Slowly Changing Dimension (SCD) Example

This example shows using a very simplistic SCD Type 2 persistence using JPA. This demonstrates:

Typical 'Person' entity:
- By name,
- By name at a point-in-time (instant),
- Audit trail,
- All latest vales,
- All audit trail (rarely used, but useful example non-the-less),
Time-series:
- Raw,
- Tumbling windows with variable alignment period and start and end dates using either date or date and time.

ℹ️ For simplicity sake, this doesn't use start/end dates, it just uses a inserted value as part of the key.

ℹ️ Returned time-series data windows are [start, end) meaning start is inclusive and end is exclusive as this tends to look cleaner.

Notes:

It seems EclipseLink refuses to compile with Java 16. It's due to a really old version of ASM and that's not going to be updated until 3.0.1 (aka Jakarta). Workaround is to use bump to just org.eclipse.persistence:org.eclipse.persistence.asm:3.0.1.
Regardless of what H2 documentation states, it doesn't work with java.time.Instant (or it could be PIBCAK!). So I had to create a attribute converter to do this,
E-Tag is generated from the hashcode of the key of an entity. For a collection of entities it gets all the keys and creates it from them. The potential for collision is probably not wonderful, but for the purposes of this it's adequate',
If you want to view your data, go to localhost:8082 and use JDBC URL jdbc:h2:mem:app,
Some of the queries use correlated subqueries, which can be a concern but this can be mitigated with indexes on the correlation criteria and some DBs can rewrite them.

To run pgAdmin:

docker run -p 8082:80 `
	-e 'PGADMIN_DEFAULT_EMAIL=admin@acme.com' `
	-e 'PGADMIN_DEFAULT_PASSWORD=pwd' `
	--rm `
	-d `
	dpage/pgadmin4

When the application is running locally you can then connect to your database using: host.docker.internal:<port>

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