Amazon patents database tool to query mixed file formats

1. A system, comprising: at least one processor; and a memory, storing program instructions that when executed by the at least one processor, cause the at least one processor to implement a database system; wherein the database system is configured to: receive a query that accesses an external table stored separately from the database system, wherein the database system supports external tables stored in different file formats, including a transactional file format and a non-transaction file format, wherein the external table is stored in one of the different file formats; generate a plan to perform the query, wherein the plan comprises: a first operation to evaluate an additional table that stores metadata that describes different files that make up the external table according to the one of the different file formats; and a second operation to access the identified one of more files using respective storage locations of the different files stored in the additional table; and perform the plan to generate a result of the query, wherein to perform the query plan, the database system is configured to: cause one or more compute nodes, different from a leader node that generated the query plan, to execute the first operation to access the metadata and identify one or more files of the different files of the external table to access according to a read view determined for the query; and cause the one or more compute nodes to execute the second operation to access the identified one of more files using respective storage locations of the different files stored in the additional table; and return the result of the query.