Secondary index on relation panics when querying

[AndrewSisley]

The following test panics:

func TestQueryWithIndexOnManyToOne_IfFilterOnIndexedRelation_ShouldFilterWithExplain2(t *testing.T) {
	test := testUtils.TestCase{
		Actions: []any{
			testUtils.SchemaUpdate{
				Schema: `
					type User {
						name: String
						devices: [Device]
					}

					type Device {
						model: String
						owner: User @index
						manufacturer: Manufacturer @index
					}

					type Manufacturer {
						name: String
						devices: [Device]
					}
				`,
			},
			testUtils.CreateDoc{
				DocMap: map[string]any{
					"name": "John",
				},
			},
			testUtils.CreateDoc{
				CollectionID: 2,
				DocMap: map[string]any{
					"name": "foo",
				},
			},
			testUtils.CreateDoc{
				CollectionID: 1,
				DocMap: map[string]any{
					"model":        "MacBook Pro",
					"owner":        testUtils.NewDocIndex(0, 0),
					"manufacturer": testUtils.NewDocIndex(2, 0),
				},
			},
			testUtils.Request{
				Request: `query {
					User {
						devices {
							owner_id
							manufacturer_id
						}
					}
				}`,
				Results: []map[string]any{},
			},
		},
	}

	testUtils.ExecuteTestCase(t, test)
}

panic: runtime error: index out of range [1] with length 1
	panic: Unclosed iterator at time of Txn.Discard. [recovered]
	panic: Unclosed iterator at time of Txn.Discard.

