Gremlin图查询将始终在其自己的地址空间中执行操作吗? [英] will Gremlin graph queries always perform operations in it's own address space?
问题描述
诚然，我的大多数数据库经验是关系型的.该领域的宗旨之一是避免在网络上移动数据.这可以通过使用类似的东西来体现:
admittedly, most of my database experience is relational. one of the tenets in that space is to avoid moving data over the network. this manifests by using something like:
select * from person order by last_name limit 10
大概会在数据库引擎中进行排序和限制，而不是使用类似的方法:
which will presumably order and limit within the database engine vs using something like:
select * from person
，然后订购并排在客户的前10名，如果有100万人的记录，可能会造成灾难性的后果.
and subsequently ordering and taking the top 10 at the client which could have disastrous effects if there are a million person records.
因此，如果我做类似的事情，请使用Gremlin(来自Groovy):
so, with Gremlin (from Groovy), if i do something like:
g.V().has('@class', 'Person').order{println('!'); it.a.last_name <=> it.b.last_name}[0..9]
我看到打印了!，所以我假设这会将所有Person记录都放在订单和限制步骤之前的客户地址空间中，这不是预期的效果.
i am seeing the ! printed, so i am assuming that this bringing all Person records into the address space of my client prior to the order and limit steps which is not the desired effect.
我完全在数据库引擎中处理查询的选项是否因产品而异(例如，针对orient-db可能以SQL风格提交查询)，或者我缺少Gremlin的某些信息?
do my options for processing queries entirely in the database engine become product specific (e.g. for orient-db perhaps submit the query in their flavor of SQL), or is there something about Gremlin that i am missing?
推荐答案
如果希望实现者的查询优化器加入，则需要使用尽可能多的Gremlin步骤，并避免对图形进行纯Groovy/内存中处理遍历.
If you want the implementer's query optimizer to kick in, you need to use as many Gremlin steps as possible and avoid pure Groovy/in-memory processing of your graph traversals.
您最有可能正在寻找类似这样的东西(从TinkerPop v3.2.0开始):
You're most likely looking for something like this (as of TinkerPop v3.2.0):
g.V().has('@class', 'Person').order().by('last_name', incr).limit(10)
如果您发现自己使用了lambda，那么通常可以通过纯Gremlin步骤完成此操作.偏爱Gremlin越过lambda.
If you find yourself using lambdas, chances are often high that this could be done with pure Gremlin steps. Favor Gremlin steps over lambdas.
请参阅TinkerPop v3.2.0文档:
See TinkerPop v3.2.0 documentation:
- Order By step
- Limit step
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