libpq-dev
Overview
The libpq-dev
library is built following Debian's libpq-dev package
idea: it contains a minimal set of PostgreSQL binaries and headers required
for building 3rd-party applications for PostgreSQL.
Moreover this package provides even smaller subset of binaries than Debian's libpq-dev package and was designed this way on purpose. The main goal is to provide all requirements for building Psycopg2.
This package is meant to be built as platform-specific binary Python wheels, contains only PostgreSQL binaries and 0 Python code.
Rationale
The Psycopg2 library is built as a wrapper around libpq
and mostly
written in C. It is distributed as an sdist
and being built during
installation. For this reason it requires some PostgreSQL binaries and
headers to be present during installation.
For simple environments where database server and application server combine the same host it is not an issue but it might be a different case for distributed systems. This leads to the need to install some of PostgreSQL binaries on the application server as well.
On top of that there might be a situation when single application server needs
to host several applications that use different versions of PostgreSQL and
thus Psycopg2 needs to be built against different versions of libpq
.
Contents
The package contains:
- pg_config
- libpq.a (static build of
libpq
)- a number of additional headers
For full list of files please take a look into setup.cfg/[files]/data_files
.
Once more, 0 Python sources or any other stuff.
Usage
The usage is pretty simple and straight forward: install libpq-dev
of
required version (the same version as your PostgreSQL version) before
installing Psycopg2.
$ pip install libpq-dev==9.4.3 $ pip install psycopg2
Please note that Psycopg2 prefers static linking against libpq
so if you
distributing your application and all its dependencies with wheels or something
like Platter then you don't need need to ship libpq-dev
as long as you
have Psycopg2 wheel built with it.
Limitation and Known Issues
Currently libpq-dev
is being built only for Linux
with
Python 2.7, 3.3, 3.4
from PostgreSQL 9.* sources.
If there will be demand for other platforms, Python versions or older PostgreSQL versions new builds will be added.
Also please note that there is known issue with PIP and some Python packages (including Psycopg2) that doesn't allow you to do:
$ pip install libpq-dev==9.4.3 psycopg2
or put these names into requirements.txt and then run pip install -r
requirements.txt
. This is because Psycopg2 requires pg_config
and
other PostgreSQL binaries to be present in order to run egg_info
command
(which is executed by PIP during normal installation process).
Unfortunately there is nothing we can do about it right now but we hope that either this will be handled somehow in future PIP releases or fixed in Psycopg2.
Further Development
We assume that there might be demand in builds for additional platforms or Python versions.
Also there may be other Python libraries that may be used with this package. In case this package is missing some binaries requried by libraries other that `Pscyopg2`_ they will be added.