feat(csharp): native C# Snowflake ADBC driver (REST-based) by ndglover · Pull Request #171 · adbc-drivers/snowflake

ndglover · 2026-07-14T14:27:47Z

Adds a from-scratch, fully-managed C# implementation of the Snowflake ADBC driver (net8.0), independent of the Go/cgo Interop driver. It speaks Snowflake's internal REST protocol directly and returns Arrow natively.

As discussed in our slack chat here is a first cut of the driver.

Tagging @lidavidm @ianmcook @davidhcoe @CurtHagenlocher

lidavidm · 2026-07-29T02:24:10Z

I thought certain IDE files used CRLF?

I found that by not fixing it to one or the other you end up with certain IDEs automatically modifying the files. This means you need to manually handle this in git by reverting these changes or you end up in ding dong between different conventions people have. I believe fixing to one works better but open to other suggestions

CurtHagenlocher · 2026-07-29T02:59:42Z

Thanks @lidavidm for leaving a comment which reminded me of this PR. I'll set some time aside tomorrow evening to look at it. There are a bunch of linter issues around whitespace and at least one file missing a copyright notice. I also wonder whether the copyright year should be 2026 ;). And this is probably just a "me" thing, but I find I keep getting confused by the use of "Native" to refer to the managed implementation (being "native C#").

lidavidm · 2026-07-29T03:08:05Z

+        ArgumentNullException.ThrowIfNull(batch);
+        ArgumentNullException.ThrowIfNull(schema);
+
+        _boundParameters = batch;


If _boundParameters is already set, should we dispose it?

Agreed, I've fixed this now

lidavidm · 2026-07-29T03:09:07Z

+        if (parameters.TryGetValue("adbc.snowflake.sql.client_option.request_timeout", out string? requestTimeoutStr) &&
+            int.TryParse(requestTimeoutStr, out int requestTimeoutSeconds))
+        {
+            config.QueryTimeout = TimeSpan.FromSeconds(requestTimeoutSeconds);
+        }


If the value is present but does not parse, presumably we should error?

Yes, this is a better pattern, thanks. I've applied a fix

Adds a from-scratch, fully-managed C# implementation of the Snowflake ADBC driver (net8.0), independent of the Go/cgo Interop driver. It speaks Snowflake's internal REST protocol directly and returns Arrow natively. Add QueryTag to connection and statement

…ring them

ndglover · 2026-07-31T15:41:24Z

@CurtHagenlocher - I think I've fixed up the linting issues and missing license headers now.
@lidavidm - that's for your comments, these are all fixed as well now

Copilot

Pull request overview

Adds a new, fully-managed native C# Snowflake ADBC driver (net8.0) that speaks Snowflake’s REST protocol directly and returns Arrow results natively, plus a comprehensive unit/integration test suite and related developer tooling.

Changes:

Introduces the core native driver surface (SnowflakeDriver, SnowflakeDatabase) and supporting services (authentication, transport, query execution, connection pooling).
Adds extensive offline unit tests for protocol/shape handling and correctness, plus opt-in live integration tests and benchmarks.
Adds C# workspace tooling/config updates (.editorconfig, ignore rules) and benchmark runner script.

