bug: Panic with unique composite index on relation with filter on relation

[islamaliev]

Reported by @david-on-github

With this schema

type Foo {
  id: String
  bars: [Bar] @relation(name: "foobars")
}

type Bar @index(unique: true, includes: [{ name: "foo_id" }, { name: "id" }], name: "test_unqiue") {
  id: String
  foo: Foo @relation(name: "foobars")
}

Create some docs for them
Then try to query with a filter on the child relation

query {
  Foo {
    _docID
    bars(filter: { foo_id: {_eq: "bae-7eda71ae-2b1c-5ee8-9b21-d8e28b2bf8a3"} }) {
      _docID
      foo_id
    }
  }
}

Results in this panic.

panic: runtime error: invalid memory address or nil pointer dereference
 
 -> github.com/sourcenetwork/defradb/internal/db/fetcher.(*indexPrefixIterator).Close
 ->   github.com/sourcenetwork/defradb/internal/db/fetcher/indexer_iterators.go:144

    github.com/sourcenetwork/defradb/internal/db/fetcher.(*IndexFetcher).Close
      github.com/sourcenetwork/defradb/internal/db/fetcher/indexer.go:215
    github.com/sourcenetwork/defradb/internal/lens.(*lensedFetcher).Close
      github.com/sourcenetwork/defradb/internal/lens/fetcher.go:192
    github.com/sourcenetwork/defradb/internal/planner.(*scanNode).Close
      github.com/sourcenetwork/defradb/internal/planner/scan.go:229
    github.com/sourcenetwork/defradb/internal/planner.(*invertibleTypeJoin).Close
      github.com/sourcenetwork/defradb/internal/planner/type_join.go:491
    github.com/sourcenetwork/defradb/internal/planner.(*typeIndexJoin).Close
      github.com/sourcenetwork/defradb/internal/planner/type_join.go:132
    github.com/sourcenetwork/defradb/internal/planner.(*selectNode).Close
      github.com/sourcenetwork/defradb/internal/planner/select.go:189
    github.com/sourcenetwork/defradb/internal/planner.(*selectTopNode).Close
      github.com/sourcenetwork/defradb/internal/planner/select.go:89
    github.com/sourcenetwork/defradb/internal/planner.(*invertibleTypeJoin).Close
      github.com/sourcenetwork/defradb/internal/planner/type_join.go:495
    github.com/sourcenetwork/defradb/internal/planner.(*typeIndexJoin).Close
      github.com/sourcenetwork/defradb/internal/planner/type_join.go:132
    github.com/sourcenetwork/defradb/internal/planner.(*selectNode).Close
      github.com/sourcenetwork/defradb/internal/planner/select.go:189
    github.com/sourcenetwork/defradb/internal/planner.(*selectTopNode).Close
      github.com/sourcenetwork/defradb/internal/planner/select.go:89
    github.com/sourcenetwork/defradb/internal/planner.(*operationNode).Close
      github.com/sourcenetwork/defradb/internal/planner/operation.go:66
    github.com/sourcenetwork/defradb/internal/planner.(*Planner).RunRequest.func1
      github.com/sourcenetwork/defradb/internal/planner/planner.go:515
    github.com/sourcenetwork/defradb/internal/planner.(*Planner).RunRequest
      github.com/sourcenetwork/defradb/internal/planner/planner.go:545
    github.com/sourcenetwork/defradb/internal/db.(*db).execRequest
      github.com/sourcenetwork/defradb/internal/db/request.go:53
    github.com/sourcenetwork/defradb/internal/db.(*db).ExecRequest
      github.com/sourcenetwork/defradb/internal/db/store.go:38
    github.com/sourcenetwork/defradb/http.(*storeHandler).ExecRequest
      github.com/sourcenetwork/defradb/http/handler_store.go:311
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/go-chi/chi/v5.(*Mux).routeHTTP
      github.com/go-chi/chi/[email protected]/mux.go:459
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/go-chi/chi/v5.(*Mux).ServeHTTP
      github.com/go-chi/chi/[email protected]/mux.go:73
    github.com/sourcenetwork/defradb/http.(*Router).ServeHTTP
      github.com/sourcenetwork/defradb/http/router.go:67
    github.com/go-chi/chi/v5.(*Mux).routeHTTP
      github.com/go-chi/chi/[email protected]/mux.go:459
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/sourcenetwork/defradb/http.AuthMiddleware.func1
      github.com/sourcenetwork/defradb/http/auth.go:57
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/sourcenetwork/defradb/http.TransactionMiddleware.func1
      github.com/sourcenetwork/defradb/http/middleware.go:83
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/sourcenetwork/defradb/http.NewHandler.func1.ApiMiddleware.1.1
      github.com/sourcenetwork/defradb/http/middleware.go:71
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/go-chi/chi/v5.(*Mux).ServeHTTP
      github.com/go-chi/chi/[email protected]/mux.go:73
    github.com/go-chi/chi/v5.(*Mux).Mount.func1
      github.com/go-chi/chi/[email protected]/mux.go:327
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/go-chi/chi/v5.(*Mux).routeHTTP
      github.com/go-chi/chi/[email protected]/mux.go:459
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/go-chi/chi/v5.(*Mux).ServeHTTP
      github.com/go-chi/chi/[email protected]/mux.go:73
    github.com/sourcenetwork/defradb/http.(*Handler).ServeHTTP
      github.com/sourcenetwork/defradb/http/handler.go:107
    github.com/go-chi/chi/v5.(*Mux).routeHTTP
      github.com/go-chi/chi/[email protected]/mux.go:459
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/go-chi/cors.(*Cors).Handler-fm.(*Cors).Handler.func1
      github.com/go-chi/[email protected]/cors.go:228
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/go-chi/chi/v5/middleware.Recoverer.func1
      github.com/go-chi/chi/[email protected]/middleware/recoverer.go:45
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/sourcenetwork/defradb/http.NewServer.RequestLogger.func2.1
      github.com/go-chi/chi/[email protected]/middleware/logger.go:55
    net/http.HandlerFunc.ServeHTTP
      net/http/server.go:2171
    github.com/go-chi/chi/v5.(*Mux).ServeHTTP
      github.com/go-chi/chi/[email protected]/mux.go:90
    net/http.serverHandler.ServeHTTP
      net/http/server.go:3142
    net/http.(*conn).serve
      net/http/server.go:2044
    created by net/http.(*Server).Serve in goroutine 75
      net/http/server.go:3290