Update item in document array

[noahehall]

hello arangotans

playing on the solution to this issue

problem: update an item, in an array, on a document error: ArangoError: AQL: collection or array expected as operand to FOR loop; you provided a value of type 'null'

sample document:

 {
   key: jordan_greenhall,
   music: [
     { id: 2pac },
     {id: nipsey},
     {id; mozzy}
   ]
}

query throwing error

   aql`
          LET doc = DOCUMENT(${collectionName}/${thisDocKey})
          let itemId = ${itemId}
          let obj = ${obj}
          let prop = ${prop}
          let updated = (
            FOR item in doc[prop]
            FILTER item.id == itemId
            return MERGE(item, obj)
          )
          UPDATE doc WITH { [prop]: updated} in ${db.collection(collectionName)}
          RETURN doc

        `

obviously its an error with arango, and not my query ;)

[noahehall]

this indeed works in directly in the arango web interface query thing

LET doc = DOCUMENT("Paths/account-collectors")
let itemId = 'base'
let obj = { wtf: 'yo' }
let prop = 'strategies'

let updated = (
FOR item in doc[prop]
FILTER item.id == itemId
return MERGE(item, obj)
)
UPDATE doc WITH { [prop]: updated} in 'Paths'
RETURN doc

but fails when I use the node arango thing

[noahehall]

if anyone else arrives here thinking wtf the solution was definitely thinking about the returned error.

in node you have to declare the variables within the aql template

working query:

aql`
          let colName = ${collectionName} // <---
          let key = ${thisDocKey} // <---
          LET doc = DOCUMENT(colName,key) // <---
          let itemId = ${itemId}
          let obj = ${obj}
          let prop = ${prop}

          let updated = (
            FOR item in doc[prop]
            FILTER item.id == itemId
            return MERGE(item, obj)
          )
          UPDATE doc WITH { [prop]: updated} in ${db.collection(collectionName)}
          RETURN doc

        `

[noahehall]

is there a better way to do what im doing here? e.g.

• since I know the id of the item in the array, can I just retrieve it without the for loop?
• how do I test for falsy (if (!doc || doc[prop]) and escape ealry?

also intriguingly this works elseware in my file

RETURN UNSET(DOCUMENT("${collectionName}/${thisDocKey}"), "_key", "_id", "_rev")

Why do I have to use the intermediate variables when doing the loop?

• nh

[noahehall]

@jsteemann ^^

[noahehall]

ps, always return NEW mf

[noahehall]

ps read this https://www.arangodb.com/docs/3.6/aql/examples-data-modification-queries.html

in the loop you have to check each item MERGE only the matching item, else you'll rewrite the entire prop