Reproducer for slow pip resolver

Dockerfile

FROM python:3.7

WORKDIR /tmp
COPY requirements.txt ./

RUN apt-get update && apt-get install --yes time
RUN pip install -r requirements.txt

RUN pip install -U pip
RUN echo "This is the old resolver:" && time pip install -r requirements.txt

RUN echo "This is the new resolver:" && time pip install --use-feature=2020-resolver -r requirements.txt

requirements.txt

#
# This file is autogenerated by pip-compile
# To update, run:
#
#    pip-compile requirements.in
#
alembic==0.8.7            # via -r requirements.in
aniso8601==8.0.0          # via -r requirements.in, flask-restplus
apipkg==1.5               # via -r requirements.in, execnet
apispec-webframeworks==0.4.0  # via -r requirements.in
apispec[yaml]==2.0.2      # via -r requirements.in, apispec-webframeworks, flask-apispec
argh==0.26.2              # via -r requirements.in, watchdog
argon2-cffi==20.1.0       # via notebook
atomicwrites==1.2.1       # via -r requirements.in, pytest
attrs==18.2.0             # via -r requirements.in, hypothesis, pytest
babel==2.6.0              # via -r requirements.in
backcall==0.2.0           # via ipython
bcrypt==3.1.7             # via -r requirements.in, paramiko
beautifulsoup4==4.6.0     # via -r requirements.in
bleach==3.2.1             # via nbconvert
boto3==1.12.37            # via -r requirements.in
botocore==1.15.37         # via -r requirements.in, boto3, s3transfer
brotli==1.0.9             # via -r requirements.in
calltrace==0.0.4          # via -r requirements.in
certifi==2020.6.20        # via -r requirements.in, requests
cffi==1.14.3              # via -r requirements.in, argon2-cffi, bcrypt, cryptography, pynacl
chardet==3.0.4            # via -r requirements.in, requests
cherrypy==3.8.2           # via -r requirements.in
click==6.7                # via -r requirements.in, flask, rq
configobj==5.0.0          # via -r requirements.in
coverage==4.5.2           # via -r requirements.in, pytest-cov
cryptography==3.1.1       # via -r requirements.in, paramiko, pyopenssl
cx_oracle==6.4.1 ; sys_platform != "win32"  # via -r requirements.in
cython==0.29.21           # via -r requirements.in
decorator==4.4.2          # via ipython, traitlets
defusedxml==0.5.0         # via -r requirements.in, nbconvert
desktop==0.4.2            # via -r requirements.in
distro==1.4.0             # via -r requirements.in
docutils==0.15.2          # via -r requirements.in, botocore
ecdsa==0.13               # via -r requirements.in
ed25519==1.4              # via -r requirements.in
entrypoints==0.3          # via nbconvert
execnet==1.5.0            # via -r requirements.in, pytest-cache
flake8==3.5.0             # via -r requirements.in, pytest-flake8
flask-apispec==0.8.6      # via -r requirements.in
flask-restplus==0.12.1    # via -r requirements.in
flask==1.0.2              # via -r requirements.in, flask-apispec, flask-restplus
freezegun==0.3.15         # via -r requirements.in
future==0.17.1            # via -r requirements.in
giblets==0.2.1            # via -r requirements.in
hypothesis==3.88.3        # via -r requirements.in
idna==2.5                 # via -r requirements.in, requests
intset==1.0.0             # via -r requirements.in
ipykernel==5.3.4          # via ipywidgets, jupyter, jupyter-console, notebook, qtconsole
ipython-genutils==0.2.0   # via nbformat, notebook, qtconsole, traitlets
ipython==7.9.0            # via ipykernel, ipywidgets, jupyter-console
ipywidgets==7.5.1         # via jupyter
itsdangerous==1.1.0       # via -r requirements.in, flask
jedi==0.17.2              # via ipython
jinja2==2.11.1            # via -r requirements.in, flask, nbconvert, notebook
jmespath==0.9.5           # via -r requirements.in, boto3, botocore
jsonschema==2.6.0         # via -r requirements.in, flask-restplus, nbformat
jupyter-client==6.1.7     # via ipykernel, jupyter-console, notebook, qtconsole
jupyter-console==6.1.0    # via jupyter
jupyter-core==4.6.3       # via jupyter-client, nbconvert, nbformat, notebook, qtconsole
jupyter==1.0.0            # via -r requirements.in
leveldb==0.193 ; sys_platform != "win32"  # via -r requirements.in
lmdb==1.0.0               # via -r requirements.in
lxml==4.5.2               # via -r requirements.in, python-pptx
mako==1.1.3               # via -r requirements.in, alembic
markupsafe==1.1.0         # via -r requirements.in, jinja2, mako
marshmallow==2.19.5       # via -r requirements.in, flask-apispec, webargs
mccabe==0.6.1             # via -r requirements.in, flake8
mistune==0.8.4            # via nbconvert
more-itertools==8.5.0     # via -r requirements.in, pytest
msgpack-python==0.5.6     # via -r requirements.in
nbconvert==5.6.1          # via jupyter, notebook
nbformat==5.0.7           # via ipywidgets, nbconvert, notebook
