Stephen Frost <sfrost@xxxxxxxxxxx> writes: > * Guyren Howe (guyren@xxxxxxxxx) wrote: >> It seems as though a Composite Type having only fixed-length fields should be able to be regarded as a fixed-length value. > While I can understand where you're coming from with that, it's > certainly not something the system is built to handle today and, at > least from my recent review of this area, looks like there would be a > fair bit of code involved to get to that point. There are some other fundamental problems here: * To conclude that a tuple of only fixed-length column types is itself fixed-length, you need an additional assumption that all the columns are not-null. This is pretty problematic because we don't even have a way to enforce such a requirement against generic composite types; we really only promise to enforce column constraints against columns of physical tables. * Even if all the semantic enforcement of that were bulletproof, we'd still have a big problem with compatibility of the on-disk representation between current releases and a future release that thought it could elide some part of the tuple header for all-not-null stored composite values. I don't say that these problems are insoluble, but they do look pretty difficult. regards, tom lane
