Support for pqxx 7

[Tobias-Fischer]

At the moment the project cannot be compiled with libpqxx7 as there are lots of build errors, e.g.

$SRC_DIR/ros-noetic-knowledge-representation/src/work/src/libknowledge_rep/LongTermMemoryConduitPostgreSQL.cpp:134:21: error: 'using work = class pqxx::transaction<>' {aka 'class pqxx::transaction<>'} has no member named 'parameterized'

This is because deprecated methods were removed, see e.g. jtv/libpqxx@06ee045

It would be great if you could have a look. We are trying to add knowledge-representation to RoboStack which combines ROS with Conda: RoboStack/ros-noetic#116 (this is to the PR where you will also find a full build log)

[nickswalker]

Thanks for raising this. I believe I've been seeing the deprecation warnings when building with 6.4, which is the version of libpqxx in focal/noetic. Is there a reason you're looking to use libpqxx 7? I'm not sure how to go about adopting the new query interface while maintaining compatibility with current ROS 1 releases.

[Tobias-Fischer]

I ported the newest libpqxx (7) to conda-forge and was running into problems compiling. In the meantime I back-ported libpqxx 6 to conda-forge, and using this version I can now compile knowledge-representation in RoboStack. I guess at some point Ubuntu will roll over to libpqxx 7 as well, so best to be prepared ;). You could use their defined macros to check for the version at build time: https://github.com/jtv/libpqxx/blob/master/include/pqxx/version.hxx