Gremlin查询最后一个值的groupcount [英] Gremlin query for groupcount of last value

问题描述

我有一个带有两套顶点的泰坦图，一套用于UserID，另一套用于Products.购买产品时，UserID和产品顶点之间的边缘包含日期".我正在寻找一个gremlin查询，该查询可以按上次购买的产品给我一组用户ID

I have a titan graph with two sets of vertices, one for UserID and another for Products. The edges between the UserID and Product vertices contain the "Dates" when products were purchased. I am looking for a gremlin query that can give me a groupcount of userids by the last product purchased

例如，如果有如下数据

UserID,Date,Product
A,2016-01-01,'Razor'
A,2016-01-02,'Toothpaste'
B,2016-02-01,'Toothpaste'
B,2016-02-02,'Razor'
C,2016-01-04,'Toothpaste'

我正在寻找类似下面的输出

I am looking for an output like below

Product, Count
'Toothpaste',2
'Razor',1

非常感谢您的帮助.

推荐答案

以下查询可在OLTP和OLAP中使用，并且不会触及过多的顶点:

The following query works in OLTP and OLAP and doesn't touch more vertices than necessary:

g.V().hasLabel("User").
  local(outE("purchased").order().by("date", decr).limit(1)).inV().
  groupCount().by("name")

此外，当您在date上创建顶点中心索引时，Titan可以完美地优化此查询.

Furthermore this query can be perfectly optimized by Titan, when you create a vertex centric index on date.

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