FIX: Improvement to parameter type inference and handling

[gargsaumya]

Work Item / Issue Reference

AB#38383

GitHub Issue: #<ISSUE_NUMBER>

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Summary

This pull request refactors the logic for inferring SQL types from Python parameters in the mssql_python/cursor.py module, especially for batch operations using executemany. The main improvements are more accurate type detection for integer columns by considering the minimum and maximum values in the data, and a cleaner separation of concerns in the codebase.

Improvements to type inference and parameter handling:

• Refactored the type mapping logic in _map_sql_type to use min_val and max_val for integer columns, allowing for more accurate type selection based on the actual range of values in the data.
• Updated _create_parameter_types_list to accept and forward min_val and max_val, supporting the improved type inference for batch operations.
• Replaced the static method _select_best_sample_value with a new _compute_column_type method, which determines a representative sample value and computes min/max for integer columns, enhancing how types are inferred for each parameter column in executemany. [1] [2]
• Modified the executemany method to use _compute_column_type for each parameter column, passing the computed min/max values to _create_parameter_types_list for better type assignment.

Code cleanup:

• Removed the now-unnecessary _select_best_sample_value static method, consolidating logic and reducing code duplication.

[Copilot]

Pull Request Overview

This pull request improves parameter type inference and handling in the executemany method by replacing the static _select_best_sample_value method with a more comprehensive _compute_column_type method. The changes enhance accuracy for batch operations with varied data types, particularly for integer range detection and Data At Execution (DAE) handling.

• Replaced static sample value selection with comprehensive column analysis that computes representative values, DAE flags, and min/max ranges
• Enhanced integer type mapping to use min/max values for more accurate SQL type selection
• Updated parameter creation pipeline to pass computed range information through the type mapping process

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[sumitmsft]

Got this from Copilot:

Missing test coverage for:

Batch decimal precision/scale aggregation
Large string threshold (NVARCHAR vs NVARCHAR(MAX)) including astral (UTF‑16 surrogate pair) edge cases
executemany sampling when a later row crosses the 4000 UTF‑16 unit boundary
Mixed Unicode/non-Unicode large strings (type chosen, DAE flag)
All‑NULL column inference (no crash, consistent default type)
Mixed bool and int values (BIT vs widen to INT)
Mixed numeric & string column fallback (string coercion, no silent truncation)
Large negative integers (e.g. −2^63+1) and 64‑bit boundary extremes (±2^63−1, ±2^31, etc.)
Mixed bool + very large int (widening logic)
Astral-heavy string where len(s) < 4000 but UTF‑16 units > 4000 (correct MAX path)
Large binary (>8000) bytes vs bytearray parity (same SQL type + isDAE)
Binary exactly at 8000 and just over (boundary behavior)
All parameters None in a column (executemany robustness)

Some tests may not be worth, so take your call and select the relevant ones.

[bewithgaurav]

need to merge to latest main