Databases Reference
In-Depth Information
and therefore have no incoming
DELIVERY_ROUTE
relationships, we can be confident
that the
db1
node at the end of this variable-length path represents a delivery base
and not some other parcel network element.
•
WHERE
applies additional constraints to the path
upLeg
, ensuring that we only match
DELIVERY_ROUTE
relationships whose
start_date
and
end_date
properties en‐
compass the supplied delivery period.
The second subquery calculates the second leg of the route, which comprises the path
from the end location to another delivery center elsewhere in the network. This query
is very similar to the first:
WITH
e, upLeg, db1
MATCH
downLeg = (db2)-[:DELIVERY_ROUTE*1..2]->(e)
WHERE
all
(r
in
relationships
(downLeg)
WHERE
r.start_date <=
{intervalStart}
AND
r.end_date >=
{intervalEnd}
)
The
WITH
clause here chains the first subquery to the second, piping the end location
and the first leg's path and delivery base to the second subquery. The second subquery
uses only the end location,
e
, in its
MATCH
clause; the rest is provided so that it can be
piped to subsequent queries.
The third subquery identifies
all
candidate paths for the third leg of the route, as follows:
WITH
db1, db2, upLeg, downLeg
MATCH
topRoute = (db1)<-[:CONNECTED_TO]-()-[:CONNECTED_TO*1..3]-(db2)
WHERE
all
(r
in
relationships
(topRoute)
WHERE
r.start_date <=
{intervalStart}
AND
r.end_date >=
{intervalEnd}
)
This subquery is broken down as follows:
•
WITH
chains this subquery to the previous one, piping the delivery bases and paths
identified in legs one and two to the current query.
•
MATCH
identifies
all
paths between the first and second leg delivery bases, to a max‐
imum depth of four, and binds them to the
topRoute
identifier.
•
WHERE
constrains the
topRoute
paths to those whose
start_date
and
end_date
properties encompass the supplied delivery period.
The fourth and final subquery selects the shortest path for leg three, and then calculates
the overall route:
WITH
upLeg, downLeg, topRoute,
reduce
(weight=0, r
in
relationships
(topRoute) : weight+r.cost)
AS
score
ORDER BY
score
ASC
LIMIT
1
RETURN
(
nodes
(upLeg) +
tail
(
nodes
(topRoute)) +
tail
(
nodes
(downLeg)))
AS
n
