer-readable memories, one or more computer-readable tangible storage devices and program instructions which are stored on at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories, the program instructions comprising: program instructions to estimate value distribution of data in a joined table, wherein the joined table is a result of join operation between two instances of tables of a database system; program instructions to determine boundaries for partitioning at least one range of attributes of the estimated value distribution, wherein the boundaries for partitioning at least one range of attributes of the estimated value distribution corresponds to a same number of rows of the joined table; and program instructions to determine at least one assignment of the determined partition of the at least one range of attributes to processing units of the database system.