[polyglotAI-bot]

Summary

Fixes #683.

ChangeDatabase stores the database on the connection only. ClickHouseClient.CreateUriBuilder uses queryOverride?.Database ?? Settings.Database. ClickHouseCommand passes connection.Database, but two other paths that go through the connection did not:

• ClickHouseConnection.PostStreamAsync (both overloads) passed options with only QueryId, or null when no query id was given.
• ClickHouseBulkCopy.WriteToServerAsync built its InsertOptions without Database.

Both paths therefore ran in the configured database. An unqualified table name resolved in the wrong database: the call failed with UNKNOWN_TABLE, or, if a table with the same name existed there, the rows went into it with no error.

Changes

• ClickHouseConnection.PostStreamAsync: always build QueryOptions with Database = Database (plus QueryId when given). All other options stay null, so the request is the same as before apart from the database.
• ClickHouseBulkCopy.WriteToServerAsync: set Database = connection.Database on the InsertOptions. It is read at write time, so a ChangeDatabase after the bulk copy is constructed also applies. InsertOptions.Database drives both the schema probe and the INSERT.
• Changelog fragment changelog.d/683-change-database-post-stream-bulk-copy.fixes.md.

Without ChangeDatabase, Database returns Settings.Database, so those requests do not change. ClickHouseBulkCopy(string connectionString) owns its connection, so it is not affected.

Tests

• ConnectionTests.PostStreamAsync_AfterChangeDatabase_RunsInSelectedDatabase: both overloads, with and without a query id (the two branches of the old options helper). Runs SELECT currentDatabase() after ChangeDatabase("system"). On main all 4 cases return default.
• BulkCopyTests.WriteToServerAsync_AfterChangeDatabase_InsertsIntoSelectedDatabase: RowBinary and RowBinaryWithDefaults. The table exists only in test_secondary and the bulk copy gets the bare name. On main both cases fail with UNKNOWN_TABLE from the schema probe.

The new tests fail on main and pass with the fix. Full ClickHouse.Driver.Tests run on net10.0 against ClickHouse 26.9: 14825 passed, 0 failed, no existing tests changed.

Related, not changed here: Clone() also drops the database chosen with ChangeDatabase (#682).

Checklist

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG

🤖 Generated with Claude Code

[Copilot]

🟡 Changes recommended

The public behavior correction still needs the required update to the HTTP user guide.

1 open finding

• Document selected database behavior in the ADO.NET section · New

What changed in this PR

Fixes #683 in the HTTP client so stream requests and bulk copies respect the database selected by ChangeDatabase.

Changes:

• Pass the connection’s selected database through query and insert options.
• Add regression tests for both stream overloads and binary insert formats.
• Add a changelog fragment.

File	Description
ClickHouse.Driver/​Copy/​ClickHouseBulkCopy.cs	Selects the database at write time.
ClickHouse.Driver/​ADO/​ClickHouseConnection.cs	Includes the selected database in stream request options.
ClickHouse.Driver.Tests/​BulkCopy/​BulkCopyTests.cs	Tests database selection for both binary formats.
ClickHouse.Driver.Tests/​ADO/​ConnectionTests.cs	Tests both stream overloads with and without query IDs.
changelog.d/​683-change-database-post-stream-bulk-copy.fixes.md	Records the database-routing correction.

🧠 Review effort: Balanced

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