FEAT: Adding cursor.lastrowid attribute

[jahnvi480]

Work Item / Issue Reference

AB#34897

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Summary

This pull request adds support for the lastrowid attribute to the Cursor class, allowing users to retrieve the row ID of the last inserted row after single-row INSERT operations. The implementation ensures compliance with DB-API semantics and includes comprehensive tests to verify correct behavior in various scenarios.

Enhancements to Cursor functionality:

• Added a read-only lastrowid property to the Cursor class, tracking the row ID of the last modified row, and ensuring it is set only for single-row INSERT operations.
• Updated the execute method to set lastrowid using the result of SELECT @@IDENTITY after a successful single-row INSERT, and reset it to None at the start of each execution.
• Ensured that lastrowid is reset to None at the start of executemany, as semantics are undefined for multi-row operations.

Testing improvements:

• Added a comprehensive suite of tests for lastrowid, covering single and multiple inserts, executemany, non-INSERT operations, tables without identity columns, and enforcement of the read-only property.

[Copilot]

Pull Request Overview

This pull request implements the lastrowid attribute for the Cursor class, providing DB-API 2.0 compliance by allowing retrieval of the last inserted row's identity value. The implementation ensures lastrowid is only set for single-row INSERT operations and remains None for other operations or batch executions.

• Added a read-only lastrowid property that queries @@IDENTITY after successful single-row INSERTs
• Reset lastrowid to None for non-INSERT operations, multi-row INSERTs, and executemany calls
• Comprehensive test coverage for various scenarios including identity and non-identity tables

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
mssql_python/cursor.py	Implements lastrowid property with logic to detect single-row INSERTs and query @@IDENTITY
tests/test_004_cursor.py	Adds extensive test cases covering all lastrowid scenarios and edge cases

Comments suppressed due to low confidence (1)

tests/test_004_cursor.py:1359

• This test doesn't verify that the INSERT actually succeeded and affected multiple rows. Consider adding an assertion to check cursor.rowcount == 3 to ensure the test is validating the correct scenario.

        cursor.execute("INSERT INTO #test_lastrowid (name) VALUES ('test1'), ('test2'), ('test3')")

[bewithgaurav]

There are a few limitations on ODBC w.r.t implementation and usage of this attribute, added comments in detail. I believe we can discuss this in detail and park it for now.
Additionally, this is an optional DBAPI extension - https://peps.python.org/pep-0249/#lastrowid and is not implemented by pyodbc due to the above mentioned limitations. Lets discuss this in next meeting.

[sumitmsft]

Left a comment for @@IDENTITY VS SCOPE_IDENTITY() .. Let's discuss where the challenge is @jahnvi480 @@IDENTITY can return unexpected results if there are triggers on the table that perform additional inserts.

[github-actions]

📊 Code Coverage Report

🔥 Diff Coverage 82%

🎯 Overall Coverage 74%

📈 Total Lines Covered: 4204 out of 5624 📁 Project: mssql-python

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Diff Coverage

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

• mssql_python/cursor.py (82.4%): Missing lines 1073,1075-1076

Summary

• Total: 17 lines
• Missing: 3 lines
• Coverage: 82%

mssql_python/cursor.py

Lines 1069-1080

  1069                 if (fetch_ret == ddbc_sql_const.SQL_SUCCESS.value and 
  1070                     row_data and row_data[0] is not None):
  1071                     self._lastrowid = int(row_data[0])
  1072 
! 1073         except Exception:
  1074             # If we can't get the identity, leave lastrowid as None
! 1075             self._lastrowid = None
! 1076             log('debug', "Could not retrieve lastrowid: %s", e)
  1077 
  1078         # Return self for method chaining
  1079         return self

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📋 Files Needing Attention

📉 Files with overall lowest coverage (click to expand)

mssql_python.pybind.connection.connection.cpp: 68.3%
mssql_python.ddbc_bindings.py: 68.5%
mssql_python.pybind.ddbc_bindings.cpp: 69.7%
mssql_python.pybind.connection.connection_pool.cpp: 78.9%
mssql_python.cursor.py: 79.7%
mssql_python.connection.py: 81.7%
mssql_python.helpers.py: 84.7%
mssql_python.auth.py: 85.3%
mssql_python.type.py: 86.8%
mssql_python.pooling.py: 87.5%

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