On 3 November 2017 at 12:41, David Rowley <david.row...@2ndquadrant.com> wrote: > On 3 November 2017 at 03:26, Craig Ringer <cr...@2ndquadrant.com> wrote: >> On 2 November 2017 at 22:22, David Rowley <david.row...@2ndquadrant.com> >> wrote: >>> Maybe, but the new implementation is not going to do well with places >>> where we perform lcons(). Probably many of those places could be >>> changed to lappend(), but I bet there's plenty that need prepend. >> >> Yeah, and it's IMO significant that pretty much every nontrivial >> system with ADTs offers multiple implementations of list data >> structures, often wrapped with a common API. >> >> Java's Collections, the STL, you name it. > > I've never really looked at much Java, but I've done quite a bit of > dotnet stuff in my time and they have a common interface ICollection > and various data structures that implement that interface. Which is > implemented by a bunch of classes, something like > > ConcurrentDictionary (hash table) > Dictionary (hash table) > HashSet (hash table) > LinkedList (some kinda linked list) > List (Arrays, probably) > SortedDictionary (bst, I think) > SortedList (no idea, perhaps a btree) > SortedSet > Bag (no idea, but does not care about any order) > > Probably there are more, but the point is that they obviously don't > believe there's a one-size-fits-all type. I don't think we should do > that either. However, I've proved nothing on the performance front > yet, so that should probably be my next step.
Right. If you've done C# you've done cleaned-up, modernized Java. C# and Java both have an advantage we don't, namely JIT compilation, so they can afford to do more with common interfaces then do runtime specialization. As a pure C project we don't really have that option, so it's unlikely to be efficient for us to have a fully common interface and dynamic dispatch. Even C++ only gets away with its common interfaces in the STL because it does compile-time specialization via templates, non-virtual methods, etc. There's only so much you can perpetrate with macros and rely on the compiler to clean up before it just gets awful. So I imagine if we do land up with a couple of collections we'd probably have an AList, alcons, alappend, etc. Bit of a pain, but hardly the end of the world. -- Craig Ringer http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
