apoc.agg.first

Details
Syntax	`apoc.agg.first(value)`
Description	Returns the first value from the given collection.
Arguments	Name	Type	Description
	`value`	`ANY`	A value to be aggregated.
Returns	`ANY`

Usage examples

The examples in this section are based on the following sample graph:

CREATE (Keanu:Person {name:'Keanu Reeves', born:1964})
CREATE (TomH:Person {name:'Tom Hanks', born:1956})

CREATE (TheMatrix:Movie {title:'The Matrix', released:1999, tagline:'Welcome to the Real World'})
CREATE (TheMatrixReloaded:Movie {title:'The Matrix Reloaded', released:2003, tagline:'Free your mind'})
CREATE (TheMatrixRevolutions:Movie {title:'The Matrix Revolutions', released:2003, tagline:'Everything that has a beginning has an end'})
CREATE (YouveGotMail:Movie {title:"You've Got Mail", released:1998, tagline:'At odds in life... in love on-line.'})
CREATE (SleeplessInSeattle:Movie {title:'Sleepless in Seattle', released:1993, tagline:'What if someone you never met, someone you never saw, someone you never knew was the only someone for you?'})

CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrix)
CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrixReloaded)
CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrixRevolutions)

CREATE (TomH)-[:ACTED_IN {roles:['Joe Fox']}]->(YouveGotMail)
CREATE (TomH)-[:ACTED_IN {roles:['Sam Baldwin']}]->(SleeplessInSeattle);

This function provides a more efficient way of getting the first value in a collection. For example, to find the earliest movie that each person has acted in, we could write the following query:

Cypher

MATCH (p:Person)-[:ACTED_IN]->(movie)
WITH p, movie
ORDER BY p, movie.released
RETURN p.name AS person, collect(movie)[0] AS earliestMovie;

This query collects all of the movies into memory, before returning just the first one. We can avoid this build up of in memory state by using the apoc.agg.first aggregation function, as shown below:

apoc.agg.first

MATCH (p:Person)-[:ACTED_IN]->(movie)
WITH p, movie
ORDER BY p, movie.released
RETURN p.name AS person, apoc.agg.first(movie) AS earliestMovie;

Results
person	earliestMovie
"Tom Hanks"	(:Movie {tagline: "What if someone you never met, someone you never saw, someone you never knew was the only someone for you?", title: "Sleepless in Seattle", released: 1993})
"Keanu Reeves"	(:Movie {tagline: "Evil has its winning ways", title: "The Devil’s Advocate", released: 1997})