限制gremlin查询中group().by()中的项目数 [英] Limit number of items in group().by() in gremlin query

问题描述

我正在尝试运行 gremlin查询，该查询将某个标签的顶点分为几个组，通过某个字段(假设它是"displayName")，并限制 n 的组数，每个组中的项目数也 n .

I am trying to run a gremlin query which groups vertices of a certain label into several groups by a certain field (assume it is 'displayName') and limit the number of groups to n and the number of items in each group also to n.

有没有办法实现这一目标?

由于group().by()返回该项目的列表，因此我尝试使用unfold()，然后对内部项目应用限制.我设法限制了返回的组的数量，但无法限制每个组中的项目数.

Since group().by() returns a list of the item, I tried using unfold() and then applying limit on the inner items. I managed to limit the number of groups that are returned, but couldn't limit the number of items in each group.

这是我用来限制组数的查询:

Here's the query I used to limit the number of groups:

g.V().hasLabel('customLabel').group().by('displayName').unfold().limit(n)

g.V().hasLabel('customLabel').group().by('displayName').unfold().limit(n)

// Expected result:(if n == 2)
[
 {
  "displayName1": [
   { // item 1 in first group
   },
   { // item 2 in first group
   }
  ]
 },
 {
  "displayName2": [
   { // item 1 in second group
   },
   { // item 2 in second group
   }
  ]
 }
]

// Actual result: (when n == 2)
[
 {
  "displayName1": [
   { // item 1 in first group
   },
   { // item 2 in first group
   },
   ... // all the items are included in the result
  ]
 },
 {
  "displayName2": [
    { // item 1 in second group
    },
    { // item 2 in second group
    },
    ... // all the items are included in the result
  ]
 }
]

当前，通过上述查询，我只有2个组"displayName1"和"displayName2"，但每个组都包含所有项，而不仅仅是预期的2种.

Currently, with the query above, I get only 2 groups "displayName1" and "displayName2", but each one contains all the items in it and not only 2 as expected.

推荐答案

如果要限制答案，可以通过定义组中每个键的值来实现:

If you want to limit the answer you can do it by defining the values for each key in the group:

g.V().hasLabel('customLabel')
       .group()
       .by('displayName')
       .by(identity().limit(n).fold())
        .unfold().limit(n)

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