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From Niclas Hedhman <nic...@hedhman.org>
Subject ORM EntityStore
Date Sat, 06 May 2017 08:25:28 GMT

I have gotten overly angry with Hibernate on $dayjob, and decided to take a
look at what a ORM-ish implementation in Polygene would look like. And it
was easier than I expected, so...

Pretty simple,

0. One "types table" that keep tracks of all types. Content of this is
probably fully cached.

1. One type table for each MixinType (except HasIdentity)

2. One "base entity" table with the Identity, lastmodifed and so on stuff.

3. Use a different (internal) identity for the "value", which makes it easy
to fully support non-destructive updates.

4. Property->SQL on basic types, and Serialization kick in on

5. Association->SQL is simply a VARCHAR

6. Named/ManyAssociation->SQL needs an intermediate table per assoc (naming
is trouble some)

7. get() becomes a SELECT with one join per mixin type

8. new/update is bunch of INSERT (if non-destructive is used) SQL
statement, one for each mixin type plus an UPDATE for "base entity".

9.  Named/ManyAssociations will also be an INSERT with many values.

10. JOOQ is awfully helpful in making this, and I am trying to modularize
it so that people can customize it if needed, at Composite Methods level,
either by Concerns or overriding Mixin methods.

11. IF destructive mode is wanted, I suggest that DELETE statements are
issued to remove old stuff, which makes both modes semantically identical,
and not a big deal if something is accidentally not removed.

And that is pretty much it. Fairly straight forward, and a far cry from the
complexity of Hibernate, guessing what it does and why.

NOTE, this is only for "Java Model drives SQL model", but in an
enterprise-friendly way. I hope that this can be a big "adoption driver".


Niclas Hedhman, Software Developer
http://polygene.apache.org - New Energy for Java

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