Re: About query-qmp-schema

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Apr 22, 2026 at 01:35:31PM +0200, Markus Armbruster wrote:
> Marc-André Lureau <marcandre.lureau@gmail.com> writes:
> 

snip

> >>                       and it may be a type that is not even used by
> >> qmp commands/events.
> 
> Yes, because query-qmp-schema returns the *QMP* schema.
> 
> >>                      A quick test shows the current schema is about
> >> ~243kb of json. With all types, it grows to ~273kb. Unmask it grows to
> >> ~308kb.
> >>
> >> Could we send the full version? Eventually, we could have a "flavour":
> >> "full" argument.
> >>
> >> Another option is to compress the schema. A "full-gz" in baes64 would be 51kb.


> 
> > - At runtime, query-qmp-schema decompresses it and parses the JSON to
> > keep compatibility with existing commands, applying filtering and
> > typename substitution
> > - Add a query-qmp-schema-data, which returns the unmodified compressed
> > JSON schema blob (~35kb in base64)
> 
> If we expose QAPI schema type names externally, they become ABI.  The
> design decision not to has enabled schema refactorings time and again.
> Changing that feels like a bad idea.

Yeah the ability to change our type names has been surprisingly
useful and common, in fact because it allows more than just
type name changes. A single type exposed in QMP can map to
multiple types in QAPI, thanks to the inheritance from the
'base' keyword.  That inheritance is flattended in what we
expose in QMP.



With regards,
Daniel
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