RE: sqlite3

[Drew Adams]

> > but I didn't quite see how that would work with circular and
> > self-referential lists.)
>
> They don’t really make sense when storing to
> external storage, at least for all the mechanisms
> either you or I have. Because our storage mechanism
> doesn’t preserve intensional identity (“object identity”),
> i.e. if two objects are EQ, we store them into different key,
> they might be read back not EQ. We only store extensional
> value. In such case, circular list are no different from
> an infinite non-circular list, which doesn’t make sense.
> 
> Plus it’s not very common in practice to store circular list
> in something one may want to make persistent. Mostly
> it’s some history variable or so that is push into/delete from,
> neither will make it circular.

FWIW, I do this with bookmarks, with no problem.

But option `bmkp-propertize-bookmark-names-flag'
lets you turn this off (it's non-nil by default):

 Non-nil means to propertize bookmark names to hold full bookmark data.
 This means that you can effectively have more than one bookmark with
 the same name.

In particular, the bookmark name, which is the
car of a bookmark, is a string with a property
that holds the entire bookmark.  The bookmark
is a list with shared (circular) structure.

Emacs has no trouble writing and reading such
lists.

Perhaps you mean something special by "at least
for all the mechanisms either you or I have"?