How to do full text search in a Ruby on Rails app on Heroku, without having to pay for their full text search add-ons, using some workarounds for problems in the pg_search gem.

1. Full-Text Search
on Heroku . . .
FOR FREE!
(by working around bogons in pg_search)
by Dave Aronson, T. Rex of Codosaurus, LLC

2. What's the Problem?
:-) Heroku gives lots of stuff for free.
:-( But not its full-text search add-ons.
:-) But we still have the database.
:-( But using LIKE for that, sucks.
:-) But PostgreSQL has full text search.
:-( But that feature is a royal pain to use.
:-) But the pg_search gem makes it easy.
:-( But its scopes have problems.
:-) But I've figured out workarounds.

3. Example: Job Model
class JobsController < ApplicationController
def index # also serves as a search screen
@jobs = Job.in_category(params[:category]).
desc_has(params[:desc]).
in_state(params[:state]).
title_has(params[:title])
# quick and dirty example,
# ignoring order and pagination
end
end

4. Making pg_search_scopes
class Job < ActiveRecord::Base
include PgSearch
attr_accessible :category, :desc, :state, :title
scope :in_category, lambda { |cat|
where(category: cat) if cat.present? }
pg_search_scope :desc_has, against: :desc
scope :in_state, lambda { |st|
where(state: st) if st.present? }
pg_search_scope :title_has, against: :title
end

5. Bogon #1: Not Optional
- Fails SILENTLY (as far as user knows) --
no results; only clue is in logs/screen:
Started GET "/jobs" [...]
Processing by JobsController#index as HTML
NOTICE: text-search query doesn't contain lexemes: ""
LINE 1: ...glish', coalesce("jobs"."desc"::text, ''))) @@
('')))
- "query doesn't contain lexemes" means:
"I need something to search for".

6. Fix: Wrap it up, I'll take it
class Job < ActiveRecord::Base
include PgSearch
attr_accessible :category, :desc, :state, :title
scope :in_category, lambda { |cat|
where(category: cat) if cat.present? }
scope :desc_has, lambda { |desc|
_desc_has(desc) if desc.present? }
scope :in_state, lambda { |st|
where(state: st) if st.present? }
scope :title_has, lambda { |ttl|
_title_has(ttl) if ttl.present? }
private
pg_search_scope :_desc_has, against: :desc
pg_search_scope :_title_has, against: :title
end

7. Bogon #2: ONE per Query!
ActiveRecord::StatementInvalid in Jobs#index
Showing /Users/dave/jobboard/app/views/jobs/index.html.erb where line #49 raised:
PG::Error: ERROR: ORDER BY "pg_search_rank" is ambiguous
LINE 1: ...nglish', ''' ' || 'senator' || ' ''')))) ORDER BY pg_search_...
^
- I didn't ask for pg_search_rank!
- Look at the generated SQL:
SELECT "jobs".*, ([gobbledygook]) AS
pg_search_rank, "jobs".*, ([similar
gobbledygook]) AS pg_search_rank FROM
"jobs" WHERE ([more gobbledygook]) ORDER
BY pg_search_rank DESC, "jobs"."id" ASC
- It doesn't know which one we want!

8. Wrong Fix: add .order
class JobsController < ApplicationController
def index # also serves as a search screen
@jobs = Job.in_category(params[:category]).
desc_has(params[:desc]).
in_state(params[:state]).
title_has(params[:title]).
order(:id)
end
end
- Generated SQL now ends in:
ORDER BY pg_search_rank DESC,
"jobs"."id" ASC, id
- Didn't clear; just tacked it on!

9. Right Fix: add .reorder
class JobsController < ApplicationController
def index # also serves as a search screen
@jobs = Job.in_category(params[:category]).
desc_has(params[:desc]).
in_state(params[:state]).
title_has(params[:title]).
reorder(:id)
end
end
- Generated SQL now ends in:
ORDER BY id
- No longer barfs; query now works right.

10. Summary
To do full-text search for free on Heroku,
you can use pg_search, BUT...
To make its scopes optional, wrap them in
normal scopes with no-argument detection
To use two or more in one query, tack
.reorder onto the query, using a
non-ambiguous column or value

11. Questions/Contact/Etc.
Any questions?
Contact information:
YourNameHere.2.trex [at] codosaur [dot] us
(yes, put your name there, without spaces, punctuation, etc.)
+1-571-308-6622
http://www.codosaur.us/ (main site)
http://blog.codosaur.us/ (code blog) Brought to
http://www.dare2XL.com/ (excellence blog) you by
Codosaurus,
http://linkedin.com/in/davearonson LLC
http://facebook.com/dare2xl
@davearonson