[GROOVY-8258] [GEP] Create a LINQ-like DSL (basic cases)

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-2
• Assignee: Daniel Sun
• Reporter: Daniel Sun
• Created: 16/Jul/17 16:22
• Updated: 07/Dec/20 22:09
• Resolved: 05/Nov/20 21:43

Description

Ⅰ. Introduction

GINQ DSL is an alternative solution of GINQ, it is a simplified version of GINQ(GROOVY-9159) and will be implemented as a module "groovy-ginq".

GINQ DSL is wrapped with:

GQ {
   // GINQ code
}

NOTE:

• The simplest GINQ MUST consist of ONE from clause and ONE select clause, which looks like:

from n in [1, 2, 3]
select n

• Currently supports the following clauses:

       ginq
       |__ from
       |__ [innerjoin/leftjoin/rightjoin/fulljoin/crossjoin]*
       |   |__ on
       |__ [where]
       |__ [groupby]
       |   |__ [having]
       |__ [orderby]
       |__ [limit]
       |__ select
   
(Note: [ ] means optional)

Ⅱ. Sample code related to GROOVY-9159

1. Filtering

1.1

from p in persons
where p.age > 15 && p.age <= 35
select p.name

1.2

from p in persons
where p.age > 15 && p.age <= 35
select p

1.3

from t in numbers 
where t <= 2
select t

2. Joining

2.1

from p in persons
innerjoin c in cities on p.city.name == c.name // putting `on` clause in the same line with `innerjoin` is recommended code style
select p.name, c.name

2.2

from p in persons
innerjoin c in cities on p.city == c
select p.name

2.3

from p in persons
leftjoin c in cities on p.city.name == c.name //  same with left outer join
select p.name, c.name

2.4

from p in persons
rightjoin c in cities on p.city.name == c.name //  same with right outer join
select p.name, c.name

3. Projection

3.1

from p in persons
select p.name

3.2

from p in persons
select p.name, p.age

3.3

from p in persons
select [name: p.name, age: p.age]

3.4

from p in persons
select new Person(name: p.name, age: p.age)

3.5

from p in persons
select p

4. Grouping

4.1

from p in persons
groupby p.gender
select p.gender, max(p.age)

5. Having

5.1

from p in persons
groupby p.gender
having p.gender == 'Male'
select p.gender, max(p.age)

6. Sorting

6.1

from p in persons
orderby p.age
select p.name

6.2

from p in persons
orderby p.age in desc // "`in` order" means sorting
select p.name

6.3

from p in persons
orderby p.age in desc, p.name in asc // asc is optional
select p.name

7. Pagination

7.1

from n in numbers
limit 2, 5
select n

7.2

from n in numbers
limit 5
select n

8. Nested Queries

8.1

from v in (
    from n in numbers
    where n <= 5
    select n
)
limit 2, 5
select v

Advanced cases could be found at GROOVY-9806

Issue Links

• is cloned by: GROOVY-9806 [GEP] Create a LINQ-like DSL (advanced cases)
• is related to: GROOVY-9159 [GEP] Support LINQ, aka GINQ