David Johnston <polobo@xxxxxxxxx> writes: > Tom Lane-2 wrote >> you do have one conceptual error: anyarray to anyelement is supposed >> to return the element type of the input array type. So when you pass >> TEXT[] to this function, the SQL parser decides that the expected >> result type is TEXT. > While this is how it behaves in practice I did not find this described in > the documentation. No? What I read in http://www.postgresql.org/docs/9.3/static/extend-type-system.html#EXTEND-TYPES-POLYMORPHIC is: Polymorphic arguments and results are tied to each other and are resolved to a specific data type when a query calling a polymorphic function is parsed. Each position (either argument or return value) declared as anyelement is allowed to have any specific actual data type, but in any given call they must all be the same actual type. Each position declared as anyarray can have any array data type, but similarly they must all be the same type. And similarly, positions declared as anyrange must all be the same range type. Furthermore, if there are positions declared anyarray and others declared anyelement, the actual array type in the anyarray positions must be an array whose elements are the same type appearing in the anyelement positions. The last sentence is what I was saying, no? You can if you like replace "anyelement" by "anynonarray", but that won't change the semantics if there's also an occurrence of "anyarray", because that's going to constrain the anyelement type to be something that has an associated array type. (If we had arrays of arrays, then these two cases might differ ... but we don't.) FWIW, the original design for polymorphic functions didn't have anynonarray, and we didn't particularly need it. My recollection is that it's basically a kludge that we invented later to allow the text concatenation and array concatenation versions of "||" to coexist. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
