Queries inside document insert/replaces

[matko]

Right now, it's still a bit tricky to establish links to existing documents from newly inserted documents, or replacement documents. You have to know the id of the document you want to link to in advance, which requires at least one more query to happen in a separate request. This is definitely not ideal.

It would be nice if we could use document queries to find documents we could link to. For example,

{ "@type": "Person",
  "name": "Belle",
  "friends": {"@query-all": {"@type": "Person",
                             "name": {"@one-of": ["Alice", "Claire"]}}}
}

Or

{ "@type": "Person",
  "name": "Belle",
  "spouse": {"@query-one": {"@type": "Person",
                            "name": "David"}}
}

so @query-all would return a list, which can then be put into a field that expects a set, a list, or an array, and @query-one would be used to just query for a single item (and maybe error if it finds more than one, or zero).

We may want to support top-level queries too, like,

{ "@query-all": {"@type": "Person",
                 "name": {"@one-of": ["Alice", "Claire"]}},
  "@capture": "FoundPeople" }

{ "@type": "Person",
  "name": "Belle",
  "friends": {"@ref": "FoundPeople"}
}

cause this would allow reuse of a query result in multiple documents.

We may even want to support arbitrary woql queries, in which case we could even fill arbitrary fields with data that comes out of a query:

{ "@type": "Person",
  "name": {"@woql-one": {...}}
}

What do people think?