Reviewed changes

Copilot reviewed 100 out of 101 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
csharp/test/Native/SnowflakeResultArrowStreamTests.cs	Offline tests for Arrow result stream fixups (FIXED/TIME/TIMESTAMP handling).
csharp/test/Native/SnowflakeDriverTests.cs	Unit tests for driver open/parameter validation behavior.
csharp/test/Native/SnowflakeDatabaseTests.cs	Unit tests for HttpMessageHandler ownership/disposal semantics.
csharp/test/Native/SnowflakeConnectionTransactionTests.cs	Unit tests for autocommit/transaction control and pool-safe cleanup.
csharp/test/Native/SnowflakeAccountUrlTests.cs	Unit tests for account/base URL building behavior.
csharp/test/Native/RequestBuilderTests.cs	Unit tests for query/cancel request body construction.
csharp/test/Native/QueryExecutorTests.cs	Unit tests for DML affected-row detection and envelope classification helpers.
csharp/test/Native/QueryExecutorInProgressTests.cs	Unit tests for long-running query polling and session-renewal during polling.
csharp/test/Native/QueryExecutorHeartbeatTests.cs	Unit tests for heartbeat behavior and renewal fallback.
csharp/test/Native/QueryExecutorFaultTests.cs	Unit tests for connection-fault callback rules across failure modes.
csharp/test/Native/QueryExecutorEmptyResultTests.cs	Unit tests for zero-row Arrow result handling and schema construction.
csharp/test/Native/KeyPairAuthenticatorTests.cs	Unit tests for key-pair JWT auth and key-material resolution/validation.
csharp/test/Native/Integration/SessionRenewalTests.cs	Live tests for session renewal and heartbeat endpoints.
csharp/test/Native/Integration/IntegrationTestingUtils.cs	Integration test configuration loading + parameter mapping helpers.
csharp/test/Native/Integration/IntegrationTestConfiguration.cs	Integration test config model (interop-compatible JSON shape).
csharp/test/Native/Integration/ConnectionTests.cs	Live connectivity/lifecycle smoke tests for the native driver.
csharp/test/Native/Integration/BenchmarkTests.cs	Live benchmark test (native driver) mirroring interop benchmark shape.
csharp/test/Native/ConnectionPool/PooledConnectionTests.cs	Unit tests for pooled token-expiry tracking via injected clock.
csharp/test/Native/ChunkedArrowArrayStreamTests.cs	Unit tests for chunk prefetch windowing/backpressure and disposal.
csharp/test/Native/BindCases.cs	Central bind-case catalog shared by offline/live bind tests.
csharp/test/Native/AdbcDrivers.Snowflake.Native.Tests.csproj	New native driver test project and dependencies.
csharp/test/Interop/SnowflakeTestConfiguration.cs	Minor formatting update in interop test configuration model.
csharp/test/Interop/BenchmarkTests.cs	Interop benchmark test file (mirrors native benchmark shape).
csharp/src/Native/SnowflakeDriver.cs	Native ADBC driver entry point (`Open`).
csharp/src/Native/SnowflakeDatabase.cs	Database implementation (HttpClient creation, pooling, Connect/Dispose).
csharp/src/Native/Services/TypeConversion/SnowflakeTypeCode.cs	Snowflake type code enum.
csharp/src/Native/Services/TypeConversion/SnowflakeDataType.cs	Snowflake type metadata model + type-name parsing.
csharp/src/Native/Services/TypeConversion/ParameterSet.cs	Bind parameter set model for positional parameters.
csharp/src/Native/Services/TypeConversion/ITypeConverter.cs	Type conversion interface (Snowflake→Arrow and Arrow→binds).
csharp/src/Native/Services/Transport/SnowflakeRequestBodies.cs	Query/cancel/renew request models + binding JSON converter.
csharp/src/Native/Services/Transport/SnowflakeProtocolConstants.cs	Protocol constants (session parameter keys/values, bind type names).
csharp/src/Native/Services/Transport/SnowflakeJsonContext.cs	Source-generated JSON serializer context for query protocol types.
csharp/src/Native/Services/Transport/RequestBuilder.cs	Builder for query and cancel request bodies.
csharp/src/Native/Services/Transport/IRestApiClient.cs	REST client abstraction for POST/GET and Arrow chunk streams.
csharp/src/Native/Services/Transport/ApiResponse.cs	Generic Snowflake API response envelope model.
csharp/src/Native/Services/SnowflakeAccountUrl.cs	Base account URL builder supporting host/protocol/port overrides.
csharp/src/Native/Services/Session/SnowflakeSessionClient.cs	Pool-facing session lifecycle implementation (heartbeat/close).
csharp/src/Native/Services/Query/SnowflakeQueryResponse.cs	Query response wire model (rowtype/rowset/chunks, result URL).
