Not that I have a need for it, but how pluggable is the JDBC connector
part of Cayenne? That is, could the backend be easily exchanged for json
or some other data source, even if only in a read-only way? Could also
be an interesting way to demonstrate Modeler to new users...
Ari
On 30/12/21 1:24am, Andrus Adamchik wrote:
An idea of in-memory query evaluation fits Cayenne to a degree. Though it is limited to what we
already do with in-memory expression-based filtering and sorting. A more fancy data transformation
(even a simple "toUpperCase" from your example) runs against the basic ORM philosophy
("toUpperCase" would be a property that does not directly correspond to a value in DB).
I solved it for myself by splitting use cases in two groups:
1. "Data as object graph" where Cayenne is appropriate (most cases)
2. "Data as data" with extra "plasticity" of changing any piece of data on the
fly
For #2 sometimes I'd use Cayenne (e.g. column queries, SQLSelect), but most
often I'd go with DFLib. The main data object in it is a DataFrame (essentially
a dynamic in-memory table). DataFrame is not tied to a specific object
structure, and can be dynamically transformed (columns added, removed, changed,
rows filtered, joins, unions, etc.). DFLib can do what GINQ can and more, but
it intentionally sacrifices a familiar OO representation to support arbitrary
intermediate data states and frictionless mapping-free persistence.
DataFrame df = Csv.load("my.csv")
.selectColumns("id", "price")
.selectRows($decimal("price").gt(100.));
Jdbc.connector(dataSource)
.tableSaver("db_table")
.save(df);
Andrus
On Dec 28, 2021, at 11:50 PM, Aristedes Maniatis <a...@ish.com.au.INVALID>
wrote:
I came across this really interesting new feature in groovy 4 today...
class Person {
String name
int age
Person(String name, int age) {
this.name = name
this.age = age
}
}
def persons1 = [new Person('Daniel', 35), new Person('Linda', 21),
new Person('Peter', 30)]
def persons2 = [new Person('Jack', 35), new Person('Rose', 21), new
Person('Smith', 30)]
def output = GQ {
from p1 in persons1
innerjoin p2 in persons2 on p1.age == p2.age
select p1.name.toUpperCase(), p2.name.toUpperCase()
}
assert [['DANIEL', 'JACK'], ['LINDA', 'ROSE'], ['PETER', 'SMITH']]
== output.toList()
So GQ invokes this sql-like query language for Java/groovy objects.
Not suggesting it is useful for Cayenne, but interesting nevertheless.
Ari
docs:https://github.com/apache/groovy/blob/master/subprojects/groovy-ginq/src/spec/doc/ginq-userguide.adoc
examples:
https://github.com/apache/groovy/blob/master/subprojects/groovy-ginq/src/spec/test/org/apache/groovy/ginq/GinqTest.groovy
src:
https://github.com/apache/groovy/tree/master/subprojects/groovy-ginq/src/main/groovy/org/apache/groovy/ginq
