1. A method performed by a custom index recommender system, the method comprising: capturing a query that is directed to a multi-tenant database; determining whether the captured query is a candidate for a custom index by a query identification tool of the system; determining operators used by the captured query if the query is a candidate; determining data types of the database used by the captured query if the query is a candidate; determining whether there is a current custom index for the operator and data types used by the captured query if the query is a candidate; writing the captured query to a query table of custom index candidates of the system, the query table containing a plurality of queries that have been selected for a custom index, an identifier for each query, and filters used by each query; selecting the captured query from the query table based on the determined operators, data types, and the determined current custom indexes; and generating a new custom index for the selected query based on the determined operators, data types, and the determined custom indexes.