Add Fluent API for Query Functions in Jakarta NoSQL (e.g., LEFT, UPPER, ABS, etc.)

[otaviojava]

The Jakarta Query specification defines support for function expressions such as ABS(), LENGTH(), LOWER(), UPPER(), LEFT(), and RIGHT().

Currently, Jakarta NoSQL does not expose these functions in its fluent query API. This proposal introduces a structured way to represent and use these functions in queries using the fluent API.

💡 Motivation

Adding function support at the fluent level will:

• Allow users to express richer queries without string-based parsing
• Improve type safety
• Increase developer productivity
• Support use cases already defined in Jakarta Query

This allows Jakarta NoSQL to integrate more deeply with the Jakarta Query grammar while providing an intuitive developer experience.

✅ Example Usage

template.select(Word.class)
        .where(Function.left("term", 2))
        .eq("Ja")
        .result();

template.select(Word.class)
        .where(Function.upper("meaning"))
        .eq("COFFEE")
        .result();

template.select(Product.class)
        .where(Function.abs("price"))
        .gt(10)
        .result();

---

📌 Tasks

• Design the Function API class (e.g., static factory methods)

• Integrate Function into WhereClause expressions

• Update the Template.select() fluent chain to accept function expressions

• Add examples and usage documentation in the specification

• Implement TCK tests for:

  • LEFT()
  • RIGHT()
  • UPPER()
  • LOWER()
  • LENGTH()
  • ABS()

[otaviojava]

I am reviewing these functions to ensure support for both the fluent API and Jakarta Query. However, in practice, most NoSQL databases do not provide native support for such scalar functions. Their availability is generally limited to NoSQL databases that expose an SQL-compatible query layer (such as Couchbase or Oracle NoSQL) and to some graph databases (such as Neo4j via Cypher).

Database (JNoSQL driver)	ABS	LENGTH	LOWER	UPPER	LEFT/RIGHT
MongoDB	❌	✅	✅	✅	✅
Couchbase (N1QL)	✅	✅	✅	✅	✅
CouchDB	❌	❌	❌	❌	❌
Cassandra / ScyllaDB	❌	❌	❌	❌	❌
Redis	❌	⚠	❌	❌	❌
DynamoDB	❌	❌	❌	❌	❌
TinkerPop (Gremlin)	⚠	⚠	⚠	⚠	⚠
Oracle NoSQL	✅	✅	✅	✅	✅
Neo4j (Cypher)	❌	✅	✅	✅	✅

[otaviojava]

@dearrudam, give this scenario, I will skip this feature to Jakarta NoSQL, what do you think?

[dearrudam]

Yeah, I agree with you... let's see that later.

[omatheusmesmo]

Hi @otaviojava ,

This issue is still open despite being closed on the Eclipse JNoSQL project.

[otaviojava]

@omatheusmesmo, we need to do it, even if not on this version.
Eventually, we need to release this on to integrate with Jakarta Data and Jakarta Query.