Greed-Loading
Greed-Loading
Navigation Properties - ManyToOne
ManyToOne navigation properties are loaded by ToList(includeNestedMembers: false), parameter description:
false: Return the navigation data of Level 2 Join (default);
true: Return the navigation data of all levels of depth Join (unused navigation data will not be returned).
Select<Tag>().Include(a => a.Parent.Parent).ToList(true);
Select<Tag>().Where(a => a.Parent.Parent.Name == "1").ToList(true);
//Write in this way, no need to mark Join,
//it will be automatically processed into LeftJoin when parsing the expression
Navigation Properties - OneToMany/ManyToMany
IncludeMany greedily loads the navigation properties of the collection. In fact, it is queried twice, and data is assembled after ToList.
Select<Tag>().IncludeMany(a => a.Songs).ToList();
IncludeMany has a second parameter, which can be modified before the second query.
Select<Tag>().IncludeMany(a => a.Songs,
then => then.Where(song => song.User == "admin")).ToList();
In fact, in Then, you can continue to use Include/IncludeMany. As long as you like it, it’s okay to go down 100 levels.
Mutations
It can also be greedily loaded without configuring the navigation relationship.
Select<Tag>().IncludeMany(a => a.TestManys.Where(b => b.TagId == a.Id));
Only query the first few pieces of data in each sub-collection to avoid poor IO performance caused by loading all data like EfCore (for example, there are 2000 comments under a product).
Select<Tag>().IncludeMany(a => a.TestManys.Take(10));
The sub-collection returns a part of the fields to avoid the problem of too many fields.
Select<Tag>().IncludeMany(a => a.TestManys.Select(b => new TestMany { Title = b.Title ... }));
IncludeMany Extensions
When the main data already exists in the memory, how to load the sub-data? So we added the List<T> extension method, the example is as follows:
new List<Song>(new[] { song1, song2, song3 })
.IncludeMany(fsql, a => a.Tags);
new List<Song>(new[] { song1, song2, song3 })
.IncludeByPropertyName(
orm: fsql,
property: "Tags",
where: "ParentId=Code",
take: 5,
select: "id,name"
);
//v3.2.605+
Comparison of the Two Ways of IncludeMany
Way 1: IncludeMany extensions
var list111 = fsql.Select<SysModule>()
.Page(1, 10)
.ToList(a => new { Id = a.Id }) //Query data id
.Select(a => new SysModule { Id = a.Id }).ToList() //Memory operation
.IncludeMany(fsql, a => a.Permissions, then => then.Include(a => a.Button));
SELECT a."Id" as1
FROM "SysModule" a
limit 0,10
SELECT a."Id", a."SysModuleId", a."SysModuleButtonId", a."Status",
a__Button."Id" as5, a__Button."Name", a__Button."EventName", a__Button."EnCode", a__Button."Icon", a__Button."Sort", a__Button."CreateTime"
FROM "SysModulePermission" a
LEFT JOIN "SysModuleButton" a__Button ON a__Button."Id" = a."SysModuleButtonId"
WHERE ((a."SysModuleId") in ('menu1','menu2'))
Way 2: Directly IncludeMany + ToList
var list222 = fsql.Select<SysModule>()
.IncludeMany(m => m.Permissions, then => then.Include(a => a.Button))
.Page(1, 10)
.ToList();
SELECT a."Id", a."ParentId", a."Name", a."Icon", a."UrlAddress", a."IsShow", a."Sort", a."Description", a."CreateTime"
FROM "SysModule" a
limit 0,10
SELECT a."Id", a."SysModuleId", a."SysModuleButtonId", a."Status",
a__Button."Id" as5, a__Button."Name", a__Button."EventName", a__Button."EnCode", a__Button."Icon", a__Button."Sort", a__Button."CreateTime"
FROM "SysModulePermission" a
LEFT JOIN "SysModuleButton" a__Button ON a__Button."Id" = a."SysModuleButtonId"
WHERE ((a."SysModuleId") in ('menu1','menu2'))
Case: Query Vod table, 10 data for each of category 1, category 2, and category 3
class Vod {
public Guid Id { get; set; }
public int TypeId { get; set; }
}
//Define a temporary class, it can also be a DTO
class Dto {
public int TypeId { get; set; }
public List<Vod> Vods { get; set; }
}
var dto = new [] { 1,2,3 }.Select(a => new Dto { TypeId = a }).ToList();
dto.IncludeMany(fsql, d => d.Vods.Take(10).Where(vod => vod.TypeId == d.TypeId));
//After execution, each element.Vods of DTO will only have 10 records