issues: 855446829

This PR changes the main Dockerfile to use ubuntu:20.10 as base image instead of python:3.9.2-slim-buster (itself based on debian:buster-slim).

The Dockerfile is essentially the one from https://github.com/simonw/datasette/issues/1249#issuecomment-803698983 with some additional cleanups to slim it down.

This fixes a couple of issues: 1. The SQLite version in Debian Buster (2.6.0) doesn't support generated columns 2. Installing SpatiaLite from the Debian sid repositories has the side effect of also installing updates to libc and libstdc++ from sid.

As a bonus, the Docker image becomes smaller:

$ docker image ls REPOSITORY TAG IMAGE ID CREATED SIZE datasette 0.56-ubuntu f7aca255140a 5 hours ago 212MB datasetteproject/datasette 0.56 efb3b282f390 13 days ago 258MB

Reproduction of the first issue

``` $ curl -O https://latest.datasette.io/fixtures.db % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 260k 0 260k 0 0 489k 0 --:--:-- --:--:-- --:--:-- 489k

$ docker run -v pwd:/mnt datasetteproject/datasette:0.56 datasette /mnt/fixtures.db Traceback (most recent call last): File "/usr/local/bin/datasette", line 8, in <module> sys.exit(cli()) File "/usr/local/lib/python3.9/site-packages/click/core.py", line 829, in call return self.main(args, kwargs) File "/usr/local/lib/python3.9/site-packages/click/core.py", line 782, in main rv = self.invoke(ctx) File "/usr/local/lib/python3.9/site-packages/click/core.py", line 1259, in invoke return _process_result(sub_ctx.command.invoke(sub_ctx)) File "/usr/local/lib/python3.9/site-packages/click/core.py", line 1066, in invoke return ctx.invoke(self.callback, ctx.params) File "/usr/local/lib/python3.9/site-packages/click/core.py", line 610, in invoke return callback(args, kwargs) File "/usr/local/lib/python3.9/site-packages/datasette/cli.py", line 544, in serve asyncio.get_event_loop().run_until_complete(check_databases(ds)) File "/usr/local/lib/python3.9/asyncio/base_events.py", line 642, in run_until_complete return future.result() File "/usr/local/lib/python3.9/site-packages/datasette/cli.py", line 584, in check_databases await database.execute_fn(check_connection) File "/usr/local/lib/python3.9/site-packages/datasette/database.py", line 155, in execute_fn return await asyncio.get_event_loop().run_in_executor( File "/usr/local/lib/python3.9/concurrent/futures/thread.py", line 52, in run result = self.fn(*self.args, self.kwargs) File "/usr/local/lib/python3.9/site-packages/datasette/database.py", line 153, in in_thread return fn(conn) File "/usr/local/lib/python3.9/site-packages/datasette/utils/init.py", line 892, in check_connection for r in conn.execute( sqlite3.DatabaseError: malformed database schema (generated_columns) - near "AS": syntax error ```

Here is the SQLite version:

`` $ docker run -vpwd`:/mnt -it datasetteproject/datasette:0.56 /bin/bash root@d9220d3b95dd:/# python3 Python 3.9.2 (default, Mar 27 2021, 02:50:26) [GCC 8.3.0] on linux Type "help", "copyright", "credits" or "license" for more information.

import sqlite3 sqlite3.version '2.6.0' ```

Reproduction of the second issue

$ docker build . -t datasette --build-arg VERSION=0.55 [...snip...] The following packages will be upgraded: libc-bin libc6 libstdc++6 [...snip...] Unpacking libc6:amd64 (2.31-11) over (2.28-10) ... [...snip...] Unpacking libstdc++6:amd64 (10.2.1-6) over (8.3.0-6) ... [...snip...]

Both libc and libstdc++ are backwards compatible, so the image still works, but it will result in a combination of libraries and Python versions that exists only in the Datasette image, so it's likely untested. In addition, since Debian sid is an always-changing rolling-release, the versions of libc, libstdc++, Spatialite, and their dependencies change frequently, so the library versions in the Datasette image will depend on the day when it was built.