CSHARP-2043: Add AssumeIndexesExist option to GridFSBucketOptions by papafe · Pull Request #2047 · mongodb/mongo-csharp-driver

papafe · 2026-06-23T13:14:44Z

Adds a AssumeIndexesExist option to GridFSBucketOptions that lets users opt out of the automatic GridFS index check and creation on the first upload.

Based on the original contribution by John Gibbons (@jg11jg) in #294, updated for the current src/MongoDB.Driver/ project layout and with added coverage. Supersedes #292 and #294.

Lets users opt out of the automatic GridFS index check and creation on first upload. Useful for sharded clusters (where the empty-files check is broadcast to all shards and fails if any shard is down) and write-only users. Based on the original work by John Gibbons (jg11jg) in mongodb#294.

Copilot

Pull request overview

Adds a new AssumeIndexesExist option to GridFS bucket configuration so callers can opt out of the driver’s automatic GridFS index check/creation that normally occurs before the first upload.

Changes:

Introduces AssumeIndexesExist on GridFSBucketOptions / ImmutableGridFSBucketOptions.
Skips EnsureIndexes / EnsureIndexesAsync in GridFSBucket when AssumeIndexesExist is enabled.
Adds/updates unit + integration tests to validate option behavior and defaults.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
`src/MongoDB.Driver/GridFS/GridFSBucketOptions.cs`	Adds `AssumeIndexesExist` to mutable/immutable options and copies it through constructors.
`src/MongoDB.Driver/GridFS/GridFSBucket.cs`	Early-returns from index ensure paths when `AssumeIndexesExist` is true.
`tests/MongoDB.Driver.Tests/GridFS/GridFSBucketTests.cs`	Adds integration coverage asserting index creation is skipped/enabled based on the option.
`tests/MongoDB.Driver.Tests/GridFS/GridFSBucketOptionsTests.cs`	Adds unit coverage for the new option and ensures it round-trips through constructors/defaults.

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…tion - ImmutableGridFSBucketOptions defaults test now constructs the immutable type. - Assert GridFS index absence rather than OnlyContain(_id_) to avoid flakiness.

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

+            RequireServer.Check();
+            var client = DriverTestConfiguration.Client;
+            var database = client.GetDatabase(DriverTestConfiguration.DatabaseNamespace.DatabaseName);
+            var options = new GridFSBucketOptions { AssumeIndexesExist = true };
+            var subject = new GridFSBucket(database, options);
+            subject.Drop();
+
+            if (async)
+            {
+                subject.UploadFromBytesAsync("filename", new byte[] { 0 }).GetAwaiter().GetResult();
+            }
+            else
+            {
+                subject.UploadFromBytes("filename", new byte[] { 0 });
+            }
+
+            var filesIndexes = database.GetCollection<BsonDocument>("fs.files").Indexes.List().ToList();
+            filesIndexes.Should().NotContain(index => index["name"] == "filename_1_uploadDate_1");
+            var chunksIndexes = database.GetCollection<BsonDocument>("fs.chunks").Indexes.List().ToList();
+            chunksIndexes.Should().NotContain(index => index["name"] == "files_id_1_n_1");
+        }


+            RequireServer.Check();
+            var client = DriverTestConfiguration.Client;
+            var database = client.GetDatabase(DriverTestConfiguration.DatabaseNamespace.DatabaseName);
+            var subject = new GridFSBucket(database);
+            subject.Drop();
+
+            if (async)
+            {
+                subject.UploadFromBytesAsync("filename", new byte[] { 0 }).GetAwaiter().GetResult();
+            }
+            else
+            {
+                subject.UploadFromBytes("filename", new byte[] { 0 });
+            }
+
+            var filesIndexes = database.GetCollection<BsonDocument>("fs.files").Indexes.List().ToList();
+            filesIndexes.Should().Contain(index => index["name"] == "filename_1_uploadDate_1");
+            var chunksIndexes = database.GetCollection<BsonDocument>("fs.chunks").Indexes.List().ToList();
+            chunksIndexes.Should().Contain(index => index["name"] == "files_id_1_n_1");
+        }


+        /// <summary>
+        /// Gets or sets whether to assume the GridFS indexes already exist, skipping the index check and creation before the first upload.
+        /// </summary>


+        /// <summary>
+        /// Gets whether to assume the GridFS indexes already exist, skipping the index check and creation before the first upload.
+        /// </summary>


Upload_should_not_create_indexes_when_AssumeIndexesExist_is_true left the shared fs.files/fs.chunks non-empty without the GridFS indexes. A later test sharing the same bucket (Upload_of_duplicate_file_should_not_invalidate_existing_data) then found a non-empty files collection, so EnsureIndexes skipped index creation, and the missing unique {files_id:1,n:1} index meant the expected duplicate-key MongoBulkWriteException was never thrown. Drop the bucket at the end of the test to leave the collections empty.

