On Tue, Mar 28, 2023 at 3:25 PM Isaac Morland <isaac.morl...@gmail.com> wrote:
> On Mon, 19 Dec 2022 at 17:57, Corey Huinker <corey.huin...@gmail.com> > wrote: > >> >> Attached is my work in progress to implement the changes to the CAST() >> function as proposed by Vik Fearing. >> >> CAST(expr AS typename NULL ON ERROR) >> will use error-safe functions to do the cast of expr, and will return >> NULL if the cast fails. >> >> CAST(expr AS typename DEFAULT expr2 ON ERROR) >> will use error-safe functions to do the cast of expr, and will return >> expr2 if the cast fails. >> > > Is there any difference between NULL and DEFAULT NULL? > What I think you're asking is: is there a difference between these two statements: SELECT CAST(my_string AS integer NULL ON ERROR) FROM my_table; SELECT CAST(my_string AS integer DEFAULT NULL ON ERROR) FROM my_table; And as I understand it, the answer would be no, there is no practical difference. The first case is just a convenient shorthand, whereas the second case tees you up for a potentially complex expression. Before you ask, I believe the ON ERROR syntax could be made optional. As I implemented it, both cases create a default expression which then typecast to integer, and in both cases that expression would be a const-null, so the optimizer steps would very quickly collapse those steps into a plain old constant.
