neo4j - cypher union group by sum -

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i boost edges user depending of rules base on graph traversal. in mysql :

select id, sum(weight) total (      select id, 10 weight      user      inner join userrel1 on user.id = userrel1.userid      userrel1.attr1 in (1, 2)   union      select id, 5 weight      user      inner join userrel2 on user.id = userrel2.userid      inner join userrel3 on user.id = userrel3.userid      userrel2.attr2 = 'a' , userrel3.attr2 = 'z'   union      ... ) group id  order total desc

also, have writed query in gremlin 3 compare performance cypher. read in post group on union not possible yet, mean cypher less powerful gremlin ? have set weight properties on edges achieve ?

thanks

while true post-union processing still open feature request, not need use union perform use case.

this query should equivalent of sql (ignoring incomplete part):

with [] res  optional match (user1:user), (userrel1:userrel1)  user1.id = userrel1.userid , userrel1.attr1 in [1, 2]  res, (case when userrel1 not null collect({id: user1.id, weight: 10}) else [] end) data  res + data res  optional match (user2:user), (userrel2:userrel2) user2.id = userrel2.userid , userrel2.attr2 = 'a' optional match (userrel3:userrel3) user2.id = userrel3.userid , userrel3.attr2 = 'z'  res, (case when userrel3 not null collect({id: user2.id, weight: 5}) else [] end) data  res + data res   unwind res result return result.id, sum(result.weight) weight;

i visually broke query separate blocks of cypher, make easier read.

the query keeps extending (and replacing) res collection appropriate id/weight pairs, , aggregates @ end.

the block 2 optional match clauses have been written using single optional match, thought more performant same work piecemeal, , allow failure of 1 optional match potentially inform cypher not bother other one. block's second where clause relies on user2 node found first optional match. user2 have value null if first optional match failed, , such null value cause second where clause fail (which in turn make userrel3 null).


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