Re: WIP Incremental JSON Parser

On Wed, Jan 3, 2024 at 6:36 PM Nico Williams <nico@cryptonector.com> wrote:
> On Tue, Jan 02, 2024 at 10:14:16AM -0500, Robert Haas wrote:
> > It seems like a pretty significant savings no matter what. Suppose the
> > backup_manifest file is 2GB, and instead of creating a 2GB buffer, you
> > create an 1MB buffer and feed the data to the parser in 1MB chunks.
> > Well, that saves 2GB less 1MB, full stop. Now if we address the issue
> > you raise here in some way, we can potentially save even more memory,
> > which is great, but even if we don't, we still saved a bunch of memory
> > that could not have been saved in any other way.
>
> You could also build a streaming incremental parser.  That is, one that
> outputs a path and a leaf value (where leaf values are scalar values,
> `null`, `true`, `false`, numbers, and strings).  Then if the caller is
> doing something JSONPath-like then the caller can probably immediately
> free almost all allocations and even terminate the parse early.

I think our current parser is event-based rather than this ... but it
seems like this could easily be built on top of it, if someone wanted
to.

--
Robert Haas
EDB: http://www.enterprisedb.com