Hi Robert,
Yes, my intention about Java records (e.g.
https://openjdk.org/jeps/395) is to leverage:
- Devise an object-oriented construct that expresses a simple
aggregation of values.
- Focus on modeling immutable data rather than extensible behavior.
- Automatically implement data-driven methods such as equals and accessors.
- Preserve long-standing Java principles such as nominal typing and
migration compatibility.
- Provide inner builder, optionally with technical validation
(Objects.NotNull, etc), for instance:
public record CatalogDAO(String id, String name, ...) {
public static final class Builder {
String id;
String name;
public Builder() {}
public Builder id(String id) {
this.id = id;
return this;
}
public Builder name(String name) {
this.name = name;
return this;
}
public CatalogDAO build() {
return new CatalogDAO(id, name);
}
}
}
NB: that's just a "raw" example :)
That could help us for the "DAO" layer, with clean isolation and data
"transport". The "conversion" from Polaris Entity to DAO could be
performed by the intermediate logic layer (e.g.
PolarisMetaStoreManager), the pure persistence layer can deal with DAO
only (e.g. PolarisStore).
Good point about immutable collections. In some projects, I "force"
the copy of a collection to ensure immutability, something like:
record NamespaceDAO(Set<String> children) {
public NamespaceDAO {
children = Set.copyOf(children);
}
}
OK, that's not super elegant :) but it does the trick ;)
Regards
JB
On Mon, Feb 17, 2025 at 5:28 PM Robert Stupp <sn...@snazy.de> wrote:
>
> Agree with JB, except I think "immutables" serves the need much better.
> Java records are okay, but do not ensure that all fields are immutable -
> especially collections. The other pro of immutables is that there are
> proper, descriptive builders - hence no need to constructors with a
> gazillion parameters.
>
> On 17.02.25 11:42, Jean-Baptiste Onofré wrote:
> > Hi Yufei
> >
> > I left comments in the PR.
> >
> > Thanks for that. That's an interesting approach but slightly different
> > to what I had in mind.
> >
> > My proposal was:
> >
> > 1. The DAOs are Java records clearly descriptive, without "storage
> > operations".
> > For instance, we can imagine:
> >
> > public record CatalogDao(String id, String name, String location, ...) {
> > ...
> > }
> >
> > public record NamespaceDao(String id, String name, String parent, ...) {}
> >
> > public record TableDao(String id, String name, ...) {}
> >
> > etc
> >
> > The advantages are:
> > - very simple and descriptive
> > - common to any backend implementation
> >
> > 2. The PolarisStore defines the DAO backend operations and mapping to
> > "internal" Polaris entities. Each persistence adapter implements the
> > PolarisStore.
> > For the persistence adapter implementer, he just has to implement the
> > DAO persistence (no need to understand other Polaris parts).
> > Each persistence adapter is in its own module (for isolation and
> > dependencies).
> >
> > During the Polaris Persistence Meeting last week, we already got
> > consensus on the approach proposed by Dennis and I. I propose to do a
> > new sync/review with Dennis.
> >
> > Regards
> > JB
> >
> > On Mon, Feb 17, 2025 at 9:40 AM Yufei Gu <flyrain...@gmail.com> wrote:
> >> Hi Folks:
> >>
> >> Here is a POC for persistence layer refactor. Please check it out and let
> >> me know what you think. Please note this is a POC, we still need a lot of
> >> effort to complete the refactor.
> >>
> >> PR: https://github.com/apache/polaris/pull/1011.
> >> Design doc:
> >> https://docs.google.com/document/d/1Vuhw5b9-6KAol2vU3HUs9FJwcgWtiVVXMYhLtGmz53s/edit?tab=t.0
> >>
> >> Experiment:
> >>
> >> - Added a DAO layer for the business entity namespace(except the read).
> >> - Integrated with existing DAO components (PolarisMetaStoreManager and
> >> PolarisMetaStoreSession).
> >> - All tests passed successfully, including a manual local run with
> >> Spark
> >> sql.
> >>
> >> Benefits:
> >>
> >> - Compatible with the existing backend(FDB), as we hide it behind the
> >> new DAO.
> >> - Adding new backends(Postgres/MongoDB) is much easier now, esp for
> >> Postgres, we could be able to use a similar model as Iceberg Jdbc
> >> catalog.
> >> - Allows gradual refactoring to remove old DAO dependencies
> >> (PolarisMetaStoreManager and PolarisMetaStoreSession).
> >> - Enables parallel development of new backend implementations.
> >>
> >> Next Steps:
> >>
> >> - Define business entities one by one to decouple them from FDB.
> >> - Create DAO interfaces for each entity to standardize operations
> >> (e.g.,
> >> CRUD, ID generation).
> >> - Expand DAO implementations to support additional backends over time.
> >>
> >>
> >>
> >>
> >> Yufei
>
> --
> Robert Stupp
> @snazy
>
