資料結構一直改，MongoDB 能幫上什麼忙

What's new in this version:

Security:
- Ensure bind credentials live longer than LDAP operations

Sharding:
- Make allow_partial_results.js, return_partial_shards_down.js start shards as replica sets
make fsm workloads that extend kill_rooted_or.js more robust in the sharded concurrency suites, or blacklist them
- Add namespace to ChunkManager ShardKeyNotFound failure in order to better diagnose failures.
- Do not choose only first shard of all shards associated with a zone when pre-splitting during shard collection
- Make the BatchWriteExecutor retry multi-writes only against unsuccessful shards

Replication:
- ReplicationCoordinatorExternalState and data replication must not be started after shutdown
- Race while setting replication maintenance mode.
- Race in replsets/auth2.js
- fix the “me” field in isMaster responses when using splithorizon

Query:
- Aggregations and find commands sort missing fields differently
- Negation of inequality on array can trip invariant

Aggregation:
- Change stream should throw ChangeStreamFatalError if a single shard cannot be targeted for updateLookup
- Storage
- include Client/OpCtx information in LockManager::dump() output
- Adjust nojournal startup warning to be more compelling

Operations:
- Remove upstream metadata from v4.2’s third party library manifest
- Build and Packaging
- Remove mobile specific embedded commands
- Ubuntu 18.04 package testing task fails to install openssl

Internals:
- Relax expectations in apply_batches_totalMillis
- A stashed Locker should keep information about the owning transaction
- Refactor storage engine lock file support
- jstests/sharding/kill_sessions.js doesn’t wait for operation to be killed.
- Add a log line for when a cursor is reaped due to logical session cleanup
- Incorrect serialization for $elemMatch $not $ne
- Remove unused db_raii and server_status libs from storage_wiredtiger_core’s LIBDEPS_PRIVATE
- Correct logic to re-compute dependencies after absorbing a $sort into query layer
- Ensure RoleGraph can serialize authentication restrictions to BSON
- Fix strace in syscall test
- Reduce configuration parsing overhead from checkpoints
- Remove temporary files in clang-format script
- Handling goto labels with multiple words in s_goto.py
- Checkpoint hangs when reconciliation doesn’t release the eviction generation
- Adding new stats for eviction target strategy
- Change lookaside file inserts to use cursor.insert
- WT_REF_LIMBO pages cannot support fast (leaf-page only) searches
- Data mismatch failures with test/checkpoint after enabling LAS sweep
- Improve eviction to differentiate between clean and dirty pages with WT_CACHE_EVICT_NOKEEP readgen
- Fix syscall failure about metadata file open
- Ensure that only idempotent modify operations are logged
- Cursor key out-of-order detected in the lookaside file
- syscall.py fail on mongodb-4.0