fetch_df_batches() segfaults with fetch_decimals=True and repeated NUMBER values across batches

[szymongalecki]

1. What versions are you using?

oracle database version: 19.31.0.0.0
thin mode: True
platform.platform: Linux-6.18.33.2-microsoft-standard-WSL2-x86_64-with-glibc2.39
sys.maxsize > 2**32: True
platform.python_version: 3.12.0
python-oracledb: 26.0.0

2. Is it an error or a hang or a crash?
   Crash - Fatal Python error: Segmentation fault, exit code 139

3. What error(s) or behavior you are seeing?
   Method Connection.fetch_df_batches() terminates the Python process with segmentation fault when: its parameter fetch_decimals=True AND a NUMBER value is repeated AND fetching continues into a second batch.

4. Does your application call init_oracle_client()?
   No.

5. Include a runnable Python script that shows the problem.

import faulthandler
import oracledb

faulthandler.enable()

query = """
select cast(0 as number(10, 0)) as n
from dual
connect by level <= 4
"""

with oracledb.connect(
    user="<user>",
    password="<password>",
    dsn="<dsn>",
) as connection:
    for index, batch in enumerate(
        connection.fetch_df_batches(
            statement=query,
            size=2,
            fetch_decimals=True,
        )
    ):
        print(index, batch.num_rows())

Expected output - both batches are fetched:

0 2
1 2

Actual output - only the first batch is returned:

0 2
Fatal Python error: Segmentation fault

Current thread 0x00007a1998319740 (most recent call first):
  File "/<user_path>/.venv/lib/python3.12/site-packages/oracledb/connection.py", line 1686 in fetch_df_batches
  File "/<user_path>/segfault.py", line 28 in <module>

Extension modules: oracledb.arrow_impl, oracledb.base_impl, oracledb.thick_impl, _cffi_backend, oracledb.thin_impl (total: 5)

[anthony-tuininga]

I am unable to replicate this issue. I tried this on native Linux, not WSL2, though. It might be platform specific. Any chance you can get the full traceback? Maybe that will be enough to figure out the source of the issue?

[szymongalecki]

To exclude that this is platform specific, I ran it on Windows 11.

oracle database version: 19.31.0.0.0
thin mode: True                                                                          
platform.platform: Windows-11-10.0.26100-SP0
sys.maxsize > 2**32: True                                                                                      
platform.python_version: 3.13.14                                                           
python-oracledb: 26.0.0                                                                     

0 2                   
Windows fatal exception: access violation

Current thread 0x00008818 (most recent call first):
  File "C:\<user_path>\segfault\venv\Lib\site-packages\oracledb\connection.py", line 1686 in fetch_df_batches
  File "C:\<user_path>\segfault\segfault.py", line 32 in <module>

I also ran it again with Linux but using different version of glibc (previously 2.39), and I hope this backtrace is what you wanted :)

app-1  | oracle database version: 19.31.0.0.0
app-1  | thin mode: True
app-1  | platform.platform: Linux-6.18.33.2-microsoft-standard-WSL2-x86_64-with-glibc2.28
app-1  | sys.maxsize > 2**32: True
app-1  | platform.python_version: 3.12.13
app-1  | python-oracledb: 26.0.0
app-1  |
app-1  | 0 2
app-1  | Fatal Python error: Segmentation fault
app-1  |
app-1  | Current thread 0x00007e9d348f5740 (most recent call first):
app-1  |   File "/opt/venv/lib/python3.12/site-packages/oracledb/connection.py", line 1686 in fetch_df_batches
app-1  |   File "/app/segfault.py", line 35 in <module>
app-1  |
app-1  | Extension modules: oracledb.arrow_impl, oracledb.base_impl, oracledb.thick_impl, _cffi_backend, oracledb.thin_impl (total: 5)
app-1  |
app-1  | Native backtrace, libc and oracledb frames only (most recent call first):
app-1  |   __memcpy_avx512_unaligned_erms
app-1  |   __pyx_f_8oracledb_10arrow_impl_14ArrowArrayImpl_append_last_value
app-1  |   __pyx_f_8oracledb_9thin_impl_15MessageWithData__process_row_data
app-1  |   __pyx_f_8oracledb_9thin_impl_15MessageWithData__process_message
app-1  |   __pyx_f_8oracledb_9thin_impl_7Message_process
app-1  |   __pyx_f_8oracledb_9thin_impl_8Protocol__process_message
app-1  |   __pyx_f_8oracledb_9thin_impl_8Protocol__process_round_trip
app-1  |   __pyx_f_8oracledb_9thin_impl_8Protocol__process_single_message
app-1  |   __pyx_f_8oracledb_9thin_impl_12ThinConnImpl__process_sync_operation_sub_op
app-1  |   __pyx_pf_8oracledb_9base_impl_12BaseConnImpl_92process_sync_operation
app-1  |     inlined by __pyx_pw_8oracledb_9base_impl_12BaseConnImpl_93process_sync_operation
app-1 exited with code 139