Major - P3 The _getLastDocID() function checks the last oplog entry of each shard to figure out the maxDocID. It's not guaranteed that the last oplog entry will be an insert of a document containing the docId field:
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] ----
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] Last docID: 167, lastEntries: [
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "op" : "u",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ns" : "config.cache.databases",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ui" : UUID("b3fb3e73-cc56-43fa-bbce-62362eaef69e"),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "$v" : 2,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "diff" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "u" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "version" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "uuid" : UUID("bf948bf4-90c6-46b3-9074-4b63668704ee"),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "timestamp" : Timestamp(0, 0),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "lastMod" : 0
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] }
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] }
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] }
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o2" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "_id" : "config"
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ts" : Timestamp(1654660031, 7),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "t" : NumberLong(1),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "v" : NumberLong(2),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "wall" : ISODate("2022-06-08T03:47:11.858Z")
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "op" : "i",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ns" : "test.continuous_writes_unrestored",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ui" : UUID("ca3f3e6f-d4ab-40ec-9d2d-b8ef968d94be"),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "_id" : ObjectId("62a01bbe4418e4e1315b8741"),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "shardId" : 1,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "numForPartition" : -50,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "docId" : 165
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o2" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "numForPartition" : -50,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "_id" : ObjectId("62a01bbe4418e4e1315b8741")
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ts" : Timestamp(1654660030, 16),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "t" : NumberLong(1),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "v" : NumberLong(2),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "wall" : ISODate("2022-06-08T03:47:11.012Z")
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "op" : "i",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ns" : "test.continuous_writes_unrestored",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ui" : UUID("ca3f3e6f-d4ab-40ec-9d2d-b8ef968d94be"),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "_id" : ObjectId("62a01bbf4418e4e1315b8745"),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "shardId" : 2,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "numForPartition" : 50,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "docId" : 166
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o2" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "numForPartition" : 50,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "_id" : ObjectId("62a01bbf4418e4e1315b8745")
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ts" : Timestamp(1654660031, 2),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "t" : NumberLong(1),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "v" : NumberLong(2),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "wall" : ISODate("2022-06-08T03:47:11.343Z")
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "op" : "i",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ns" : "test.continuous_writes_unrestored",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ui" : UUID("ca3f3e6f-d4ab-40ec-9d2d-b8ef968d94be"),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "_id" : ObjectId("62a01bbf4418e4e1315b8749"),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "shardId" : 3,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "numForPartition" : 150,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "docId" : 167
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o2" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "numForPartition" : 150,
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "_id" : ObjectId("62a01bbf4418e4e1315b8749")
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ts" : Timestamp(1654660031, 4),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "t" : NumberLong(1),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "v" : NumberLong(2),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "wall" : ISODate("2022-06-08T03:47:11.567Z")
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "op" : "n",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ns" : "",
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "o" : {
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "msg" : "periodic noop"
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] },
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "ts" : Timestamp(1654660031, 1),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "t" : NumberLong(1),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "v" : NumberLong(2),
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] "wall" : ISODate("2022-06-08T03:47:11.270Z")
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] }
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] ]
[js_test:sharded_pit_selective_backup_restore_simple] [jsTest] ----
As seen in the code snippet above, the first element of lastEntries is not an insert of a document with the docId field. We should filter for oplog entries containing docId and look at the last one then to properly compute the maxDocID.