I'm pleased to announce version 1.15.0 of libbson and libmongoc,
the libraries constituting the MongoDB C Driver.

libbson

No change since 1.14.1; released to keep pace with libmongoc's version.

libmongoc

It is my pleasure to announce the MongoDB C Driver 1.15.0. This release adds
support for MongoDB 4.2 features.

Features:

Support for sharded transactions on MongoDB sharded clusters 4.2+.
Add convenient transaction runner (mongoc_client_session_with_transaction),
which accepts a callback and performs appropriate retry logic.
Add a new transaction option to specify maximum time to wait for a commit,
mongoc_transaction_opts_set_max_commit_time_ms.
Add URI option "retryReads=true" safely and automatically retries certain
read operations if the server is a MongoDB 3.6+. Note, this may require applications to adjust any custom retry logic to prevent inadvertently retrying for too long
Poll SRV records to mongos servers periodically.
Keep connections alive after a primary stepdown detected.
Standardizes URI options supported across all spec-compliant MongoDB drivers.
"retryWrites" URI option now defaults to true (requires crypto for session
support).
Send any aggregate with $out or $merge stage to a primary.
Add the ability to specify an aggregate pipeline as an update document.
Add a database aggregate helper, mongoc_database_aggregate.
Add option for change streams, "startAfter".
Add mongoc_change_stream_get_resume_token, which returns the resume token
which should be used to resume a change stream.
Add support for zstd compression.

Bug fixes:

Correctly report an error in mongoc_change_stream_next if the resume token
(_id) is not a document. Previously, an error was only reported if the
field was missing.
Fix mongoc_collection_update with MONGOC_UPDATE_MULTI_UPDATE,
mongoc_collection_remove, and mongoc_collection_delete when retryWrites
was enabled. They would fail previously.
Command options are now correctly taken into account when batching bulk
writes for OP_QUERY. It was possible to exceed the maximum document size
before.
Fix a crash if a multi-batch bulk write with OP_MSG errored on a batch.