ndg-httpsclient==0.5.1    # via -r requirements.in
notebook==6.1.4           # via jupyter, widgetsnbextension
numpy==1.18.5             # via -r requirements.in, pandas, scipy
openpyxl==1.6.1           # via -r requirements.in
packaging==18.0           # via -r requirements.in, bleach
pandas==0.24.2            # via -r requirements.in
pandocfilters==1.4.2      # via nbconvert
paramiko==2.7.2           # via -r requirements.in
parso==0.7.1              # via jedi
pathlib2==2.3.2           # via -r requirements.in, pytest
pathtools==0.1.2          # via -r requirements.in, watchdog
pep8==1.7.1               # via -r requirements.in, pytest-pep8
pexpect==4.8.0            # via ipython
pickleshare==0.7.5        # via ipython
pillow==3.4.1             # via -r requirements.in, python-pptx
pint==0.7.2               # via -r requirements.in
pluggy==0.8.0             # via -r requirements.in, pytest
portalocker==1.4.0        # via -r requirements.in
posix_ipc==1.0.0 ; sys_platform != "win32"  # via -r requirements.in
posix_timers==0.1.3 ; sys_platform != "win32"  # via -r requirements.in
prometheus-client==0.8.0  # via notebook
prompt-toolkit==2.0.10    # via ipython, jupyter-console
psutil==5.4.7             # via -r requirements.in
ptyprocess==0.6.0         # via pexpect, terminado
py==1.5.4                 # via -r requirements.in, pytest
pyaml==18.11.0            # via -r requirements.in
pyasn1==0.4.4             # via -r requirements.in, ndg-httpsclient
pycodestyle==2.3.1        # via -r requirements.in, flake8
pycparser==2.19           # via -r requirements.in, cffi
pyflakes==1.6.0           # via -r requirements.in, flake8, pytest-flakes
pygments==2.7.1           # via ipython, jupyter-console, nbconvert, qtconsole
pynacl==1.4.0             # via -r requirements.in, paramiko
pyopenssl==19.1.0         # via -r requirements.in, ndg-httpsclient
pyparsing==2.3.0          # via -r requirements.in, packaging
pytest-cache==1.0         # via -r requirements.in, pytest-pep8
pytest-cov==2.6.1         # via -r requirements.in
pytest-flake8==1.0.2      # via -r requirements.in
pytest-flakes==4.0.0      # via -r requirements.in
pytest-pep8==1.0.6        # via -r requirements.in
pytest==3.7.4             # via -r requirements.in, pytest-cache, pytest-cov, pytest-flake8, pytest-flakes, pytest-pep8
python-dateutil==2.7.5    # via -r requirements.in, botocore, freezegun, jupyter-client, pandas
python-editor==1.0.3      # via -r requirements.in, alembic
python-pptx==0.6.18       # via -r requirements.in
pytz==2018.7              # via -r requirements.in, babel, flask-restplus, pandas, spyne
pyyaml==3.13              # via -r requirements.in, apispec, pyaml, watchdog
pyzmq==19.0.2             # via -r requirements.in, jupyter-client, notebook, qtconsole
qtconsole==4.7.7          # via jupyter
qtpy==1.9.0               # via qtconsole
redis==2.9.1              # via -r requirements.in, rq
requests-toolbelt==0.9.1  # via -r requirements.in
requests==2.24.0          # via -r requirements.in, requests-toolbelt
rq==0.12.0                # via -r requirements.in
s3transfer==0.3.3         # via -r requirements.in, boto3
scipy==1.4.1              # via -r requirements.in
send2trash==1.5.0         # via notebook
simplejson==3.0.7         # via -r requirements.in
six==1.12.0               # via -r requirements.in, argon2-cffi, bcrypt, bleach, cryptography, flask-apispec, flask-restplus, freezegun, packaging, pathlib2, prompt-toolkit, pynacl, pyopenssl, pytest, python-dateutil, traitlets
spyne==2.13.15            # via -r requirements.in
sqlalchemy==1.3.19        # via -r requirements.in, alembic
terminado==0.8.3          # via notebook
testpath==0.4.4           # via nbconvert
tornado==6.0.4            # via ipykernel, jupyter-client, notebook, terminado
traitlets==4.3.3          # via ipykernel, ipython, ipywidgets, jupyter-client, jupyter-core, nbconvert, nbformat, notebook, qtconsole
units==0.7                # via -r requirements.in
urllib3==1.24.3           # via -r requirements.in, botocore, requests
watchdog==0.8.3           # via -r requirements.in
wcwidth==0.2.5            # via prompt-toolkit
webargs==5.5.3            # via -r requirements.in, flask-apispec
webencodings==0.5.1       # via bleach
werkzeug==1.0.1           # via -r requirements.in, flask
widgetsnbextension==3.5.1  # via ipywidgets
xlsxwriter==1.2.9         # via -r requirements.in, python-pptx
zope.component==4.6.2     # via -r requirements.in
zope.deferredimport==4.3.1  # via zope.component
zope.deprecation==4.4.0   # via zope.component
zope.event==4.5.0         # via -r requirements.in, zope.component
zope.hookable==5.0.1      # via zope.component
zope.interface==5.1.0     # via -r requirements.in, giblets, zope.component, zope.proxy
zope.proxy==4.3.5         # via zope.deferredimport