Python Oracledb - Segmentation Fault Error

Question

When I use oracledb Python module in Thick mode, I get a Segmentation fault error on a huge database request with Oracle v11.2 client.

Code:

# main.py
import oracledb

oracledb.init_oracle(lib_dir='path/to/lib', config_dir='path/to/config')
connection = oracledb.connect(user='user', password='pwd', dsn=cs, sid=sid, encoding='utf-8')
cursor = connection.cursor()
cur.arraysize = 100

results = cur.execute('SELECT * FROM MY_TABLE')

Error:

python main.py
Segmentation fault

What is the problem with this request?

In my case, MYTABLE is Materialized View with a lot of columns and rows. I get the segfault after the line "results = cur.execute('SELECT * FROM MY_TABLE')". I also have the error when I use SQL Alchemy + Pandas + dbOracle after "pandas.read_sql()" (pandas v1.1.5) even if I use chunks of size 1. Setting "ORA_OCI_NO_OPTIMIZED_FETCH=1" fixed the issue with larger chunksize. — Adrien Arcuri, Commented Mar 27, 2023 at 21:51
Ok! You can also try thin mode (by commenting out the call to init_oracle_client() as it doesn't have that particular bug. It doesn't have all of the same features but it does have all of the commonly used ones! — Anthony Tuininga, Commented Mar 28, 2023 at 14:44
Oracledb client tell me that Thin mode is not compatible with Oracle DB v11.2.0, that's why I can only use Thick mode in my case. — Adrien Arcuri, Commented Mar 28, 2023 at 20:06

Adrien Arcuri · Accepted Answer · 2023-03-27 16:54:51Z

0

It may be a bug in your Oracle Client version at the C level.

To correct it, try to set the ORA_OCI_NO_OPTIMIZED_FETCH environnement variable to 1 in order to disable fetch Oracle compression - which can make your code failed- before running your Python code:

export ORA_OCI_NO_OPTIMIZED_FETCH=1
python main.py

You can also try to update your Oracle client because this bug is probably fix in a more recent version or patch.

answered Mar 27, 2023 at 16:54

Adrien Arcuri

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1

Yes the particular problem that ORA_OCI_NO_OPTIMIZED_FETCH resolves was fixed in 21c Oracle client libraries, and I think backported to a later 19c release (but I don't have that info with me).
– Christopher Jones
Commented Mar 28, 2023 at 21:24

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wa-Nadoo · Accepted Answer · 2025-03-28 20:53:00Z

0

This issue was recently fixed in https://github.com/oracle/odpi/commit/3a578197cae567028bfe9d39e7e05bfc5869c650 and will be released as part of python-oracledb 3.1.0

answered Mar 28 at 20:53

wa-Nadoo

1

2

The fix you reference may be a different issue. It stops a crash when client libraries can't be loaded and gives a proper error instead. The user would still need to fix their environment and set lib_dir to a valid library path, or use LD_LIBRARY_PATH etc. Note: that on Linux, you should NOT pass lib_dir to init_oracle_client() - it doesn't do what you want, and can lead to other clashes. Only pass it on Windows and macOS. RTM.
– Christopher Jones
Commented Mar 28 at 21:42

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