Tutorial for Append Only Database/Log

[Danwhy]

Adds basic guide for creating a schema and a behaviour to facilitate an append only database, with code and tests.

There are still some improvements/advancements that could be made to the guide (see open questions in #1), but this should be a good starting point

[nelsonic]

@Danwhy I'm going to take a look at this tonight.
please remove "[WiP]" if you feel it's "mergeable". thanks! 👍

Following along ...

Create SQL user:

Install deps

Create Database:

Migrate:

So far, so fail:

👍

[nelsonic]

test add item to database (Append.AddressTest)
     test/append/address_test.exs:5
     ** (UndefinedFunctionError) function Repo.insert/1 is undefined (module Repo is not available)

😞

[Danwhy]

Should have alias Append.Repo on this line. Sorry @nelsonic! I'll add it in

[nelsonic]

No worries. don't apologize. you've done a great job with this guide (so far!) 🎉
(thanks! hope you're feeling much better!)

[nelsonic]

Have to add:

  alias Append.Repo

To the top of lib/append/append_only_log.ex
as per: https://github.com/dwyl/phoenix-ecto-append-only-log-example/pull/2/files#diff-ba1c4c1b3f67bc03f7691e3253abce7dR2

then tests will pass:

adding to code/instructions in README.md 😉

[nelsonic]

unclear why we need to remove the :id
is it not auto-incremented by Postgres when the record is inserted?

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@165818e). Click here to learn what that means.
The diff coverage is 56.75%.

@@            Coverage Diff            @@
##             master       #2   +/-   ##
=========================================
  Coverage          ?   56.75%           
=========================================
  Files             ?       11           
  Lines             ?       37           
  Branches          ?        0           
=========================================
  Hits              ?       21           
  Misses            ?       16           
  Partials          ?        0

Impacted Files	Coverage Δ
test/support/channel_case.ex	0% <0%> (ø)
lib/append_web.ex	0% <0%> (ø)
lib/append_web/views/error_helpers.ex	0% <0%> (ø)
lib/append/address.ex	100% <100%> (ø)
test/support/conn_case.ex	100% <100%> (ø)
lib/append_web/controllers/page_controller.ex	100% <100%> (ø)
lib/append_web/views/error_view.ex	100% <100%> (ø)
lib/append_web/endpoint.ex	50% <50%> (ø)
test/support/data_case.ex	57.14% <57.14%> (ø)
lib/append_web/router.ex	66.66% <66.66%> (ø)
... and 1 more

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[nelsonic]

should this be an {:ok, history} = Address.get_history(updated_item) tuple pattern match?
or does Repo.all(query) always return a List (even if it's empty) ?

[nelsonic]

@Danwhy this is an excellent start.
I was able to follow along on my localhost without any issues (other than those described/fixed above):

Happy to merge this so others can benefit from it.
And we can iterate on it further when we have time.

@Cleop do you prefer to try follow the steps in PR/branch form or can I merge to master ?

Thanks again! ❤️ ✅

[Cleop]

Feel free to merge @nelsonic, I'll create a separate PR from master for a couple of tweaks. Nice one @Danwhy 🎉

[nelsonic]

@Cleop thanks. 👍

[nelsonic]

Note: we still need to add the answers to the "intro questions": #1 (comment)

I'm going to add those to a separate PR shortly.
Merging this for now. 👍