问题标签 [titan]

我已经在集群模式下配置了 Cassandra-1.2.2。但是在使用我的 cassandra 配置启动 Titan 时，它显示以下异常

请帮忙看看是什么问题？

我正在做一个项目，在该项目中我使用 Neo4j 构建社交网络图。但是我发现 Neo4j 占用了大量的内存空间。对于大约 35k 个节点和 30k 个边，它占用了超过 5GB 的磁盘空间。我很担心，如果我想创建一个包含数亿用户和相同范围边的图形，它会占用很多我无法管理的空间。

所以在寻找替代的graphDB时，我发现了“泰坦”。在继续尝试之前，我想知道，是否有人可以比较这两个数据库（neo4j 和 titan）的（1）内存使用情况，（2）顶点和边属性的查询响应速度， (3) 可用性、安全性和任何其他附加重要参数。

谢谢。

我正在通过 gremlin shell 连接到 hbase 和 cassandra 并创建图形，但是当我停止 shell 并重新启动 shell 时，图形不会持续存在，谁能告诉我如何将图形从数据库加载到 shell 以查询它.

我尝试使用以下函数加载图表，但出现以下错误。

谢谢

I'm pretty new to the NoSQL scene. I'm trying to understand the capabilities and differences between different graph databases. My understanding is that Orient and Arango use documents as vertices (and edges too, right?). I know that in Titan and Neo that vertices and edges may have properties and that these properties are key:value pairs. It makes sense to me that you might limit the values to primitives (though I don't know that this is strictly the case). I'm wondering just what you can have as a value. Can your value be an array of primitives? Can it be another hash? etc. If the values are rather unrestricted then I wonder how Titan or Neo really differ from Orient and Arango with respect to the ways in which you can structure your data.

edit: People are asking about my use case -- My company has developed a toolchain that creates a working applications (GUI and database) from UML models...in seconds. We use these tools to model a number of different domains (whatever a customer comes to use with) and develop solutions for them. Right now the tooling uses an ORDBM. This has its drawbacks, some of which are showstoppers if my thoughts on how we should evolve mean anything. I'm trying to do my due diligence in exploring alternatives. I can accept that nothing is perfect and that whatever we choose won't be the optimal choice for every customer's use case. Because of the automation involved we may not necessarily take advantage of every feature a particular db offers either on a case by case basis. So, I suppose I'm trying to decide which db would be a good fit for our tooling. (Note also that the original question posed here is just one of many deciding factors.) Oh yea, FWIW, we do Ruby. We could shift to maybe Python or Groovy or something else but it would be far from trivial to do so.

我正在 Windows 7 上使用 Titan Server（使用 Cassandra）v0.3.1，并看到一些关于写入图表的不一致行为。出于某种原因，新节点在提交事务后似乎“消失”了。我认为其中涉及某种缓存/延迟写入，但不确定 Titan 在幕后做了什么。

您对为什么节点在提交时似乎消失有任何想法吗？

--

以下是在 Gremlin shell 中运行的一系列命令：

显示到目前为止我添加到图表中的两个节点：

现在添加一个节点：

新节点出现在图中：

现在，提交事务：

...并且新节点消失了：

I am using Titan Server (Cassandra) v 0.3.1. I'd like to create an index on a vertex key/property that I have already started to use. However, in their documentation, Titan explains that:

To index vertices by key, the respective key index must be created before the key is first used in a vertex property.

If I try to create an index on a field that already exists, I see an error as expected:

However, even if I try to clear out the graph by removing all vertices & edges, I see the same error:

So it seems that my_key persists in the underlying data store even after all of the graph elements are removed. This is consistent with the docs (even though elements have been deleted the property has already been 'first used'), but seemed worth a shot.

My next step is going to be to re-create a new Cassandra data store altogether, but I'm wondering if there is a better option.

What is the easiest way to create an index on a field that has already been used in Titan?

使用 Titan w/Cassandra v 0.3.1，我通过Titan 文档createKeyIndex中的描述创建了一个顶点键索引。

我现在在图中有 appx 50k 个节点和 186k 条边，我发现使用my_key. 此查询大约需要 5 秒才能运行：

而使用索引 ID 只需不到 1 秒：

my_key没有唯一的约束（我不想），但我想知道是什么导致了这种性能差异。如何提高查找非唯一索引顶点键的性能？

谁能提供或指出 Neo4j 和 Titan 之间的一个很好的比较？我能看到的一件事是在规模方面——Titan 是横向扩展的，需要像 cassandra 这样的底层可扩展数据存储。Neo4j 仅适用于 HA，并且有自己的嵌入式数据库。还有其他优点和缺点吗？任何特定的用例。（泰坦目前是否在任何地方使用？）

我还有以下链接：http : //architects.dzone.com/articles/16-graph-databases-compared，它对图形数据库进行了客观比较，但对 Neo4j 和 Titan 之间的优缺点并没有太多了解。

有人知道在 Titan 图上执行模块化（社区检测）算法的现有方法吗？我正在寻找类似 Gephi 的模块化功能的东西，我相信它使用https://sites.google.com/site/findcommunities/。

Gephi Toolkit 似乎提供了该算法的实现，这可能是一种选择。有没有人尝试过通过 Blueprints 插件使用 Gephi Toolkit 加载 Titan 图？

一个要求是这一切都需要自动和就地发生。这意味着，我无法将图形导出为另一种格式，也无法使用 Gephi 桌面应用程序之类的工具手动运行模块化检测。

我想使用带有 Cassandra 的 Titan 作为图形数据库（使用 Faunus 作为框架）。我在哪里可以获得 Faunus 或 Gremlin 的示例代码？我想查询 Graüh DB 上的 pagerank 算法？