已知深度和边查询效率

Question

我的数据是这样的：

a ---> b ---> c

a、b、c为顶点，a只有一个，b-s、c-s有多个（树形结构）。

我的 a ---> b 边是一个 class（我们称它为 ab class），而 b ---> c 边是另一个（bc class).

我需要一个查询，给定 a 的名称，生成 x 个 c-s。

到目前为止，我发现这行得通：

select expand(set(out("ab").out("bc"))) from a where name='aName' limit x

问题：

可以改进这个查询吗？
如何只select，例如c-s的名称，而不是整个记录？

感谢您的帮助！

Answer 1

我相信只有在 A.name 属性上定义 index 才能改进查询。

关于你的第二个问题：

create class A extends V
create class B extends V
create class C extends V    

create class AB extends E
create class BC extends E

create vertex A set name = 'aName'
create vertex B set name = 'bName0'
create vertex B set name = 'bName1'
create vertex C set name = 'cName0'
create vertex C set name = 'cName1'
create vertex C set name = 'cName2'
create vertex C set name = 'cName3'    

create edge AB from (select from A where name = 'aName') to (select from B where name = 'bName0')
create edge AB from (select from A where name = 'aName') to (select from B where name = 'bName1')
create edge BC from (select from B where name = 'bName0') to (select from C where name = 'cName0')
create edge BC from (select from B where name = 'bName0') to (select from C where name = 'cName2')
create edge BC from (select from B where name = 'bName1') to (select from C where name = 'cName1')
create edge BC from (select from B where name = 'bName1') to (select from C where name = 'cName3')

这些查询可能对您有所帮助：

select from (select expand(out("AB").out("BC").include('name')) from A where name = 'aName') limit 3
// or
select name from (select expand(out("AB").out("BC")) from A where name = 'aName') limit 3

已知深度和边查询效率

Known depth and edges query efficency

orientdb