Make chdb an optional dependency for Windows compatibility

[joe-clickhouse]

Summary

• Moves chdb from a hard dependency to an optional extra via pip install mcp-clickhouse[chdb] fixing installation on Windows where chdb has no wheels
• Conditionally registers chdb tools only when the package is installed and initialization succeeds
• Clear error messages guiding users to install the extra if it's missing
• Updates README, fastmcp.json, and test commands to reflect the optional dependency

Closes #143

[Copilot]

Pull request overview

Makes chdb an optional extra so the package can install on Windows (where chdb wheels are unavailable), and gates chDB tool registration/runtime behavior based on whether the extra is installed and initialization succeeds.

Changes:

• Move chdb from a required dependency to an optional extra (mcp-clickhouse[chdb]) in packaging and lockfiles.
• Conditionally initialize/register chDB tools and improve error surfacing when chDB is enabled but unavailable.
• Update docs and tests to reflect the optional dependency and conditional behavior.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pyproject.toml	Moves chdb into an optional extra (chdb).
uv.lock	Updates locked metadata to mark chdb as an extra and advertise the extra.
mcp_clickhouse/mcp_server.py	Adds global chDB client/error state, conditional init/registration, and health reporting for chDB failures.
tests/test_optional_chdb.py	Adds unit tests for optional-dependency behavior and conditional tool registration.
tests/test_chdb_tool.py	Skips chDB tests when chdb isn’t installed.
fastmcp.json	Removes chdb from the default dependency list.
README.md	Documents the chdb extra and updates test command examples.

Comments suppressed due to low confidence (1)

tests/test_chdb_tool.py:17

• setUpClass calls create_chdb_client(), which raises ValueError unless CHDB_ENABLED=true. The test is only skipped based on whether chdb is installed, so running pytest tests/test_chdb_tool.py with the extra installed but without CHDB_ENABLED will fail. Consider setting CHDB_ENABLED=true in the test (or extending the skip condition to also require the env var).

@unittest.skipUnless(importlib.util.find_spec("chdb") is not None, "requires chdb extra")
class TestChDBTools(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        """Set up the environment before chDB tests."""
        cls.client = create_chdb_client()

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[busyerakli]

Don't know if I'm allowed to put approvals here, but LGTM

[Copilot]

Pull request overview

Copilot reviewed 6 out of 7 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

mcp_clickhouse/mcp_server.py:138

• In this branch, the code assumes both ClickHouse and chDB are disabled. However, it’s also reached when CHDB_ENABLED=true but _chdb_client is still None and _chdb_error_message is not set yet (e.g., chDB was enabled after module import, or init hasn’t been attempted). In that case the health check returns a misleading “both disabled” error. Consider handling chdb_config.enabled explicitly here (e.g., attempt _init_chdb_client() once, or return a distinct 503 like “chDB enabled but not initialized”).

            else:
                # Both ClickHouse and chDB are disabled - this is an error
                return PlainTextResponse(
                    "ERROR - Both ClickHouse and chDB are disabled. At least one must be enabled.",
                    status_code=503,

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