PERF: Reduce Python Row indexing overhead

[Jahnvi Thakkar (jahnvi480)]

Work Item / Issue Reference

AB#48366

Summary

Add a two-line fast path in Row.__getitem__ for indexes whose exact type is int, returning the stored value directly. Keep the existing fallback order unchanged for booleans, integer subclasses, slices and column-name access.

Only mssql_python/row.py changes. No public API, native code, tests, build configuration or CI changes are included.

[github-actions]

PR Performance Report

✅ No regression detected

No consistent slowdowns detected across all 2 environments.

0 IMPROVEMENTS 0 SLOWDOWNS 2/2 ENVIRONMENTS

Coverage: 2 of 2 environments completed. Advisory result; does not block merging.

Performance diagnostics

Phase times are inclusive diagnostics and must not be added together. They identify where measured time changed, not why it changed.

No affected phases or call-count changes were recorded.

All database tasks and timings

Unix / SQL Server 2022

Database task	Before	After	Paired change	Result
Connection opening	10.390 ms	10.356 ms	-0.3%	no signal
SELECT queries	1.058 ms	1.237 ms	+16.6%	no signal
Row insertion	34.410 ms	35.246 ms	+1.8%	no signal
Executemany inserts	154.786 ms	156.690 ms	+1.4%	no signal
Fetch-all queries	120.472 ms	121.386 ms	+0.8%	no signal
Row-by-row fetching	14.473 ms	14.337 ms	-0.9%	no signal
Batched row fetching	120.258 ms	118.015 ms	-1.5%	no signal
Transaction commit and rollback	113.345 ms	113.171 ms	-2.3%	no signal
Arrow row fetching	94.995 ms	95.563 ms	-0.2%	no signal
100,000-row insertion	442.666 ms	447.702 ms	+1.1%	no signal
Row fetching in batches of 100	121.265 ms	121.803 ms	+0.8%	no signal
Row fetching in batches of 10,000	125.235 ms	138.390 ms	+10.5%	no signal
Repeated positional queries	33.676 ms	34.124 ms	-0.5%	no signal
Repeated named-parameter queries	36.655 ms	35.539 ms	-3.0%	no signal
Legacy 100,000-row insertion	349.230 ms	353.975 ms	+1.6%	no signal
Insertion with explicit input sizes	483.134 ms	482.317 ms	+0.5%	no signal
Joined aggregation queries	177.425 ms	177.651 ms	+0.1%	no signal
Large joined-result fetching	180.416 ms	180.188 ms	+0.2%	no signal
1.2-million-row fetching	3470.772 ms	3527.123 ms	+1.2%	no signal
Common table expression queries	5.364 ms	5.438 ms	+1.0%	no signal
256 KiB VARCHAR(MAX) / fetchall()	1.325 ms	1.220 ms	-2.9%	no signal

Unix / SQL Server 2025

Database task	Before	After	Paired change	Result
Connection opening	97.901 ms	97.747 ms	+0.3%	no signal
SELECT queries	1.091 ms	1.083 ms	+0.3%	no signal
Row insertion	34.731 ms	34.612 ms	-0.1%	no signal
Executemany inserts	150.908 ms	151.824 ms	+0.1%	no signal
Fetch-all queries	124.663 ms	123.074 ms	-1.0%	no signal
Row-by-row fetching	15.224 ms	14.454 ms	-4.2%	no signal
Batched row fetching	121.410 ms	119.374 ms	-1.4%	no signal
Transaction commit and rollback	115.368 ms	115.483 ms	+0.1%	no signal
Arrow row fetching	95.038 ms	95.323 ms	+0.5%	no signal
100,000-row insertion	479.485 ms	448.188 ms	-5.1%	no signal
Row fetching in batches of 100	124.230 ms	123.274 ms	-0.5%	no signal
Row fetching in batches of 10,000	130.075 ms	129.763 ms	-0.3%	no signal
Repeated positional queries	34.012 ms	33.517 ms	-1.5%	no signal
Repeated named-parameter queries	36.468 ms	36.141 ms	+0.4%	no signal
Legacy 100,000-row insertion	355.478 ms	359.343 ms	-0.6%	no signal
Insertion with explicit input sizes	487.333 ms	492.532 ms	+1.1%	no signal
Joined aggregation queries	161.264 ms	161.150 ms	+0.2%	no signal
Large joined-result fetching	189.173 ms	186.827 ms	-1.2%	no signal
1.2-million-row fetching	3502.387 ms	3479.956 ms	-0.7%	no signal
Common table expression queries	5.185 ms	5.270 ms	+1.1%	no signal
256 KiB VARCHAR(MAX) / fetchall()	1.539 ms	1.555 ms	-0.3%	no signal

