1. A method for applying database partitioning in a multi-tenancy scenario, comprising: providing, in each database table of a partitioned database system storing tenant data for a plurality of tenants, a partition key field for storing a respective partition key for each tenant within the plurality of tenants, wherein the partitioned database system stores data across a plurality of partitions, wherein each tenant is assigned to at least one respective partition, and wherein a subset plurality of tenants is assigned to one partition within the plurality of partitions, wherein the subset plurality of tenants is a subset of the plurality of tenants; maintaining a mapping between partition keys and partitions within the plurality of partitions, the mapping between partition keys and partitions indicating, for each tenant, the respective partition key and a respective partition designated to the each tenant according to corresponding relationships between partitions and partition keys in the database partitioning mechanism of the partitioned database system, wherein partition keys are different from identifiers of the respective partitions; in response to a new tenant on-boarding, designating a designated partition within the plurality of partitions, the designated partition being used to store data for the tenant; determining, in response to the designating, a new partition key associated with the designated partition according to the corresponding relationships between partitions and partition keys in the database partitioning mechanism; storing a corresponding relationship between the new tenant and the new partition key into the mapping; and performing database partitioning operations on the data of each respective tenant based upon the respective partition key and the mapping between partition keys and partitions.