'Returning a map object in cypher

I need to create edges between a set of nodes but it is not guaranteed that the edge is not exists already, I need to know which edges has been created so I can increment the edges counter for the two connected nodes.

I want to know the edges count for every node without querying the graph each time.

Example:

MERGE (u:user {id:999049043279872})
MERGE (g1:group {id:346709075951616})
MERGE (g2:group {id:346709075951617})
MERGE (g1)-[m1:member]->(u)
MERGE (g2)-[m2:member]->(u)

Sometimes the user is already a member of the group so I don't want to increment the counter in this case.

I tried to use the result statistics but it returns the created relationships number only, I thought also about using a map and then fill the content using ON CREATE SET after MERGE:

WITH {g1:0, g2:0} as res
MERGE (u:user {id:999049043279872})
MERGE (g1:group {id:346709075951616})
MERGE (g2:group {id:346709075951617})
MERGE (g1)-[m1:member]->(u)
ON CREATE SET res.g1 = 1
MERGE (g2)-[m2:member]->(u)
ON CREATE SET res.g2 = 1
RETURN res

But it does not works; the server crashes immediately after executing the query.

Exception:

------ FAST MEMORY TEST ------
17235:M 28 Feb 2022 16:56:50.016 # main thread terminated
17235:M 28 Feb 2022 16:56:50.017 # Bio thread for job type #0 terminated
17235:M 28 Feb 2022 16:56:50.017 # Bio thread for job type #1 terminated
17235:M 28 Feb 2022 16:56:50.018 # Bio thread for job type #2 terminated

Fast memory test PASSED, however your memory can still be broken.
Please run a memory test for several hours if possible.

------ DUMPING CODE AROUND EIP ------
Symbol: (null) (base: (nil))
Module: /lib/x86_64-linux-gnu/libc.so.6 (base 0x7fbfe3dcc000)
$ xxd -r -p /tmp/dump.hex /tmp/dump.bin
$ objdump --adjust-vma=(nil) -D -b binary -m i386:x86-64 /tmp/dump.bin

=== REDIS BUG REPORT END. Make sure to include from START to END. ===

Please report the crash by opening an issue on github:

http://github.com/redis/redis/issues

Suspect RAM error? Use redis-server --test-memory to verify it.

Segmentation fault

Any ideas?

Thanks in advance

cypherredisgraph


Solution 1:[1]

Neo4j stores already a counter inside each node to count the number of relationships and to provide a fast count access. When you want to get the number of members in a group, you can simply do:

MATCH (g:group)
return size((g)<-[:member]-())

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Sbunzini

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