https://github.com/julianhyde/linq4j

A port of LINQ (Language-Integrated Query) to Java
https://github.com/julianhyde/linq4j

Last synced: 8 months ago
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A port of LINQ (Language-Integrated Query) to Java

• Host: GitHub
• URL: https://github.com/julianhyde/linq4j
• Owner: julianhyde
• License: apache-2.0
• Created: 2012-04-20T03:40:33.000Z (over 13 years ago)
• Default Branch: master
• Last Pushed: 2023-12-17T03:40:39.000Z (almost 2 years ago)
• Last Synced: 2025-03-29T05:05:52.998Z (8 months ago)
• Language: Java
• Size: 2.16 MB
• Stars: 374
• Watchers: 40
• Forks: 109
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • Changelog: HISTORY.md
  • License: LICENSE

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README

          
[![Build Status](https://travis-ci.org/julianhyde/linq4j.png)](https://travis-ci.org/julianhyde/linq4j)

linq4j

======

A port of LINQ (Language-Integrated Query) to Java.

Download

========

    $ git clone git://github.com/julianhyde/linq4j.git linq4j

Build and test

==============

    $ mvn package

Backlog

=======

If you would like to contribute, here are some of the tasks we have planned.

Please let us know if you are starting one.

* Implement and test the methods allowing queries on Enumerables. The methods

  are specified in ExtendedEnumerable, DefaultEnumerable calls the

  implementations in Extensions. We'll do these in tranches. Each time you

  implement a method, add a test similar to Linq4jTest.testWhere.

  Try to refactor out some helper (named inner) classes, rather than creating

  2 or 3 anonymous classes per method.

* Third tranche: implement groupBy for Enumerable.

* Fourth tranche: implement any, all, aggregate, sum, min, max, average

  for Enumerable.

* Sixth tranche: implement union, intersect, except, distinct methods

  for Enumerable.

* Seventh tranche: first, last, defaultIfEmpty, elementAtOrDefault,

  firstOrDefault, lastOrDefault for Enumerable. May need to add a class

  parameter so that we can generate the right default value.

* Eighth tranche: implement orderBy, reverse for Enumerable.

* Ninth tranche: implement methods that require EqualityComparer.

* Last tranche: all remaining methods for Enumerable.

* Parser support. Either modify a Java parser (e.g. OpenJDK), or write a

  pre-processor. Generate Java code that includes expression trees.

* Port Enumerable and Queryable to Scala. Change classes (in particular,

  collections and function types) so that user code is looks like concise,

  native Scala. Share as much of the back-end as possible with linq4j, but

  don't compromise the Scala look-and-feel of the front-end. Use adapters

  (and sacrifice a bit of performance) if it helps.

* Write a simple LINQ-to-SQL provider. This would generate SQL and get data

  from JDBC. It's a prototype, demonstrating that we can connect the dots.

  Plan to throw it away.

* In the prototype LINQ-to-SQL provider, write a simple rule to recognize a

  select list and where clause and push them down to SQL.

* Test Scala front-end against LINQ-to-SQL provider.

* A better provider using a planner framework.

* JDBC driver on top of linq4j (not necessarily on top of the

  Queryable/Expression object model; more likely on the query model that this

  translates to).

* Use planner framework to build back-ends to non-SQL data sources (e.g.

  MongoDB, Hadoop, text files).

Already implemented

===================

Methods on Enumerable:

* select, selectMany, where, groupJoin, join;

* count, longCount;

* cast, ofType;

* toMap, toLookup, skip, skipWhile, take, takeWhile.

Methods on Queryable:

* where, whereN

* skip, skipWhile, skipWhileN, take, takeWhile, takeWhileN.

(Except methods that involve EqualityComparer.)

More information

================

* License: Apache License, Version 2.0.

* Author: Julian Hyde

* Blog: http://julianhyde.blogspot.com

* Project page: http://www.hydromatic.net/linq4j

* Source code: http://github.com/julianhyde/linq4j

* Developers list: http://groups.google.com/group/linq4j-dev

* Release notes and history