csharp/src/Native/Services/Query/QueryStatus.cs	Query status enum.
csharp/src/Native/Services/Query/QueryResult.cs	Query result model (stream, row count, affected rows, errors).
csharp/src/Native/Services/Query/QueryRequest.cs	Query request model (statement/session context/binds/timeouts).
csharp/src/Native/Services/Query/QueryError.cs	Query error model (code/message/exception).
csharp/src/Native/Services/Query/PreparedStatement.cs	Prepared statement model (result schema only).
csharp/src/Native/Services/Query/IQueryExecutor.cs	Query execution interface (execute/describe/renew/heartbeat/cancel).
csharp/src/Native/Services/Query/EmptyArrowArrayStream.cs	Empty Arrow stream implementation carrying schema only.
csharp/src/Native/Services/Query/ChunkedArrowArrayStream.cs	Arrow result streaming over inline+chunked data with prefetching.
csharp/src/Native/Services/ConnectionPool/PooledConnection.cs	Pooled connection implementation (token expiry, timestamps, close).
csharp/src/Native/Services/ConnectionPool/ISessionLifecycle.cs	Pool callback interface for heartbeat/close over transport layer.
csharp/src/Native/Services/ConnectionPool/IPooledConnection.cs	Pooled connection interface (timestamps, token, faulting, lifecycle).
csharp/src/Native/Services/ConnectionPool/IConnectionPoolManager.cs	Pool manager interface (acquire/release).
csharp/src/Native/Services/ConnectionPool/ConnectionPoolEntry.cs	Pool entry state (active/idle collections, capacity semaphore).
csharp/src/Native/Services/Authentication/SnowflakeLoginClient.cs	Login/close-session client using Snowflake login protocol.
csharp/src/Native/Services/Authentication/PatAuthenticator.cs	PAT authentication implementation and requirement validation.
csharp/src/Native/Services/Authentication/OAuthAuthenticator.cs	OAuth authentication implementation and requirement validation.
csharp/src/Native/Services/Authentication/LoginResponseModels.cs	Login/authenticator response models.
csharp/src/Native/Services/Authentication/LoginRequestModels.cs	Login request models (web-default JSON naming).
csharp/src/Native/Services/Authentication/KeyPairAuthenticator.cs	Key-pair JWT auth implementation + key resolution helpers.
csharp/src/Native/Services/Authentication/ISsoAuthenticator.cs	SSO authenticator interface.
csharp/src/Native/Services/Authentication/IPatAuthenticator.cs	PAT authenticator interface.
csharp/src/Native/Services/Authentication/IOAuthAuthenticator.cs	OAuth authenticator interface.
csharp/src/Native/Services/Authentication/IKeyPairAuthenticator.cs	Key-pair authenticator interface.
csharp/src/Native/Services/Authentication/IBasicAuthenticator.cs	Username/password authenticator interface.
csharp/src/Native/Services/Authentication/IAuthenticationService.cs	Authentication service interface.
csharp/src/Native/Services/Authentication/ClientEnvironment.cs	Client environment payload model for login.
csharp/src/Native/Services/Authentication/BasicAuthenticator.cs	Username/password auth implementation and requirement validation.
csharp/src/Native/Services/Authentication/AuthenticationToken.cs	Token model (session + master validity windows).
csharp/src/Native/Services/Authentication/AuthenticationService.cs	Auth dispatcher by configured authentication type.
csharp/src/Native/InMemoryArrowStream.cs	In-memory Arrow stream for metadata-style prebuilt batches.
csharp/src/Native/Configuration/NetworkConfig.cs	Network config (host/protocol/port/proxy/TLS skip verify).
csharp/src/Native/Configuration/ConnectionPoolConfig.cs	Pool sizing/timeouts configuration model.
csharp/src/Native/Configuration/ConnectionConfig.cs	Connection config model (auth/network/pool/timeouts/keep-alive).
csharp/src/Native/Configuration/AuthenticationType.cs	Authentication type enum.
csharp/src/Native/Configuration/AuthenticationConfig.cs	Authentication config model (password/key/token/SSO props).
csharp/src/Native/AdbcDrivers.Snowflake.Native.csproj	Native driver project definition and packaging metadata.
csharp/run_benchmark.ps1	Script to run and compare native vs interop benchmarks and summarize stats.
csharp/.gitignore	C# workspace ignore updates (IDE artifacts).
csharp/.editorconfig	C# workspace EditorConfig (layout rules + silent style hints).
.gitignore	Repo-level ignore updates for Go shared library artifacts.
.gitattributes	Repo-level text/eol normalization settings.

