Where statement on an indexed property takes too much time - neo4j

Question

I have a cypher query as follows:
MATCH (u:User {uid:"984172414"})-[ru:EB]->
(c:Co)<-[rf:EB]-(f:User)-[rc :EB]->(cc:Co)
WHERE (cc.uid in ["84161623"]) AND (rc.from IS NOT NULL AND rc.to IS NULL) AND
((
ru.from IS NOT NULL AND
ru.to IS NOT NULL AND
(
(rf.from <= ru.to) OR
(ru.from <= rf.to)
)
) OR (
ru.from IS NOT NULL AND
ru.to IS NULL AND
(
(ru.from <= rf.to) OR
(rf.from IS NOT NULL AND rf.to IS NULL)
)
) OR (
ru.from IS NULL AND
ru.to IS NOT NULL AND
(
(rf.from <= ru.to) OR
(rf.from IS NULL AND rf.to IS NOT NULL)
)
))
RETURN cc.name as coname,
f.name as fname,
cc.uid as cuid,
f.uid as fuid,
labels(f) as flabels,
null as version
LIMIT 20
This takes about 16192 ms to resolve. I have an index on co.uid but seems like it's not working. If I remove the check cc.uid in ["84161623"] and run the following query:
MATCH (u:User {uid:"984172414"})-[ru:EB]->
(c:Co)<-[rf:EB]-(f:User)-[rc :EB]->(cc:Co)
WHERE (rc.from IS NOT NULL AND rc.to IS NULL) AND
((
ru.from IS NOT NULL AND
ru.to IS NOT NULL AND
(
(rf.from <= ru.to) OR
(ru.from <= rf.to)
)
) OR (
ru.from IS NOT NULL AND
ru.to IS NULL AND
(
(ru.from <= rf.to) OR
(rf.from IS NOT NULL AND rf.to IS NULL)
)
) OR (
ru.from IS NULL AND
ru.to IS NOT NULL AND
(
(rf.from <= ru.to) OR
(rf.from IS NULL AND rf.to IS NOT NULL)
)
))
RETURN cc.name as coname,
f.name as fname,
cc.uid as cuid,
f.uid as fuid,
labels(f) as flabels,
null as version
LIMIT 20
The query resolves in only 347 ms. I can't figure out what is wrong with the (cc.uid in ["84161623"]) statement and why does adding this to the query takes 16 seconds to resolve when I already have an index on the uid. Any help will be appreciated.
update
As suggested by #cybersam I tried making the use of USING INDEX but that results in the following error:
Cannot use index hint in this context. Index hints require using an equality comparison or IN condition in WHERE (either directly or as part of a top-level AND). The comparison cannot be between two property values. Note that the label and property comparison must be specified on a non-optional node

Answer 1

Try using a USING INDEX clause to provide a hint to use that index. The Cypher processing code does not always automatically generate the most efficient code.
For example, put this between the MATCH and WHERE clauses:
USING INDEX cc:Co(uuid)
You may also need to use additional USING INDEX clauses if there are other indices. Note, however, that neo4j can not use indices in all situations; and, even if it is possible, the resulting query could theoretically be slower due to other resulting changes to the query. So, take a look at the resulting profile and test the result to make sure you are happy with it.

Answer 2

Sounds like you may need to do some sanity checking.
First of all, is :Co.uid an int or a string? It looks like you're addressing it as if it's a string, yet the values themselves look numeric. If it's an int, you can get rid of the quotes.
Same with :User.uid.
If you've been comparing ints to strings all this time, try fixing that first to see if it solves the problem. If not, you'll want to start profiling and figuring out if/when the query isn't using your index.
Next, try simplifying and profiling the query to see if the indices are actually being used:
PROFILE MATCH (u:User {uid:"984172414"}), (cc:Co)
WHERE (cc.uid in ["84161623"])
RETURN u, cc
If they're both using NodeIndexSeek or NodeUniqueIndexSeek, and if the db hits seem reasonable, you might expand out to your entire path and continue profiling. However, it's worth checking for a performance improvement if you match on the start and end nodes first, like above, then try to do your additional pattern matching. For example:
PROFILE MATCH (u:User {uid:"984172414"}), (cc:Co)
WHERE (cc.uid in ["84161623"])
WITH u, cc
MATCH (u)-[ru:EB]->(c:Co)<-[rf:EB]-(f:User)-[rc :EB]->(cc)
WHERE (rc.from IS NOT NULL AND...