FIX: FetchMany(number of rows) ignores batch size with LOB columns

[David Levy (dlevy-msft-sql)]

Work Item / Issue Reference

GitHub Issue: #345

---

Summary

Fixes FetchMany(number of rows) ignores batch size when table contains an LOB

[Copilot]

Pull request overview

This PR fixes a bug where FetchMany(number of rows) ignores the batch size parameter when tables contain LOB (Large Object) columns such as NVARCHAR(MAX). The fix ensures that when LOB columns are detected, the row-by-row fetch path properly limits the number of rows fetched to the specified batch size.

Key Changes:

• Modified the LOB fetch loop in C++ to respect the fetchSize parameter by adding a loop condition check
• Added a new lob_wvarchar_column (NVARCHAR(MAX)) column to the test table schema to enable LOB testing
• Created dedicated test functions to validate fetch operations (fetchone, fetchmany, fetchall) with LOB columns present

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 9 comments.

File	Description
mssql_python/pybind/ddbc_bindings.cpp	Fixed FetchMany_wrap to break the LOB fetch loop when numRowsFetched reaches fetchSize, preventing infinite fetching
tests/test_004_cursor.py	Added lob_wvarchar_column to test table, updated test data, and added new test functions to validate fetch behavior with LOB columns

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Sumit Sarabhai (sumitmsft)]

Left a few comments to be addressed.

gargsaumya please review this PR.

[David Levy (dlevy-msft-sql)]

Sumit Sarabhai (@sumitmsft) this one is ready for review again. The code coverage report issues seem to be breaking the workflow.

[github-actions]

📊 Code Coverage Report

🔥 Diff Coverage 100%

🎯 Overall Coverage 76%

📈 Total Lines Covered: 5439 out of 7114 📁 Project: mssql-python

---

Diff Coverage

Diff: main...HEAD, staged and unstaged changes

• mssql_python/pybind/ddbc_bindings.cpp (100%)

Summary

• Total: 3 lines
• Missing: 0 lines
• Coverage: 100%

---

📋 Files Needing Attention

📉 Files with overall lowest coverage (click to expand)

mssql_python.pybind.logger_bridge.hpp: 58.8%
mssql_python.pybind.logger_bridge.cpp: 59.2%
mssql_python.row.py: 66.2%
mssql_python.helpers.py: 67.5%
mssql_python.pybind.ddbc_bindings.cpp: 69.4%
mssql_python.pybind.ddbc_bindings.h: 71.7%
mssql_python.pybind.connection.connection.cpp: 73.6%
mssql_python.ddbc_bindings.py: 79.6%
mssql_python.pybind.connection.connection_pool.cpp: 79.6%
mssql_python.connection.py: 83.9%

---

🔗 Quick Links

⚙️ Build Summary	📋 Coverage Details
View Azure DevOps Build	Browse Full Coverage Report

[gargsaumya]

LGTM!
This PR will also correctly resolve #390, validated this locally with VARCHAR(MAX) columns. Approving.

Closing this review - the fix has been validated.