Rails displaying table data dynamically - ruby-on-rails

Question

Models
class Smoothval < ActiveRecord::Base
has_many :smoothings
has_many :steps
end
class Step < ActiveRecord::Base
belongs_to :usdzar
belongs_to :smoothing
belongs_to :smoothval
default_scope lambda {
order(id: :desc)
}
end
class Usdzar < ActiveRecord::Base
has_many :smoothings
has_many :steps
end
The index view that I am trying to achieve:
<table><thead>
<tr>
<th>Smoothing1</th>
<th>Smoothing2</th>
</tr></thead>
<tbody>
<tr>
<td>"finalsmprice","stepnum"</td>
<td>"finalsmprice","stepnum"</td>
</tr>
</tbody>
</table
So all the fsmprices and the stepnums for every smoothval from the steps table
My index.html.erb looks like this:
<h1>Listing Steps</h1>
<table class="table table-striped table-bordered table-condensed">
<thead>
<% Step.all.includes(:smoothval).group_by(&:smoothval_id).each do |smoothval_id, steps| %>
<tr>
<th>
Smoothing: <%= smoothval_id %>
</th>
</tr>
</thead>
<tbody>
<% steps.each do |step| %>
<tr>
<td>
(<%= step.fsmprice %>): <%= step.stepnum %>
</td>
<% end %>
</tr> </tbody>
<% end %>
</table>
The table is very long and obviously displays all headings and data after one another. I have tried to create a postgres pivot table but that failed using tablefunc so back trying to do it in rails
In my controller I can get the smoothvals (the table headings) into an array as follows, the array looks like [1, 5]:
sv = Smoothval.where('id IN (SELECT DISTINCT(steps.smoothval_id) FROM steps)')
#assigned = sv.pluck(:id)
How can I get the above table layout
Thanks

Answer 1

This was too difficult and came accross a post that said its best to create a pivot table
HOWEVER thats not so easy in Postgres, the issue with the tablefunc extension is that it doesnt dynamically assign the columns, so they need to be statically assigned. So I went this route for now and tested the function https://github.com/hnsl/colpivot
I stuck with the basics and did this but will need to think more about refactoring the solution.
SELECT c_crosstab('Select * from steps', 'ct_view', 'id', 'smoothval_id', 'stepnum', 'first');
SELECT *
FROM crosstab(
'SELECT usdzar_id, smoothval_id, stepnum
FROM steps
ORDER BY 1,2 ASC') -- needs to be "ORDER BY 1,2" here
AS ct ("SV" int, "Smooth1" int, "Smooth2" int, "Smooth3" int);
Hope this helps somoene else