Re: Varlena with recursive data structures?

Hi Karl,

I'm going down this road myself. In addition to the files Tom Lane pointed
out there is also some helpful documentation here:

https://www.postgresql.org/docs/current/storage-toast.html#STORAGE-TOAST-INMEMORY

On Wed, Jan 16, 2019 at 2:09 PM Sam Patterson <katoriasdev(at)gmail(dot)com> wrote:

> Hi all,
>
> I've recently started developing an extension for Postgres for which I'll
> need to create a new variable-length base type. The type will require a
> tree-like structure in order to parse sufficiently, which of course
> probably means having some sort of recursive data structure, like a struct
> that has members which are pointers to itself for child nodes. After doing
> some research, specifically looking at how other variable-length data types
> store their data, it seems almost all of them store the data in a binary
> representation, using bit masks and offsets etc in order to store/access
> the data whilst having an in-memory representation that's used to
> manipulate the data.
>
> I presume the purpose for using this approach is because all the data in a
> varlena type has to be contiguous, and the moment you start using pointers
> this is no longer possible. So my question is, given a structure that looks
> something like this,
>
> typedef struct Node
> {
> char *data;
> Node *left;
> Node *right;
> } Node;
>
> am I right in saying that I wouldn't be able to store that representation
> on-disk, but instead I'd have to transform it into some binary
> representation and back again when writing/reading respectively, are there
> any alternatives?
>
> Regards,
>
> Karl
>