The problem is cross-path expressions, which are not yet handled in that manner
for simple expressions that only contain a single piece of the path (node, rel)
and things that have been evaluated before (parameters, literals, previous
computations) WILL be used to shortcut the path evaluation.
but if you do: n1--n2--n3
and then WHERE n2.foo > n1.bar it will be only applied AFTER the path
if you do: WHERE n1.foo > 10 it will be applied DURING the path traversal
HTH
Michael
Am 21.01.2014 um 18:08 schrieb Javad Karabi <karabija...@gmail.com>:
> You will notice:
> "WHERE (Property(NodeIdentifier(),cached_available(71)) == Literal(1)" in the
> TraversalMatcher() portion, the very first function of the profile..
>
> I believe that this is what is meant when the documentation says that the
> WHERE clause is not done after, (therefore during) the matching process.
>
> However, you will also notice that immediately following that function, is
> Filter(), which is then filtering based on the ">" and "<" predicates of the
> query.
>
> obviously, the best case scenario would be if the ">" and "<" tests occurred
> inside TraversalMatcher(), i think
>
> On Tuesday, January 21, 2014 11:06:06 AM UTC-6, Javad Karabi wrote:
> Mark, I have emailed you the query and profile for both cases.
>
> On Tuesday, January 21, 2014 10:55:03 AM UTC-6, Javad Karabi wrote:
> Mark, I would be happy to. Give me a moment and I will post them.
>
> Michael,
> Kernel version
>
> neo4j-browser, version: 2.0.0
>
>
> On Tuesday, January 21, 2014 10:49:37 AM UTC-6, Michael Hunger wrote:
> Java, what version are you using?
>
> 2.0 final?
>
> Michael
>
> Am 21.01.2014 um 17:29 schrieb Javad Karabi <karab...@gmail.com>:
>
>> from what I can tell, if there where clause is ">" or "<" (as it is in the
>> actual query which i am using, not in this example query...) then the WHERE
>> predicate _is in fact_ a filter, applied _after_ the match. It looks to me
>> that "TraversalMatcher()" does not apply predicates which involve > or <,
>> but instead delegates this to "Filter()" after the fact, which does not
>> correlate with what is stated on the documentation.
>>
>> On Tuesday, January 21, 2014 10:25:41 AM UTC-6, Javad Karabi wrote:
>> (c:Customer)-[:ordered]->(p:Product)-[:category]->(:Category)
>>
>> Now, say that there are 2:
>> c-[:ordered]->(:Product { name: "pants", quantity: 10})
>> c-[:ordered]->(:Product { name: "shirt", quantity: 5})
>>
>> Now, say that if I only want to cross the category relationship if the
>> p.quantity > 6
>>
>> In the most basic way, I would do:
>>
>> (c:Customer)-[:ordered]->(p:Product)-[:category]->(cat:Category)
>> WHERE p.quantity > 6
>>
>> However, I figured that maybe neo4j would (non-optimally) traverse the
>> entire path _then_ filter where on top of the path.
>>
>> So what I did was:
>>
>> MATCH (c:Customer)-[:ordered]->(p:Product)
>> WHERE p.quantity > 6
>> WITH p
>> MATCH p-[:category]->(cat:Category)
>>
>> This, I figured, would then allow neo4j to cross out to all the product
>> nodes, as I would need them anyway in order to filter out the ones which
>> have a quantity of less than 6.
>>
>>
>> Now... finally to my question.
>> The following URL:
>> http://docs.neo4j.org/chunked/stable/query-match.html
>> states that:
>> WHERE defines the MATCH patterns in more detail. The predicates are part of
>> the pattern description, not a filter applied after the matching is done.
>>
>> So, my question is, if the predicates (specifically p.quantity > 6) are part
>> of the pattern description, and _not_ applied _after_ matching (therefore
>> applied before or during), then cutting the query with the WITHs would be a
>> moot point
>>
>> So, I would think that
>>
>> (c:Customer)-[:ordered]->(p:Product)-[:category]->(cat:Category)
>> WHERE p.quantity > 6
>>
>> would be sufficient, , as neo4j _would not_ actually traverse to cat, since
>> it would apply the filter during the match process.
>>
>> However, in practice, I notice that using WITH is actually faster. Is there
>> any possible reason for this?
>> It may be necessary for me to show my query exactly, I also have the profile
>> data for the query, which I am currently analyzing
>>
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