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ndglover · 2026-09-09T08:27:21Z

+        var protocol = network?.Protocol ?? "https";
+        var host = account.Contains("snowflakecomputing.com", System.StringComparison.OrdinalIgnoreCase)
+            ? account
+            : $"{account}.snowflakecomputing.com";
+        var portSuffix = (network != null && network.Port != 443) ? $":{network.Port}" : string.Empty;
+        return $"{protocol}://{host}{portSuffix}";


I've made some changes to make it more robust and take into account different region and cloud suffixes

ndglover · 2026-09-09T08:28:23Z

+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="9.0.0" />
+    <PackageReference Include="Microsoft.Extensions.TimeProvider.Testing" Version="9.0.0" />


I'm leaving this for now, it's minor and will be better fixed when we pull the latest arrow packages with different transitive dependencies

ndglover · 2026-09-09T08:29:26Z

+        AuthenticationType.UsernamePassword => auth.Password,
+        AuthenticationType.OAuth or AuthenticationType.Pat => auth.Token,
+        AuthenticationType.KeyPair => $"{auth.PrivateKey ?? auth.PrivateKeyPath}{auth.PrivateKeyPassphrase}",
+        _ => null,


Created CredentialFieldDelimiter

CurtHagenlocher

I've taken a pass over all the files and left a random assortment of comments. Looks good overall; I don't think there's anything that critically needs to be changed but I do have some suggestions for things that (I think :) would be improvements.

After the first two hours, I stopped focusing on the Snowflake-specific stuff and focused on the Arrow-specific code where I probably add more value anyway.

CurtHagenlocher · 2026-09-01T15:31:43Z

@@ -0,0 +1,64 @@
+/*
+* Copyright (c) 2025 ADBC Drivers Contributors


It's closer to 2027 than 2025 ;)

Agreed, updated :-)

CurtHagenlocher · 2026-09-01T15:32:11Z

        /// </summary>
        [JsonPropertyName("roleInfo")]
        public RoleInfo? RoleInfo { get; set; }
+


nit: any reason for the added whitespace?

CurtHagenlocher · 2026-09-01T15:36:15Z

 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{827E0CD3-B72D-47B6-A68D-7590B98EB39B}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Native", "Native", "{986E768A-9E42-6229-8E82-349DB5D13BDD}"


I find the use of "native" to mean "natively C#" a bit confusing. In the context of .NET it's usually used to mean the opposite of "managed" -- at least in my world; maybe this isn't common?

See for example https://github.com/adbc-drivers/hiveserver2/tree/main/csharp/src and https://github.com/CurtHagenlocher/bigquery/tree/curth_microsoft/aot-clast-packages/csharp/src (which, to be fair, are me) but also https://github.com/lomakinandrei/NativeWPF and https://github.com/3F/Conari and even https://learn.microsoft.com/en-us/dotnet/core/deploying/native-aot -- not to belabor the point ;).

CurtHagenlocher · 2026-09-01T16:06:05Z

+        return typeName.ToUpperInvariant() switch
+        {
+            "FIXED" or "NUMBER" or "DECIMAL" or "NUMERIC" => SnowflakeTypeCode.Number,
+            "INTEGER" or "INT" or "BIGINT" or "SMALLINT" or "TINYINT" or "BYTEINT" => SnowflakeTypeCode.Integer,


Not really a review comment, but I'm curious -- under what circumstances Snowflake will return one of these type names?

Good spot, I included the DML types which never get returned. I took a closer look at the types and mapping and have made this more robust with added integration test,

CurtHagenlocher · 2026-09-01T16:12:37Z

+            SnowflakeTypeCode.TimestampLtz => new TimestampType(TimeUnit.Nanosecond, timezone: "UTC"),
+
+            // The result decoder stores TIMESTAMP_TZ as its UTC instant (a single Arrow column
+            // cannot carry a per-row offset), so the described type matches: Timestamp[ns] "UTC".


FWIW, in arrow-dotnet 23 there's an Arrow extension type that stores the rough equivalent of a .NET DateTimeOffset. It's TimestampWithOffsetType.

Need to upgrade to v23, I'll tackle in subsequent PR

CurtHagenlocher · 2026-09-02T03:18:07Z

+            if (!responseContent.Success)
+            {
+                var errorMessage = responseContent.Message ?? "Authentication failed.";
+                throw new AdbcException($"Snowflake authentication failed: {errorMessage}");


In general, it would be nice to try to assign an AdbcStatusCode to the exceptions. This is particularly true for authentication-related exceptions, which a consumer has no way to distinguish from other kinds of exceptions except by examining the text.

