apoc.refactor.mergeNodes while using apoc.periodic.iterate seems not working

[SimG92]

Hello,
in my database I have multiple nodes that have the same properties, so I want to merge all of these nodes into one. Those nodes are connected by the relationship "similar", so I use gds weakly connected component to find these communities, then I'm using the following code to merge those nodes in the same community while using the apoc.periodic.iterate

CALL apoc.periodic.iterate('
MATCH (n:Officer)
WITH n.community AS com, collect(n) AS nodicom
RETURN nodicom
','
CALL apoc.refactor.mergeNodes(nodicom,{
properties:"discard", mergeRels:true, preserveExistingSelfRels:false}) YIELD node
',{batchSize: 200, parallel: true})
YIELD batches, total
RETURN batches, total

I'm expecting that all nodes grouped by community will be merged but it does not working.
Using the following code I have a lot of communities with more than 1 node:

match (n) with n.community as com, count(n) as contacom return com, contacom order by contacom desc

if I use:

MATCH (n:Officer) where n.community=239389
WITH n.community AS com, collect(n) AS nodicom
CALL apoc.refactor.mergeNodes(nodicom,{
properties:"discard", mergeRels:true, preserveExistingSelfRels:false})
yield node
return count(*)

it works. 239389 is an example of id community

Neo Desktop Version: 1.5.8
Database Version 5.5.0
APOC Version 5.5.0
on Windows 11 Home

[nadja-muller]

Thank you for reporting this. We will have a look and come back to you.

[SimG92]

Thank you for reporting this. We will have a look and come back to you.

Thanks!

[cybersam]

Minor typo: The title of this Issue should say mergeNodes instead of merge.

[SimG92]

Minor typo: The title of this Issue should say mergeNodes instead of merge.

Correct! Sorry :)

[gem-neo4j]

Hi! Sorry for the slow response, I took a look, and the problem seems to be that apoc.periodic.iterate swallows errors, so your query is not working.

Your query:

CALL apoc.periodic.iterate('
MATCH (n:Officer)
WITH n.community AS com, collect(n) AS nodicom
RETURN nodicom
','
CALL apoc.refactor.mergeNodes(nodicom,{
properties:"discard", mergeRels:true, preserveExistingSelfRels:false}) YIELD node <--- ERROR HERE
',{batchSize: 200, parallel: true})
YIELD batches, total
RETURN batches, total

In the second query, you are trying to end a query with a YIELD, which is invalid Cypher, you need to add "RETURN node" to make it work. This error will be logged in debug.query.

We recommend using Cypher over APOC to get the benefit of memory tracking and statistics, as well as proper error handling. I recommend you take a look at Cypher's CALL IN TRANSACTIONS, which offers you everything you are trying to do here without APOC :)