Allow deletion of specific language.

[martinmr]

This change introduces the syntax "<s> <p@lang> * ." to allow users to
delete a specific language tagged value without having to specify the
current value.

Closes #3237

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This change is 

[srfrog]

Reviewed 4 of 4 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved

[srfrog]

Reviewable status: complete! all files reviewed, all discussions resolved

[MichelDiz]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @manishrjain and @martinmr)

a discussion (no related file):
Can we extend this to JSON? e.g:

  {
      "delete": [
        {
          "uid": "0x12345",
         "name@es": null
        }
      ]
    }

equivalent to:

<0x12345> <name@es> * .

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[martinmr]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @manishrjain and @MichelDiz)

a discussion (no related file):

Previously, MichelDiz (Michel Conrado) wrote…

Can we extend this to JSON? e.g:

  {
      "delete": [
        {
          "uid": "0x12345",
         "name@es": null
        }
      ]
    }

equivalent to:

<0x12345> <name@es> * .

it should already work for JSON if the two representations are identical (produce the same DirectedEdge object when parsed). I'll add a test to the json parser to verify this is the case.

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[martinmr]

Reviewable status: 4 of 5 files reviewed, 1 unresolved discussion (waiting on @manishrjain and @MichelDiz)

a discussion (no related file):

Previously, martinmr (Martin Martinez Rivera) wrote…

it should already work for JSON if the two representations are identical (produce the same DirectedEdge object when parsed). I'll add a test to the json parser to verify this is the case.

Added tests but this is the right syntax.

{
      "delete": [
        {
          "uid": "0x12345",
         "name@es": ""
        }
      ]
 }

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[martinmr]

Reviewable status: 4 of 5 files reviewed, 1 unresolved discussion (waiting on @manishrjain and @MichelDiz)

a discussion (no related file):

Previously, martinmr (Martin Martinez Rivera) wrote…

Added tests but this is the right syntax.

{
      "delete": [
        {
          "uid": "0x12345",
         "name@es": ""
        }
      ]
 }

Done.

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[MichelDiz]

Reviewable status: 4 of 5 files reviewed, 1 unresolved discussion (waiting on @manishrjain and @martinmr)

a discussion (no related file):

Previously, martinmr (Martin Martinez Rivera) wrote…

Done.

I see, the empty string works indeed. But Docs says that "rating": null is a S P * operation syntax. https://docs.dgraph.io/mutations/#deleting-edges - If empty strings are to be considered, for me it's okay.

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[MichelDiz]

Reviewable status: 4 of 5 files reviewed, all discussions resolved (waiting on @manishrjain)

[martinmr]

Reviewable status: 4 of 5 files reviewed, all discussions resolved (waiting on @manishrjain)

a discussion (no related file):

Previously, MichelDiz (Michel Conrado) wrote…

I see, the empty string works indeed. But Docs says that "rating": null is a S P * operation syntax. https://docs.dgraph.io/mutations/#deleting-edges - If empty strings are to be considered, for me it's okay.

This seems like a bug. The language tag is not being parsed properly. I'll revert these test changes and open a new PR to fix the bug. But otherwise, JSON support should work out of the box.

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[manishrjain]

And how would this deletion work in JSON?

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @manishrjain)

[martinmr]

I had to submit #3243 to make this work but it should work in the following way:

{
 "uid":"0xa",
"name@en":null
}

Reviewable status: complete! all files reviewed, all discussions resolved