Ecto order_by text field

Kolawole O. Gabriel — Thu, 19 Nov 2020 22:07:50 +0000

This post demonstrates how to order an ecto query by a text field.
by sending the order raw sql query through Ecto.Query.API.fragment/1

Sample table

Assuming we want to query a table containing a list of scheduled jobs with known statuses. e.g
RUNNING, PENDING, COMPLETED, FAILED

id	task_ref	status	last_exec_timestamp
1	2232323	PENDING	1605726253
2	2232324	FAILED	1605726153
4	2132326	RUNNING	1605726233
5	2032326	RUNNING	1605726233
6	2932326	FAILED	1605726233
7	2233326	COMPLETED	1605726233
8	2238326	FAILED	1605726233

Our objective is to:

Fetch all rows
Order the rows in the following order RUNNING > PENDING > COMPLETED > FAILED

Off we go

 #SomeModule
 import Ecto.Query

 @statuses_order """
    (case(?)
      when 'RUNNING' then 1
      when 'PENDING' then 2
      when 'COMPLETED' then 3
      else 4
    end)
  """
 def your_function do
    from(j in Jobs)
    |> order_by([j], asc: fragment(@statuses_order, j.status))
    |> Repo.all()
 end

Just like that our jobs will be returned in the order which we have specified in the @statuses_order module attribute.

More information about this subject from elixir forum can be found here.

Thats it! :)

Getting rid of specific git commits

Kolawole O. Gabriel — Sun, 04 Oct 2020 09:09:29 +0000

There are two possible reasons (that I can think of) you might want to revert a commit or specific commits:

Scenario A: When working on a feature branch and you later realize a specific change is no longer relevant and you want to remove such commit/change.

Scenario B: When you pushed a working branch to remote, just about to a create a pull request, you compared your branch and realize you have commits that are not related to your work, probably due to the local repository being out of sync.

How to fix ?

In the case of Scenario A; we can execute the following:

git revert <commit-hash>

where <commit-hash> is the targeted commit hash, done.

Hint, we can list all commits together with their hash by executing

git log --oneline

Scenario B: where we need to remove multiple commits/changes from our branch, we can rebase interactively with a target base branch by executing

git rebase -i <target-branch>

This will result into an opened editor listing all the commits in the current working branch.

Hint, rebase entails taking the current changes and stacking it on top of another branch, hence we can selectively pick the commits desired and reject others.

With the editor opened, we can go ahead and remove specific commits as desired by simply deleting their records in the opened editor. There are instructions as to applicable commands in the editor.

The opened editor with commands, should look like this:

# Commands:
# p, pick = use commit
# r, reword = use commit, but edit the commit message
# e, edit = use commit, but stop for amending
# s, squash = use commit, but meld into previous commit
# f, fixup = like "squash", but discard this commit's log message
# x, exec = run command (the rest of the line) using shell
# d, drop = remove commit

On completing the exercise and closing the editor, the rebase will work its way automatically.

That is it. Fun coding!

DEV Community: Kolawole O. Gabriel

Ecto order_by text field

Sample table

Getting rid of specific git commits