cypher 2.0 : using label based index to search a set of nodes

问题

I have users and groups they belong to. I have an index n:Group(name)

I want to search for all users belong to a set of groups : ["gr1","gr2","gr3"]

which other groups they belong to.

so I have the following query: Query :

MATCH (gr:Group) <--(us:User)--(gr2:Group)
WHERE gr.name in ["gr1","gr2"]
return distinct gr2

The thing here, is that I think that cypher don't use the index because the query is to slow.

I have 2k nodes, 50k relationships. The following query takes between 200 to 700 ms (depending on cache):

MATCH (gr:Group) <--(us:User)--(gr2:Group)
WHERE gr.name = "gr1"
return distinct gr2

However, the following query, takes between 2 to 6 seconds!

MATCH (gr:Group) <--(us:User)--(gr2:Group)
WHERE gr.name in ["gr1"]
return distinct gr2

When I'm trying to do :

MATCH (gr:Group) <--(us:User)--(gr2:Group)
using index gr:Group(name)
WHERE gr.name in ["gr1"]
return distinct gr2

I get the following error:

Cannot use index hint in this context. The label and property comparison must be specified on a non-optional node
Label: `Group`
Property name: `name`

(with "=" instead of "in" I get no error)

I'm using neo4j enterprise 2.0.1 . The test results are from running on the neo4j browser .

回答1:

The index is referred either when you specify the attribs in the pattern as in (gr:Group {name: "gr1"}) or you call WHERE gr.name = "gr1". In your case where multiple attrib values are possible you can use OR clause.

MATCH (gr:Group) <--(us:User)--(gr2:Group)
WHERE gr.name="gr1" OR gr.name="gr2"
return distinct gr2

来源：https://stackoverflow.com/questions/21617625/cypher-2-0-using-label-based-index-to-search-a-set-of-nodes