Fix windows platform installation

[lalitpagaria]

To fix #446

@tanaysoni Please review

[tanaysoni]

Hi @lalitpagaria, thank you for the PR!

[Zenahr]

@lalitpagaria tested. Failed. We need to take care of psycopg2 as well.

Stacktrace:

Collecting psycopg2-binary
  Downloading psycopg2-binary-2.8.6.tar.gz (384 kB)
     |████████████████████████████████| 384 kB 3.3 MB/s
    ERROR: Command errored out with exit status 1:
     command: 'd:\open-source\nlp\haystack\env\scripts\python.exe' -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'C:\\Users\\STUDIUM\\AppData\\Local\\Temp\\pip-install-bvyab45q\\psycopg2-binary\\setup.py'"'"'; __file__='"'"'C:\\Users\\STUDIUM\\AppData\\Local\\Temp\\pip-install-bvyab45q\\psycopg2-binary\\setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base 'C:\Users\STUDIUM\AppData\Local\Temp\pip-pip-egg-info-lunzv2uj'
         cwd: C:\Users\STUDIUM\AppData\Local\Temp\pip-install-bvyab45q\psycopg2-binary\
    Complete output (23 lines):
    running egg_info
    creating C:\Users\STUDIUM\AppData\Local\Temp\pip-pip-egg-info-lunzv2uj\psycopg2_binary.egg-info
    writing C:\Users\STUDIUM\AppData\Local\Temp\pip-pip-egg-info-lunzv2uj\psycopg2_binary.egg-info\PKG-INFO    
    writing dependency_links to C:\Users\STUDIUM\AppData\Local\Temp\pip-pip-egg-info-lunzv2uj\psycopg2_binary.egg-info\dependency_links.txt
    writing top-level names to C:\Users\STUDIUM\AppData\Local\Temp\pip-pip-egg-info-lunzv2uj\psycopg2_binary.egg-info\top_level.txt
    writing manifest file 'C:\Users\STUDIUM\AppData\Local\Temp\pip-pip-egg-info-lunzv2uj\psycopg2_binary.egg-info\SOURCES.txt'

    Error: pg_config executable not found.

    pg_config is required to build psycopg2 from source.  Please add the directory
    containing pg_config to the $PATH or specify the full executable path with the
    option:

        python setup.py build_ext --pg-config /path/to/pg_config build ...

    or with the pg_config option in 'setup.cfg'.

    If you prefer to avoid building psycopg2 from source, please install the PyPI
    'psycopg2-binary' package instead.

    For further information please check the 'doc/src/install.rst' file (also at
    <https://www.psycopg.org/docs/install.html>).

    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

[Zenahr]

@lalitpagaria It might be worth considering adding psycopg2-binary instead of psycopg2 to the dependencies. However, I remember I had trouble installing it using that and reserved to building it from source. I can put up a working repository with my working windows setup. Including the requirements.txt file of course if that helps.

For some reason running pip install psycopg2-binary on it's own leads to the same trace from above.

Apparently this is a known issue

[lalitpagaria]

@Zenahr Thank you for testing out. I just pushed another change and removed psycopg2-binary and uvloop form the requirements file, as these are not used inside haystack code base. From history what found that older version of farm had these dependencies (by checking Tutorial6_Better_Retrieval_via_DPR.ipynb)

[Zenahr]

lgtm

[lalitpagaria]

lgtm

@tanaysoni fyi

[tanaysoni]

Thanks again for working on this @lalitpagaria & @Zenahr. I re-added uvloop as a conditional requirement as it might be useful when running the REST APIs.