ImportError: undefined symbol: PQencryptPasswordConn

[alexjpm]

Hi everyone,

I'm running PostgreSQL 9.6.13 on a raspberry pi 3B+. I'd been running psycopg2 version 2.8.3 with python 2.7.13 fine, but (finally!) have gotten round to upgrading to python 3.7.3. I created a new venv, pip installed psycopg2, and ran into this error:

ImportError: /usr/src/prt37/lib/python3.7/site-packages/psycopg2/_psycopg.cpython-37m-arm-linux-gnueabihf.so: undefined symbol: PQencryptPasswordConn

I've check pg_config and the libpq dependencies as suggested on the FAQ, and they're both using:
/usr/lib/arm-linux-gnueabihf/libpq.so.5

Has anyone got any ideas how to solve this and what is causing it? My python 2.7 venv is still running fine.

Thanks,

Alex

[dvarrazzo]

I'm pretty sure you have mismatch in the libpq header files and/or the libraries installed.

The PQencryptPasswordConn function was introduced in PG 10: psycopg uses it if it's find at compile time. However at runtime it tries to link with a pre-10 libpq and the function is not found.

Take a look at the build logs: you will likely see that PG_VERSION_NUM is greater than 10xxxx, which compiles in the PQencryptPasswordConn requirement. You can be sure of the libpq found at runtime e.g. running:

import ctypes
libpq = ctypes.cdll.LoadLibrary("libpq.so")
print(libpq.PQlibVersion())

which I bet is less that 10xxxx.

[alexjpm]

Thanks for the reply, I had a look and the result of that print statement is "90613". That all seems fine though as I want to use version 9.6 (as this is the latest supported version on the raspbian stretch OS).

Where can I find the psycopg2 build logs? There isn't anything in my "/usr/src/prt37/lib/python3.7/site-packages/psycopg2" that says what version of postgres tried to build with. postgres 9.6 is the only version on my pi, and pg_config and libpq are both looking for it.

[alexjpm]

Resolved by installing from source, 3.7 must've used the wheel.

git clone https://github.com/psycopg/psycopg2
cd psycopg2
`which python3.7` setup.py build
`which python3.7` setup.py install

[Harsh-Pandey]

@alexjpm i am still getting the same error after I did by method you mentioned. was there anything else as well I had to do after which python3.7 setup.py install

[alexjpm]

@alexjpm i am still getting the same error after I did by method you mentioned. was there anything else as well I had to do after which python3.7 setup.py install

Hi,
Are you installing directly to the system python or to a venv? If to a venv then double check the folder is owned by the right user. Other than that I didn't do anything else.

[nmvega]

I had this same issue and solved it by:

1. pip3 uninstall psycopg2
2. pip3 install psycopg2-binary
3. Uninstalling the (in my case Fedora RPM) packages for libpq and libpq-devel, which were no longer needed in my case (a lean docker container).

Things work well now.

[boooch]

I had this same issue and solved it by:

1. pip3 uninstall psycopg2
2. pip3 install psycopg2-binary
3. Uninstalling the (in my case Fedora RPM) packages for libpq and libpq-devel, which were no longer needed in my case (a lean docker container).

Things work well now.

Thank you, this helps me

[Anton-V-K]

The trick with uninstalling psycopg2 and installing psycopg2-binary didn't work out in my case, because the system (CentOS 7) was actually running PostgreSQL 9.5.24, while pg_config was reporting PostgreSQL 13.0 (the latter had been experimentally installed and hadn't been properly cleaned afterwards).
I couldn't find where to tune the version of PostgreSQL, so I just replaced /usr/bin/pg_config with a symlink to /usr/pgsql-9.5/bin/pg_config, and reinstaled psycopg2.