Support lists in query variables (DQL Variable)

[F21]

Experience Report

I often have queries where I want to match a list of things (similar to an IN query in SQL). For example:

{
  someQuery(func: eq(somePredicate, val1, val2){
    someField
  }
}

Often, these values come from user input and I want to pass these values to the query using query variables.

Effectively, this would allow a query like so:

query($vals: []string){
  someQuery(func: eq(somePredicate, $vals){
    someField
  }
}

What you wanted to do

I wanted to pass a list of values as a query variable into a query.

What you actually did

I had to create the query programmatically using string concatenation.

Why that wasn't great, with examples

Having to use string concatenation introduced a lot of noise into the code and the query was very unreadable.

Any external references to support your case

None.

[MichelDiz]

Note: This seems duplicated of #2272
PS. Just a note.

[MichelDiz]

Hey @F21 , I gonna close this issue due duplicate. To keep just one issue tracking this, the 2272.

Anyway thanks for the care of having opened an issue for this.

Cheers.

[MichelDiz]

Well I'm reopening this due some changes and more info related to GraphQL standard.

The issue #2272 was solved, but it was specific for block arrays, with an example of payload
with array. But it did not go deep into adding an array to the var type itself.

Now I see that this issue appears to be more specific for this case.

As Dgraph intends to get closer to GraphQL's standard. I believe this is a good feature for this.
In GraphQL you can add arrays to the variables used in a Query. e.g:

{
  query: `
    query events ($containsId: [Int]) { 
     # the parse results  events(containsId: [1,2,3]) {
      events(containsId: $containsId) {
        id
        name
      }
    }
  `,
  variables: {
    containsId: [1,2,3]
  }
}

UPDATE:

Also there's an issue with Documentation that says about the possibility to use arrays for UID.

Check https://docs.dgraph.io/query-language/#graphql-variables

Testing in https://play.dgraph.io/ I can't put a list of UIDs to work as docs says.

Note If you want to input a list of uids as a GraphQL variable value, you can have the variable as string type and have the value surrounded by square brackets like ["13", "14"].

I've tested several combinations and none was successful as docs mention.

query q($name1:string = ["0x1878bd", "0x237702"]) {
   me(func: uid( $name1 )) {
    uid
    name@en
    director.film @filter(lt(initial_release_date, "1980-01-01"))  {
      initial_release_date
      name@en
    }
  }
}

"0x1878bd, 0x237702" are "Ridley Scott" and "Steven Spielberg" uids.

[srfrog]

This is similar to #2272 but it's in fact a different feature. The variable array (Gql) is not the same as the argument list. We would need to add support for arrays and convert them into argument list for this to work.

The uid list is not the same as the array in the variable. This is how it works:

{
   //            .... argument list ....
   me(func: uid( "0x1878bd", "0x237702" )) {
    uid
    name@en
    director.film @filter(lt(initial_release_date, "1980-01-01"))  {
      initial_release_date
      name@en
    }
  }
}

[MichelDiz]

The uid list is not the same as the array in the variable.

Yeah, I know. But the point is that the Docs indicates that it is possible to use array for UIDs with Graphql Vars. I have not found any way to make it work according to the "Note" from docs.

[d4l3k]

Any update on this? I'd really like to be able to do

query docs($urls: [string]) {
  docs(func: eq(url, $urls)) {
    title
    desc
  }
}

but it sounds like it's not currently supported. Coming from the SQL world this seems like a very basic operation that should be supported.