On the the "Supported Data Types" page at http://drill.apache.org/docs/supported-data-types/, the first subsection (before the "Casting and Converting Data Types" subsection) doesn't include composite types (arrays and maps). Since that subsection seems to be intended to be the orientation to the set of data types that are available in Drill, it should include composite types as well as the atomic types it already includes.
For those composite types, it should mention the key type-specific operations on those types (i.e., for arrays: array element references (SQL's <array element reference> construct, e.g., a); for maps: the construct(s) that Drill provides for referring to the value for a given key, e.g., m['k']). (It should probably also have links to the sections, pages, or subsections for the special functions for those types (e.g., KVGEN, FLATTEN).)
(Note that although the text "SQL data types for query input" seems (depending the interpretation of "query input") to indicate that the section was conceived of to document the set of data types for which users can give literal values in SQL queries, that apparent intent should be widened to the set of data types that users deal with in queries.
For example, even though users can't (yet) give a value of an array type in a query, they can deal with array values coming from data sources, e.g., by indexing the array value to get a specific element of each array value.)