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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