Added the status code now

CurtHagenlocher · 2026-09-02T03:37:24Z

+            var first = chunkList[0];
+            chunkList.RemoveAt(0);
+            firstStream = await apiClient.GetArrowStreamAsync(first.Url, authToken, chunkHeaders, qrmk, cancellationToken).ConfigureAwait(false);
+            firstReader = new Ipc.ArrowStreamReader(firstStream);


You should be able to pass a byte[] directly to the constructor of an ArrowStreamReader; it has an overload that takes a ReadOnlyMemory<byte>. This will be more efficient than wrapping the memory in a Stream.

I'd like to tackle this and some of the other performance related comments when we have updated to v23

CurtHagenlocher · 2026-09-02T03:46:39Z

+                return null;
+
+            _currentStream = nextChunk.Stream;
+            _currentReader = new Ipc.ArrowStreamReader(_currentStream);


If you know this is going to be a MemoryStream (or even if you suspect it could be) then it might be worth extracting the underlying buffer and converting it to a ReadOnlyMemory of the appropriate length and passing that to the constructor of ArrowStreamReader. (Or at least it's worth benchmarking -- I don't remember exactly what the deserialization tries to do and it's possible that using a Stream as a source gives more but smaller allocations in a way that actually ends up better off by avoiding the LOH and/or freeing more memory sooner.)

noted, will bucket with 'I'd like to tackle this and some of the other performance related comments when we have updated to v23'

CurtHagenlocher · 2026-09-02T03:50:10Z

+                case TimestampLtzLogicalType:
+                case TimestampTzLogicalType:
+                {
+                    // TZ carries a per-row offset field (dropped — we store the UTC instant); NTZ


See other comment about the possibility of using the extension type.

noted, will bucket with 'I'd like to tackle this and some of the other performance related comments when we have updated to v23'

CurtHagenlocher · 2026-09-02T03:54:32Z

+    private const long NanosecondsPerSecond = 1_000_000_000L;
+
+    private readonly Ipc.IArrowArrayStream _inner;
+    private readonly List<ColumnTransform> _transforms;


I think there are probably some optimization opportunities in here. The C# builders aren't particularly efficient, and I think you could probably use the new Int128 type in the BCL instead of decimal to load Decimal128Array more efficiently. We really need to get a bunch of this kind of functionality into the base C# Arrow libraries :/.

…e explicit

…urns

… to update submodule

…for the cleanup path

ndglover requested review from lidavidm and zeroshade as code owners July 14, 2026 14:27

ndglover force-pushed the initial branch 2 times, most recently from 6a7ba51 to aaba4ec Compare July 21, 2026 14:21

lidavidm reviewed Jul 29, 2026

View reviewed changes

ndglover added 6 commits July 31, 2026 16:35

fix(csharp): dispose previously bound parameters on re-bind

9be9c94

fix(csharp): reject unparseable connection parameters instead of igno…

6183015

…ring them

chore(csharp): add missing license headers to native driver files

2d0cfbe

chore(csharp): add .editorconfig and format native driver

153b6da

chore(csharp): fix linting

a65e099

ndglover force-pushed the initial branch from 03b2146 to a65e099 Compare July 31, 2026 15:38

chore(csharp): correct license headers on original native driver files

bfeac75

CurtHagenlocher requested a lite review from Copilot September 1, 2026 15:09

Copilot started reviewing on behalf of CurtHagenlocher September 1, 2026 15:09 View session

Copilot AI reviewed Sep 1, 2026

View reviewed changes

CurtHagenlocher approved these changes Sep 2, 2026

View reviewed changes

ndglover added 9 commits September 2, 2026 17:22

fix(csharp): improve and validate account and endpoint parameters

45678e5

refactor(csharp): name the credential fingerprint delimiter to be mor…

e4ad83b

…e explicit

chore(csharp): remove whitespace

10fee67

fix(csharp): align described column types with the data Snowflake ret…

c5bb365

…urns

docs(csharp): correct why TIMESTAMP_TZ drops its per-row offset, need…

7cb7a8f

… to update submodule

feat(csharp): assign AdbcStatusCode to driver exceptions

295f5e1

refactor(csharp): drop the pool's idle lock - protection was minimal …

87e9c13

…for the cleanup path

feat(csharp): expose connection parameter names as public constants

c3ca194

		<PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="9.0.0" />
		<PackageReference Include="Microsoft.Extensions.TimeProvider.Testing" Version="9.0.0" />

		@@ -0,0 +1,64 @@
		/*
		* Copyright (c) 2025 ADBC Drivers Contributors

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ndglover commented Jul 31, 2026

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