Per the ClickHouse url() table function reference, headers must be the 4th positional argument inside the function call, with structure as the 3rd positional argument (defaulting to 'auto' when not provided — chdb rejects '' with Code: 36 Table structure is empty).

Changes

• Move headers into sql_params before f"url(...)" construction so they end up inside url() as the 4th positional arg
• Pad missing format/structure positional slots to 'auto' via sql_params.extend(["'auto'"] * (3 - len(sql_params)))
• Convert "Key: Value" strings to 'Key'='Value' pairs per ClickHouse's headers() function syntax
• Support dict input directly (headers={"Authorization": "Bearer xyz"})
• Existing format/structure handling block is preserved unchanged

Tests

New file datastore/tests/test_url_table_function_headers.py with class TestUrlTableFunctionHeaders (8 methods, matching the existing test_table_functions.py class-based convention):

• test_to_sql_no_headers_unchanged — regression guard for no-headers case
• test_to_sql_with_headers_inside_url_call — confirms headers emit inside url()
• test_to_sql_headers_pad_structure_auto — structure auto-padded when format provided
• test_to_sql_headers_pad_format_and_structure_auto — both auto-padded when neither provided
• test_to_sql_headers_dict_input — dict input support
• test_to_sql_headers_multiple_entries — multiple headers
• test_to_sql_headers_missing_url_raises — confirms the new headers code path doesn't suppress the existing url-required validation
• test_to_sql_headers_executes_via_chdb — end-to-end runtime check: the generated SQL parses and executes via chdb.query() against https://httpbin.org/ip (skips gracefully if chdb or network unavailable)

Updated existing test_url_with_headers_list and test_url_with_headers_string in test_table_functions.py — they were asserting the broken output, now assert the correct fixed shape.

Verification

• All 10,688 existing datastore/tests/ tests PASS (no regressions; 9 skipped, 85 xfailed, 4 xpassed all unchanged from baseline)
• 8 new tests PASS, including the runtime SQL execution check
• Empirically verified: fixed SQL executes cleanly against https://httpbin.org/ip with chdb 4.1.6 (Python 3.13, macOS arm64) — returns expected JSON, no parse error

Issue

#564