· neo4j cypher

Neo4j: Procedure call inside a query does not support passing arguments implicitly (pass explicitly after procedure name instead)

A couple of days I was trying to write a Cypher query to filter the labels in my database.

I started with the following procedure call to get the list of all the labels:


CALL db.labels

╒══════════╕
│label     │
╞══════════╡
│Airport   │
├──────────┤
│Flight    │
├──────────┤
│Airline   │
├──────────┤
│Movie     │
├──────────┤
│AirportDay│
├──────────┤
│Person    │
├──────────┤
│Engineer  │
└──────────┘

I was only interested in labels that contained the letter 'a' so I tweaked the query to filter the output of the procedure:


CALL db.labels
YIELD label 
WITH label WHERE tolower(label) contains "a"
RETURN label

Unfortunately that didn't work as I expected:


Procedure call inside a query does not support passing arguments implicitly (pass explicitly after procedure name instead) (line 1, column 9 (offset: 8))
"CALL db.labels"
         ^

The mistake I made was calling the procedure implicitly without using parentheses. If you want to do any post processing on the output of a procedure you need to call it explicitly otherwise Cypher gets very confused.

If we add back the parentheses it's much happier:


CALL db.labels()
YIELD label 
WITH label WHERE tolower(label) contains "a"
RETURN label

╒══════════╕
│label     │
╞══════════╡
│Airport   │
├──────────┤
│Airline   │
├──────────┤
│AirportDay│
└──────────┘

It stumped me for a while until I figured out what the error message meant! I think I'll just use explicit parentheses all the time from now on to save me running into this one again.

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