Insert Decimal with executemany throw an error

[Tweentyy]

Describe the bug

When attempting to add a Decimal to the database with an executemany, an error is returned.

Exception message: Exception: RuntimeError: Input string UTF-16 length exceeds allowed column size at parameter index 0. UTF-16 length: 20, Column size: 13
Stack trace:
[2025-10-02T10:57:39.569Z]   File "/Users/tweenty/Desktop/XXX/test.py", line 31, in insert_data
[2025-10-02T10:57:39.570Z]     cursor.executemany("INSERT INTO TestSQL (DecimalTest) VALUES (?)", data)
[2025-10-02T10:57:39.570Z]   File "/Users/tweenty/Desktop/XXX/.venv/lib/python3.12/site-packages/mssql_python/cursor.py", line 1682, in executemany
[2025-10-02T10:57:39.570Z]     ret = ddbc_bindings.SQLExecuteMany(
[2025-10-02T10:57:39.570Z] .

To reproduce

Create a table with Decimal:

CREATE TABLE TestSQL (
	DecimalTest DECIMAL(30, 20)
)

from decimal import Decimal

data = [(Decimal('35.1128407822'),), (Decimal('40000.56405640654065'),)]

cursor.execute("INSERT INTO TestSQL (DecimalTest) VALUES (?)", data[0]) # Works
cursor.executemany("INSERT INTO TestSQL (DecimalTest) VALUES (?)", data) # Doesn't work

Workaround found - Convert Decimal to str :

from decimal import Decimal

data = [(str(Decimal('35.1128407822')),), (str(Decimal('40000.56405640654065')),)]

cursor.execute("INSERT INTO TestSQL (DecimalTest) VALUES (?)", data[0]) # Works
cursor.executemany("INSERT INTO TestSQL (DecimalTest) VALUES (?)", data) # Works

Expected behavior

Insertion of lines into database.

Further technical details

Python version: 3.12.10
SQL Server version: SQL Server 2022
Operating system: macOS 26.0.1
mssql_python version: 0.13.0

[gargsaumya]

Thanks for trying out our driver and for sharing the details. We’ll take a look into this issue and update here once we have more information.
Please keep trying things out and raising issues. :)