1. A computer-implemented method of improving a query, the method comprising: receiving at a network interface of a server in a multi-tenant database system an original query transmitted to the multi-tenant database system by a user associated with a tenant, wherein the original query is associated with data accessible by the tenant, and wherein the multi-tenant database system includes at least a first index and a second index; retrieving, using a processor of the server, metadata associated with the data accessible by the tenant in the multi-tenant database system, wherein at least a portion of the data accessible by the tenant is stored in a common table within the multi-tenant database system; determining, using the processor, a tenant-selective query syntax, wherein determining comprises analyzing at least one of metadata generated from information about the tenant or metadata generated from the data accessible by the tenant; and generating, using the processor, an improved query using the query syntax, wherein the improved query is based at least in part upon the original query and a result of a join between a first number of rows associated with the first index and a second number of rows associated with the second index.