The text discusses the power of advanced RDBMS features in PostgreSQL, specifically partial and expression indexes. A partial index is built over a subset of rows in a table defined by a conditional expression, reducing the size of the index and speeding up queries that use the index. In contrast, an expression index allows access to tables based on computed results from one or more columns of the underlying table, enabling fast access to tables based on the results of computations. The text highlights the differences between partial and expression indexes, providing examples of their usage in a PostgreSQL database, including a case where a partial unique index is used to ensure that no two users have the same non-null email address.