Javad,
Can you paste the PROFILE output for the two queries on here. In theory the
two queries should do the same thing...in practice I imagine that's not the
case!
Mark
On 21 January 2014 16:29, Javad Karabi <karabija...@gmail.com> wrote:
> 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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