Wrap the AssumeIndexesExist integration tests in try/finally and drop the bucket in the finally block (async-aware via a DropBucket helper) so shared fs.* state is restored even if an assertion fails.

Add a remarks block warning that when true the driver never verifies or creates the GridFS indexes, so the caller must ensure they exist.

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

ajcvickers · 2026-06-24T11:41:51Z

+            if (_options.AssumeIndexesExist)
+            {
+                return;
+            }


Not a bug: the binding is acquired via GetSingleServerReadWriteBinding(operationContext) before EnsureIndexes is reached, so server selection already observes the caller's token/deadline, and the upload's chunk/file inserts observe it downstream — the skipped semaphore-wait was only an incidental cancellation checkpoint, so cancellation is still surfaced.

ajcvickers · 2026-06-24T11:42:07Z

+            if (_options.AssumeIndexesExist)
+            {
+                return;
+            }


Same as the sync path.

…ync theory Per review feedback, merge the two index-behavior integration tests into a single async Task theory parameterized over assumeIndexesExist, using await instead of GetAwaiter().GetResult(). DropBucket helper is now async.

sanych-sun

LGTM + minor comment for your consideration.

sanych-sun · 2026-06-25T23:31:59Z

+            var database = client.GetDatabase(DriverTestConfiguration.DatabaseNamespace.DatabaseName);
+            var options = new GridFSBucketOptions { AssumeIndexesExist = assumeIndexesExist };
+            var subject = new GridFSBucket(database, options);
+            await DropBucketAsync(subject, async);


Minor: I would say we can use async api for setup/clean up. There is no perks in executing sync code for setup.

Copilot AI review requested due to automatic review settings June 23, 2026 13:14

papafe requested a review from a team as a code owner June 23, 2026 13:14

papafe requested a review from ajcvickers June 23, 2026 13:14

Copilot started reviewing on behalf of papafe June 23, 2026 13:15 View session

papafe added the feature Adds new user-facing functionality. label Jun 23, 2026

This was referenced Jun 23, 2026

CSHARP-2043: Added AssumeIndexesExist option to improve robustness of sharded GridFS #294

Closed

CSHARP-2043: Added SuppressEnsureIndexes option to GridFSBucketOption… #292

Closed

Copilot AI reviewed Jun 23, 2026

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Comment thread tests/MongoDB.Driver.Tests/GridFS/GridFSBucketOptionsTests.cs

Comment thread tests/MongoDB.Driver.Tests/GridFS/GridFSBucketTests.cs Outdated

Address PR review: fix immutable defaults test and loosen index asser…

b5c1d6e

…tion - ImmutableGridFSBucketOptions defaults test now constructs the immutable type. - Assert GridFS index absence rather than OnlyContain(_id_) to avoid flakiness.

papafe requested a review from Copilot June 23, 2026 13:36

Copilot started reviewing on behalf of papafe June 23, 2026 13:37 View session

Copilot AI reviewed Jun 23, 2026

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papafe added 2 commits June 23, 2026 18:54

Address PR review: clean up GridFS buckets in finally for test isolation

c9a7a6c

Wrap the AssumeIndexesExist integration tests in try/finally and drop the bucket in the finally block (async-aware via a DropBucket helper) so shared fs.* state is restored even if an assertion fails.

papafe requested a review from Copilot June 23, 2026 18:25

Copilot started reviewing on behalf of papafe June 23, 2026 18:26 View session

Address PR review: document AssumeIndexesExist index responsibility

4f01a35

Add a remarks block warning that when true the driver never verifies or creates the GridFS indexes, so the caller must ensure they exist.

Copilot AI reviewed Jun 23, 2026

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ajcvickers approved these changes Jun 24, 2026

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sanych-sun reviewed Jun 24, 2026

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Comment thread tests/MongoDB.Driver.Tests/GridFS/GridFSBucketTests.cs Outdated

Comment thread tests/MongoDB.Driver.Tests/GridFS/GridFSBucketTests.cs Outdated

papafe requested a review from sanych-sun June 25, 2026 08:20

sanych-sun approved these changes Jun 25, 2026

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CSHARP-2043: Add AssumeIndexesExist option to GridFSBucketOptions#2047

CSHARP-2043: Add AssumeIndexesExist option to GridFSBucketOptions#2047
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