Can't match-where-limit in Cypher?

user_1877527 0
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It's a simple query, but for some reason it's not working

SELECT (n:myBaseLabel) WHERE NOT n:myPossibleSubLabel LIMIT 20

This is the most simple case, where I really don't care what gets returned. The objective is to run

SELECT (n:myBaseLabel) WHERE NOT n:myPossibleSubLabel AND NOT n:myExclusionLabel SET n:myExclusionLabel LIMIT 25000

in a loop to iteratively apply the label myExclusionLabel to instances of myBaseLabel that don't have myPossibleSubLabel. Both the iterative loop and the existence of this exclusion label are for performance reasons in querying the graph, since it has ~50M nodes. Since I'm looping and excluding, I don't care about which get tagged in a given loop, I just want to reduce the memory load while breaking the execution into chunks so I don't entirely lock up the database for a day updating this.

However, in the simple test case I keep getting an error at the I of LIMIT, saying:

Invalid input 'I': expected 'o/O' (line 1, column 58 (offset: 57))

which makes no sense to me.

cypher neo4j
1 Answers

Figured out how. Very unintuitively, you need to limit before the operation after a WITH.

MATCH (n:myBaseLabel)
WHERE NOT n:myPossibleSubLabel AND NOT n:myExclusionLabel 
WITH n
LIMIT {updateChunk}
SET n:myExclusionLabel 
RETURN count(n)
user_18775270
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