Please support val function on facets

Moved from GitHub dgraph/4520

Posted by ChStark:

What you wanted to do

If we have an upsert block like:

upsert{
  query{
   	product( func: uid( 0x12a4f4e ) ){
      wholesale_price as product.wholesale_price    
      wholesale_tax as product.wholesale_tax
      regular_price as product.regular_price
      regular_tax as product.regular_tax
  	}
    user( func: uid( 0x12a4f31 ) ){
      is_wholesaler as user.is_wholesaler
    }
  }
  mutation @if( eq( val(is_wholesaler) , true ) ){
    set{
      <0x12a4f31> <user.orders> <0x12a4f55> .
      <0x12a4f55> <order.products> <0x12a4f4e> (quantity=5, price=val(wholesale_price), tax=val(wholesale_tax) ) .
    }
  }
  mutation @if( not( eq( val(is_wholesaler) , true ) ) ){
    set{
      <0x12a4f31> <user.orders> <0x12a4f55> .
      <0x12a4f55> <order.products> <0x12a4f4e> (quantity=5, price=val(regular_price), tax=val(regular_tax) ) .
    }
  }
} 

It wont work since the val function is not supported on facets

What you actually did

The work around is to do a 2 part job, one to query the data and one to do the mutation, but since dgraph wants to reduce the network trips, I thinks this should be supported

Why that wasn’t great, with examples

It wasn’t great that I had to handle more logic on the app just because the QL doesn’t support the parsing of a function

MichelDiz commented :

Although issue #1996’s proposal is different, it has a similar goal.

ChStark commented :

Maybe we can achieve the goal of both issues changing the syntaxis (have inmmutability and consistency on the edge attributes and the ability to use val)

upsert{
  query{
   	product( func: uid( 0x12a4f4e ) ){
      wholesale_price as product.wholesale_price    
      wholesale_tax as product.wholesale_tax
      regular_price as product.regular_price
      regular_tax as product.regular_tax
  	}
    user( func: uid( 0x12a4f31 ) ){
      is_wholesaler as user.is_wholesaler
    }
  }
  mutation @if( eq( val(is_wholesaler) , true ) ){
    set{
      <0x12a4f31> <user.orders> <0x12a4f55> .
      <0x12a4f55> <order.products> <0x12a4f4e> (quantity=5, price=val(wholesale_price), tax=val(wholesale_tax) ) .
    }
  }
  mutation @if( not( eq( val(is_wholesaler) , true ) ) ){
    set{
      <0x12a4f31> <user.orders> <0x12a4f55> .
      <0x12a4f55> <order.products> <0x12a4f4e> 5#quantity .
      <0x12a4f55> <order.products> <0x12a4f4e> val(regular_price)#price .
      <0x12a4f55> <order.products> <0x12a4f4e> val(regular_tax)#tax .
    }
  }
} 

Doing something like this we can have something that currently works ( val on values of nquad ) and indicate to the parser what specific facet we want to mutate to change only that one and not to mutate the other ones