RE: BUG #19411: libpq 16.x exhibits a memory leak when connections are repeatedly created and destroyed

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Please try varying the connection type and encryption.

Good idea. Here's what I found:

Test 1:
Configuration: Original (SQLAlchemy + NullPool)
libpq: 16.0.7
SQLAlchemy: Yes
Leak Rate: 803 KB/min

Test 2:
Configuration: Pure psycopg2 (default)
libpq: 16.0.7
SQLAlchemy: NO
Leak Rate: 801 KB/min

Test 3:
Configuration: Pure psycopg2 + gssencmode=disable
libpq: 16.0.7
SQLAlchemy: NO
Leak Rate: 858 KB/min

Test 4:
Configuration: Pure psycopg2 + SSL only
libpq: 16.0.7
SQLAlchemy: NO
Leak Rate: 861 KB/min

Test 5:
Configuration: Pure psycopg2
libpq: 13.0.11
SQLAlchemy: NO
Leak Rate: 17 KB/min

So, it seems none of these changes avoids the leak:
- Removing SQLAlchemy
- Disabling GSSAPI encryption
- Using SSL-only
- Changing PostgreSQL DB Server version from 16 to 13

The only changes that I found that avoid the leak are:
- Changing libpq version from 16 to 13, or
- Changing psycopg version from 2 to 3.

Tom, since your C test showed no leak, the issue is likely in how psycopg2 calls libpq, not pure libpq itself.

I guess I should report this to the psycopg2 project.