1. A system comprising: one or more processors; and program code including a query optimizer, the program code configured to be executed by the one or more processors to process a database query, the program code configured to: create an access control bit mapping (ACBM) structure for a database table in a memory, the database table having a number of database rows, each database row including an access control field value selected from a plurality of candidate access control field values, the access control field value designating access rights to the database row, the ACBM structure having a number of entries, each entry including a parameter field value designating the access rights associated with at least one of the plurality of candidate access control field values, each entry further including a relative record number (RRN) bit map, the RRN bit map having a number of bits corresponding to the number of database rows in the database table, each bit indicating whether the parameter field value designates the access rights determined by the access control field value of the corresponding database row, wherein the parameter field value of a first entry in the ACBM structure designates first access rights, wherein a target number of database rows are accessible under the first access rights, and wherein the target number of bits in the RRN bit map of the first entry identifies the corresponding accessible database rows; determine one or more statistics from the RRN bit map, wherein the one or more statistics correspond to accessible rows of the database table associated with the parameter field value; and update the ACBM structure in response to determining that the database table has been modified, the update including modifying the RRN bit map of at least one entry.