The answer on slide 8 of the browser guide indicates that the correct way to introduce pattern comprehension to this query:
PROFILE
MATCH (a:Actor)-[:ACTED_IN]->(m:Movie)
WHERE $relYear1 <= m.releaseYear <= $relYear2 AND a.born > $yearBorn
RETURN a.name as actor, a.born as born,
collect(DISTINCT m.title) AS titles ORDER BY actor
is like so:
PROFILE
MATCH (a:Actor)
WHERE a.born > $yearBorn
RETURN a.name AS actor, a.born AS born,
[(a)-->(x) WHERE $relYear1 <= x.releaseYear <= $relYear2 | x.title] AS titles ORDER BY actor
Which generates 95036 hits in 49 ms. My questions are:
-
why is there seemingly no performance penalty from using [(a)-->(x).. rather than [(a)-[:ACTED_IN]->(m:Movie)..? Does pattern comprehension really not care about having no relationship type or node labels included in this way?
-
if you did swap to the the more explicit syntax of [(a)-[:ACTED_IN]->(m:Movie).., then you must include WITH DISTINCT a before the return statement, otherwise there are duplicate rows for each actor - why is this?
-
if you use the documented syntax of [(a)-->(x).. it's possible to to get a slightly faster execution time by adding a WITH DISTINCT a clause first (a few ms), but strangely this increases dbhits to 98273. Can anyone explain why?
