Neo4j: why the performance of allShortestPaths function is so slow? - performance

Question

I am using Neo4j 'neo4j-community-2.3.0-RC1' version.
In my database there are just 1054 nodes.
when i do path query with 'allShotestPaths' function, why it is so slow.
it take about more than 1 second,the following is unit test result :
√ search optimalPath Path (192ms)
√ search optimal Path by Lat Lng (1131ms)
should i optimize the query? the following are querys for 'optimalPath' and 'optimal Path by Lat Lng'
optimalPath query:
MATCH path=allShortestPaths((start:潍坊_STATION )-[rels*..50]->(end:潍坊_STATION {name:"火车站"}))
RETURN NODES(path) AS stations,relationships(path) AS path,length(path) AS stop_count,
length(FILTER(index IN RANGE(1, length(rels)-1) WHERE (rels[index]).bus <> (rels[index - 1]).bus)) AS transfer_count,
length(FILTER( rel IN rels WHERE type(rel)="WALK" )) AS walk_count
order by transfer_count,walk_count,stop_count
optimal Path by Lat Lng query:
MATCH path=allShortestPaths((start:潍坊_STATION {name:"公交总公司"})-[rels*..50]->(end:潍坊_STATION {name:"火车站"}))
WHERE
round(
6378.137 *1000*2*
asin(sqrt(
sin((radians(start.lat)-radians(36.714))/2)^2+cos(radians(start.lat))*cos(radians(36.714))*
sin((radians(start.lng)-radians(119.1268))/2)^2
))
)/1000 < 0.5 // this formula is used to calculate the distance between two GEO coordinate (latitude\longitude)
RETURN NODES(path) AS stations,relationships(path) AS path,length(path) AS stop_count,
length(FILTER(index IN RANGE(1, length(rels)-1) WHERE (rels[index]).bus <> (rels[index - 1]).bus)) AS transfer_count,
length(FILTER( rel IN rels WHERE type(rel)="WALK" )) AS walk_count
order by transfer_count,walk_count,stop_count
you can download the database here:https://www.dropbox.com/s/zamkyh2aaw3voe6/data.rar?dl=0
i will be very grateful ,if anybody can help me. thanks

Answer 1

In general, without knowing more, I would pull the predicates and expressions that can be computed before the paths are all expanded, before the match.
And as your geo-filter is independent of anything else except your parameters and the start-node you can do:
MATCH (start:潍坊_STATION {name:"公交总公司"})
WHERE
// this formula is used to calculate the distance between two GEO coordinate (latitude\longitude)
round(6378.137 *1000*2*
asin(sqrt(sin((radians(start.lat)-radians({lat}))/2)^2
+cos(radians(start.lat))*cos(radians({lat}))*
sin((radians(start.lng)-radians({lng}))/2)^2)))/1000
< 0.5
MATCH (end:潍坊_STATION {name:"火车站"})
MATCH path=allShortestPaths((start)-[rels*..50]->(end))
RETURN NODES(path) AS stations,
relationships(path) AS path,
length(path) AS stop_count,
length(FILTER(index IN RANGE(1, length(rels)-1)
WHERE (rels[index]).bus <> (rels[index - 1]).bus)) AS transfer_count,
length(FILTER( rel IN rels WHERE type(rel)="WALK" )) AS walk_count
ORDER BY transfer_count,walk_count,stop_count;
see this test (but the other query is equally fast):
neo4j-sh (?)$ MATCH (start:潍坊_STATION {name:"公交总公司"})
>
> WHERE
> // this formula is used to calculate the distance between two GEO coordinate (latitude\longitude)
> round(6378.137 *1000*2*
> asin(sqrt(sin((radians(start.lat)-radians({lat}))/2)^2
> +cos(radians(start.lat))*cos(radians({lat}))*
> sin((radians(start.lng)-radians({lng}))/2)^2)))/1000
> < 0.5
>
> MATCH (end:潍坊_STATION {name:"火车站"})
> MATCH path=allShortestPaths((start)-[rels*..50]->(end))
> WITH NODES(path) AS stations,
> relationships(path) AS path,
> length(path) AS stop_count,
> length(FILTER(index IN RANGE(1, length(rels)-1)
> WHERE (rels[index]).bus <> (rels[index - 1]).bus)) AS transfer_count,
> length(FILTER( rel IN rels WHERE type(rel)="WALK" )) AS walk_count
>
> ORDER BY transfer_count,walk_count,stop_count
> RETURN count(*);
+----------+
| count(*) |
+----------+
| 320 |
+----------+
1 row
10 ms