Build and measurement details

ADO build 178639

PR head: 60519f5825091f97a85d26c6edfd14391c1625df
Base: d849a09119c831d945521d5333cfb9bdb6e0561d
Measured merge: ff086676e1ff2bccf41bf4383c9555d5013189da

• Unix / SQL Server 2022: Python 3.12.3, x86_64, SQL 16.0.4295.3; 5 paired comparisons and 1 warmup.
• Unix / SQL Server 2025: Python 3.12.3, x86_64, SQL 17.0.5005.3; 5 paired comparisons and 1 warmup.

A consistent change requires more than 20% median paired movement, at least 1 ms between the median runtimes, and at least 80% of pairs exceeding the relative threshold in the same direction. A slowdown without enough pair agreement is reported as inconsistent.

The displayed change is the median of paired before-and-after ratios. It is not recalculated from the two displayed median runtimes.

Both revisions use profiling-enabled builds on the same agent and database, with alternating order and discarded warmups. Results are diagnostic and do not represent production-wheel latency.

Raw samples and logs are attached to the ADO run as profiler-* artifacts.

[Copilot]

Copilot review overview

🔵 Needs a closer look

Add regression coverage for boolean and integer-subclass indexing and provide current-main performance validation.

Review effort: Lite
Findings: None

What changed in this PR

Adds an exact-int fast path to Row.__getitem__ to reduce positional indexing overhead while preserving fallback behavior.

Changes:

• Directly returns stored values for exact integer indexes.
• Retains existing handling for booleans, integer subclasses, slices, and column names.
• Adds no API, native, build, or CI changes.

File	Description
mssql_python/​row.py	Adds the positional integer indexing fast path.

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[github-actions]

📊 Code Coverage Report

🔥 Diff Coverage 100%

🎯 Overall Coverage 84%

📈 Total Lines Covered: 9402 out of 11085 📁 Project: mssql-python

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Diff Coverage

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

• mssql_python/row.py (100%)

Summary

• Total: 2 lines
• Missing: 0 lines
• Coverage: 100%

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📋 Files Needing Attention

📉 Files with overall lowest coverage (click to expand)

mssql_python.pybind.performance_counter.hpp: 0.7%
mssql_python.pybind.logger_bridge.cpp: 57.9%
mssql_python.pybind.ddbc_bindings.h: 62.6%
mssql_python.pybind.logger_bridge.hpp: 70.8%
mssql_python.pybind.ddbc_bindings.cpp: 79.3%
mssql_python.pybind.connection.connection_pool.cpp: 82.3%
mssql_python.pybind.connection.connection.cpp: 83.1%
mssql_python.logging.py: 86.2%
mssql_python.pooling.py: 90.1%
mssql_python.pybind.fetch_temporal.hpp: 92.1%

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🔗 Quick Links

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

[Copilot]

Copilot review overview

🟢 Approval recommended

The remaining test-coverage comment is a non-blocking nit.

Review effort: Lite
Findings: 1

Open (1)

• Add regression tests for Row indexing dispatch and fallback types · New