modifying an array property in cypher

[Mat Tyndall]

So I'm trying to check to see if a value exists in an array on a node and then if it doesn't add it. 

Example: check if 'c' is present in (node {array:['a','b']}) and if not add it (node {array:['a','b','c']}).

I get the feeling with the various functions that I can iterate through the array and use regular expressions to test each value but how do I then push a new value into the array?

I'm pretty sure I could split it into 2 queries but one would be better.

I'm going to experiment in the console but if anybody has already solved this problem I'd love to see.

[Mat Tyndall]

So turns out adding to an array is easy, "SET node.array = node.array + value", however I can't figure out how to conditionally create the array property if it doesn't exist without splitting this into 2 queries.

[Michael Hunger]

Usually you should be able to do:

start node = ...

where {value} in node.array

set node.array = node.array + {value}

Please try this

Michael

[Mat Tyndall]

that works, but if the array property hasn't been created yet it throws an error.

[Russell Duhon]

Hi,

First time posting on the list, but I've been doing some similar stuff.

You can deal with the not-yet-created problem with coalesce, eg

start node = ...
set node.array = coalesce(node.array?, []) + value

(Just tried it out on a reasonably recent milestone).

I hope that helps,
Russell

[Michael Hunger]

Thanks Russell, that's correct, I think we should add an example for this whole use-case to the manual.

Michael

[Mat Tyndall]

Awesome, thanks Russel and Michael! I knew I was missing a permutation.

And to round things out, to remove a value from an array I use the following query:

SET node.array = filter(x in node.array : not(x=value))

And yeah, adding more of these sorts of queries to the examples would be great.

-Mat

On Sunday, July 1, 2012 12:13:19 AM UTC-7, Michael Hunger wrote:

Thanks Russell, that's correct, I think we should add an example for this whole use-case to the manual.

Michael

Am 01.07.2012 um 01:46 schrieb Russell Duhon:

Hi,

First time posting on the list, but I've been doing some similar stuff.

You can deal with the not-yet-created problem with coalesce, eg

start node = ...
set node.array = coalesce(node.array?, []) + value

(Just tried it out on a reasonably recent milestone).

I hope that helps,
Russell

[Bharathi Raja]

Hey  i used the below query it works fine for me

match (me:Person{name:"Raja"}) set me.degree=me.degree+["UG","PG"] return me


Enjoy