SNOW-969175: Decimals with precision greater than 18 are returned as object type when using the to_pandas method

Please answer these questions before submitting your issue. Thanks!

1. What version of Python are you using?

3.8.5

2. What operating system and processor architecture are you using?

Windows-10-10.0.19041-SP0

3. What are the component versions in the environment (pip freeze)?

altair==4.2.2
asn1crypto==1.5.1
attrs==23.1.0
azure-core==1.29.3
azure-storage-blob==12.17.0
backports.zoneinfo==0.2.1
blinker==1.6.2
cachetools==5.3.1
certifi==2023.7.22
cffi==1.15.1
charset-normalizer==3.2.0
click==8.1.7
cloudpickle==2.0.0
colorama==0.4.6
coverage==7.3.1
cryptography==41.0.3
dill==0.3.7
entrypoints==0.4
exceptiongroup==1.1.3
filelock==3.12.3
gitdb==4.0.10
GitPython==3.1.35
idna==3.4
importlib-metadata==6.8.0
importlib-resources==6.0.1
iniconfig==2.0.0
isodate==0.6.1
jaraco.classes==3.3.0
Jinja2==3.1.2
jsonschema==4.19.0
jsonschema-specifications==2023.7.1
keyring==24.2.0
markdown-it-py==3.0.0
MarkupSafe==2.1.3
mdurl==0.1.2
more-itertools==10.1.0
numpy==1.24.4
oscrypto==1.3.0
packaging==23.1
pandas==2.0.3
Pillow==9.5.0
pkgutil_resolve_name==1.3.10
platformdirs==3.8.1
pluggy==1.3.0
protobuf==3.20.3
pyarrow==10.0.1
pycparser==2.21
pycryptodomex==3.18.0
pydeck==0.8.0
Pygments==2.16.1
PyJWT==2.8.0
Pympler==1.0.1
pyOpenSSL==23.2.0
pytest==7.4.2
pytest-azurepipelines==1.0.4
pytest-cov==4.1.0
pytest-nunit==1.0.3
python-dateutil==2.8.2
pytz==2023.3.post1
pytz-deprecation-shim==0.1.0.post0
pywin32-ctypes==0.2.2
snowflake-snowpark-python==1.8.0
sortedcontainers==2.4.0
streamlit==1.22.0
tenacity==8.2.3
toml==0.10.2
tomli==2.0.1
tomlkit==0.12.1
toolz==0.12.0
tornado==6.3.3
typing_extensions==4.7.1
tzdata==2023.3
tzlocal==4.3.1
urllib3==1.26.16
validators==0.22.0
watchdog==3.0.0
zipp==3.16.2

4. What did you do?
   you can execute the following script to see that converting a decimal column from a snowpark dataframe to pandas dataframe can have different pandas data type, depending on the precision.

from snowflake.snowpark.types import DecimalType
from snowflake.snowpark.functions import col,cast


session = #create your snowpark session here

# returns data as float64 (expected)
snowpark_df = session.create_dataframe([1.5, 234.5], schema=["a"]).with_column("a", cast(col("a"), DecimalType(18, 6)))
print(snowpark_df.to_pandas().dtypes)

# returns as object (unexpected)
snowpark_df = session.create_dataframe([1.5, 234.5], schema=["a"]).with_column("a", cast(col("a"), DecimalType(19, 6)))
print(snowpark_df.to_pandas().dtypes)

5. What did you expect to see?
   I would expect for both to be returned as float64 in the pandas dataframe. If there is not possible because of a limitation with float64, then it would be helpful to have some type of option in the to_pandas() method, to return decimal types as float64 when the precision is greater than 18.

Start by running the supplied Snowpark script and comparing the pandas dtypes for DecimalType(18, 6) and DecimalType(19, 6). Trace the to_pandas conversion path that handles decimal precision; done means the behavior for precision greater than 18 is consistent with the documented expectation or has a clearly defined conversion option.