goroutine 39 [running]:
testing.tRunner.func1.2({0x411f8e0, 0x53e8fd0})
	/usr/local/go/src/testing/testing.go:1545 +0x238
testing.tRunner.func1()
	/usr/local/go/src/testing/testing.go:1548 +0x397
panic({0x411f8e0?, 0x53e8fd0?})
	/usr/local/go/src/runtime/panic.go:914 +0x21f
github.com/sourcenetwork/badger/v4.(*Txn).Discard(...)
	/home/andy/go/pkg/mod/github.com/sourcenetwork/badger/v4@v4.2.1-0.20231113215945-a63444ca5276/txn.go:524
github.com/sourcenetwork/defradb/datastore/badger/v4.(*txn).discard(...)
	/home/andy/Projects/Source/defradb/datastore/badger/v4/datastore.go:780
github.com/sourcenetwork/defradb/datastore/badger/v4.(*txn).Discard(0x2df5ee9?, {0x7d829e8?, 0x473cb01?})
	/home/andy/Projects/Source/defradb/datastore/badger/v4/datastore.go:776 +0x125
github.com/sourcenetwork/defradb/datastore.(*txn).Discard(0xc0013bc300, {0x543a8e0?, 0xc00131d2f0?})
	/home/andy/Projects/Source/defradb/datastore/txn.go:125 +0x32
panic({0x46a31a0?, 0xc001b7e198?})
	/usr/local/go/src/runtime/panic.go:914 +0x21f
github.com/sourcenetwork/defradb/internal/db/fetcher.(*IndexFetcher).newIndexDataStoreKeyWithValues(0xc001e85880, {0xc001b821a0, 0x2, 0x20?})
	/home/andy/Projects/Source/defradb/internal/db/fetcher/indexer_iterators.go:530 +0xe9
github.com/sourcenetwork/defradb/internal/db/fetcher.(*IndexFetcher).newPrefixIndexIterator(0xc001e85880, {0xc001b86660, 0x2, 0x31313131?}, {0xc001b82180, 0x2, 0x2})
	/home/andy/Projects/Source/defradb/internal/db/fetcher/indexer_iterators.go:457 +0x1af
github.com/sourcenetwork/defradb/internal/db/fetcher.(*IndexFetcher).createIndexIterator(0xc001e85880)
	/home/andy/Projects/Source/defradb/internal/db/fetcher/indexer_iterators.go:561 +0x147
github.com/sourcenetwork/defradb/internal/db/fetcher.(*IndexFetcher).Init(0xc001e85880, {0x543a8e0, 0xc00131d2f0}, {0x0, {0x0, 0x0, {0x0, 0x0}, {0x0, 0x0}}}, ...)
	/home/andy/Projects/Source/defradb/internal/db/fetcher/indexer.go:95 +0x619
github.com/sourcenetwork/defradb/internal/lens.(*lensedFetcher).Init(0xc00112e7e0, {0x543a8e0?, 0xc00131d2f0}, {0x0, {0x0, 0x0, {0x0, 0x0}, {0x0, 0x0}}}, ...)
	/home/andy/Projects/Source/defradb/internal/lens/fetcher.go:115 +0xcad
github.com/sourcenetwork/defradb/internal/planner.(*scanNode).Init(0xc001aba540)
	/home/andy/Projects/Source/defradb/internal/planner/scan.go:65 +0x17e
github.com/sourcenetwork/defradb/internal/planner.(*multiScanNode).Init(0x13?)
	/home/andy/Projects/Source/defradb/internal/planner/scan.go:335 +0x16
github.com/sourcenetwork/defradb/internal/planner.(*invertibleTypeJoin).Init(0xc00795c000)
	/home/andy/Projects/Source/defradb/internal/planner/type_join.go:480 +0x48
github.com/sourcenetwork/defradb/internal/planner.(*typeIndexJoin).Init(0xc00794a0c0?)
	/home/andy/Projects/Source/defradb/internal/planner/type_join.go:110 +0x1c
github.com/sourcenetwork/defradb/internal/planner.(*parallelNode).Init.func1(...)
	/home/andy/Projects/Source/defradb/internal/planner/multi.go:83
github.com/sourcenetwork/defradb/internal/planner.(*parallelNode).applyToPlans(...)
	/home/andy/Projects/Source/defradb/internal/planner/multi.go:70
github.com/sourcenetwork/defradb/internal/planner.(*parallelNode).Init(0x1?)
	/home/andy/Projects/Source/defradb/internal/planner/multi.go:82 +0x51
github.com/sourcenetwork/defradb/internal/planner.(*selectNode).Init(0x1?)
	/home/andy/Projects/Source/defradb/internal/planner/select.go:138 +0x1c
github.com/sourcenetwork/defradb/internal/planner.(*selectTopNode).Init(0xc000f71128?)
	/home/andy/Projects/Source/defradb/internal/planner/select.go:66 +0x1c
github.com/sourcenetwork/defradb/internal/planner.(*primaryObjectsRetriever).collectDocs(0xc00795a101?, 0x0)
	/home/andy/Projects/Source/defradb/internal/planner/type_join.go:562 +0x3d
github.com/sourcenetwork/defradb/internal/planner.(*primaryObjectsRetriever).retrievePrimaryDocs(0xc00788a0c0)
	/home/andy/Projects/Source/defradb/internal/planner/type_join.go:596 +0x3dc
github.com/sourcenetwork/defradb/internal/planner.(*primaryObjectsRetriever).retrievePrimaryDocsReferencingSecondaryDoc(0xc00788a0c0)
	/home/andy/Projects/Source/defradb/internal/planner/type_join.go:536 +0x210
github.com/sourcenetwork/defradb/internal/planner.(*invertibleTypeJoin).fetchPrimaryDocsReferencingSecondaryDoc(0x0?)
	/home/andy/Projects/Source/defradb/internal/planner/type_join.go:655 +0xa7
github.com/sourcenetwork/defradb/internal/planner.(*invertibleTypeJoin).Next(0xc00795c2c0)
	/home/andy/Projects/Source/defradb/internal/planner/type_join.go:681 +0x119
github.com/sourcenetwork/defradb/internal/planner.(*typeIndexJoin).Next(0xc00788a2b0?)
	/home/andy/Projects/Source/defradb/internal/planner/type_join.go:124 +0x22
github.com/sourcenetwork/defradb/internal/planner.(*selectNode).Next(0xc001e8a000)
	/home/andy/Projects/Source/defradb/internal/planner/select.go:153 +0x3c
github.com/sourcenetwork/defradb/internal/planner.(*selectTopNode).Next(0xc000fdc0b0?)
	/home/andy/Projects/Source/defradb/internal/planner/select.go:70 +0x1c
github.com/sourcenetwork/defradb/internal/planner.(*Planner).executeRequest(0x0?, {0x4087d00?, 0xc001326a50?}, {0x5458408, 0xc007950be0})
	/home/andy/Projects/Source/defradb/internal/planner/planner.go:538 +0x4e
github.com/sourcenetwork/defradb/internal/planner.(*Planner).RunRequest(0x543a8e0?, {0x543a8e0, 0xc00131d2f0}, 0xc001326a50)
	/home/andy/Projects/Source/defradb/internal/planner/planner.go:593 +0x2c9
github.com/sourcenetwork/defradb/internal/db.(*db).execRequest(0xc001dd40c0, {0x543a8e0, 0xc00131d2f0}, {0x4b0a055, 0x5f})
	/home/andy/Projects/Source/defradb/internal/db/request.go:53 +0x426
github.com/sourcenetwork/defradb/internal/db.(*db).ExecRequest(0x0?, {0x543a8e0?, 0xc00131d230?}, {0x4b0a055, 0x5f})
	/home/andy/Projects/Source/defradb/internal/db/store.go:33 +0x1b3
github.com/sourcenetwork/defradb/tests/integration.executeRequest(0xc0012e7440, {{0x0, 0x0}, {0x0, 0x0}, {0x0, 0x0}, {0x4b0a055, 0x5f}, {0x7ec4280, ...}, ...})
	/home/andy/Projects/Source/defradb/tests/integration/utils2.go:1686 +0x1d6
github.com/sourcenetwork/defradb/tests/integration.performAction(0xc0012e7440, 0x0?, {0x4702700?, 0xc001812d00?})
	/home/andy/Projects/Source/defradb/tests/integration/utils2.go:333 +0x8e5
github.com/sourcenetwork/defradb/tests/integration.executeTestCase({0x543a870?, 0x7ec4280}, {0x548cf18?, 0xc001d02b60?}, {0xc000b2b440, 0x3, 0x3}, {{0x0, 0x0}, {0xc00169ac80, ...}, ...}, ...)
	/home/andy/Projects/Source/defradb/tests/integration/utils2.go:226 +0xeab
github.com/sourcenetwork/defradb/tests/integration.ExecuteTestCase({0x548cf18?, 0xc001d02b60}, {{0x0, 0x0}, {0xc00169ac80, 0x5, 0x5}, {0x0, {0x0, 0x0, ...}}, ...})
	/home/andy/Projects/Source/defradb/tests/integration/utils2.go:180 +0x608
github.com/sourcenetwork/defradb/tests/integration/index.TestQueryWithIndexOnManyToOne_IfFilterOnIndexedRelation_ShouldFilterWithExplain2(0x0?)
	/home/andy/Projects/Source/defradb/tests/integration/index/query_with_relation_filter_test.go:969 +0x587
testing.tRunner(0xc001d02b60, 0x4da9a78)
	/usr/local/go/src/testing/testing.go:1595 +0xff
created by testing.(*T).Run in goroutine 1
	/usr/local/go/src/testing/testing.go:1648 +0x3ad

It does not panic if any of the query fields are omitted.