Thinking Sphinx group by, with distinct count - ruby-on-rails

Question

I have the following manual Sphinx query (via the mySQL client), that is producing proper results, and I would like to call it through Thinking Sphinx from Rails. For the life of me, I am struggling with how to make a 'distinct' query work in Thinking Sphinx.
mysql> select merchant_name, count (distinct part_number) from product_core group by merchant_name;
+-----------------------+-----------------------------------------+
| merchant_name | count (distinct part_number) |
+-----------------------+-----------------------------------------+
| 1962041491 | 1 |
| 3208850848 | 1 |
| 1043652526 | 48754 |
| 770188128 | 1 |
| 374573991 | 34113 |
+-----------------------+-----------------------------------------+
Please note: This mySQL query is agaist Sphinx, NOT mySQL. I use the mySQL client to connect to Sphinx, as: mysql -h 127.0.0.1 -P 9306. This works well for debugging/development. My actual db, is Postgres.
Given this, and to add more context, I am attempting to combine a group_by in thinking Sphinx, with a count('Distinct' ...).
So, this query works:
Product.search group_by: :merchant_name
... and, this query works:
Product.count ('DISTINCT part_number')
... but, this combined query throws an error:
Product.search group_by: :merchant_name, count ('DISTINCT part_number')
SyntaxError: (irb):90: syntax error, unexpected ( arg, expecting keyword_do or '{' or '('
...merchant_name, count ('DISTINCT part_num...
Both merchant_name and part_number are defined as attributes.
Environment:
Sphinx 2.2.10-id64-release (2c212e0)
thinking-sphinx 3.1.4
rails 4.2.4
postgres (PostgreSQL) 9.3.4
I have also tried using Facets, but to no avail:
Product.search group_by: :merchant_name, facets: :part_number
Product.facets :part_number, group_by: :merchant_name
For additional information, and to see if this could be accomplished through a Thinking Sphinx call, here is a basic example. I have one product table (and associated index), that lists both merchants, and their products (I agree, it could be normalized, but its coming in from a data feed, and Sphinx can handle it as is):
+-----------------+-------------------+
| merchant | product |
+-----------------+-------------------+
| Best Buy | Android phone |
| Best Buy | Android phone |
| Best Buy | Android phone |
| Best Buy | iPhone |
| Amazon | Android phone |
| Amazon | iPhone |
| Amazon | iPhone |
| Amazon | iPhone |
| Amazon | Onkyo Receiver |
+-----------------+-------------------+
With Thinking Sphinx, I want to: a) group the rows by merchant, and b) create a “distinct” product count for each group.
The above example, should give the following result:
+-----------------+------------------------+
| merchant | count(DISTINCT product |
+-----------------+------------------------+
| Best Buy | 2 |
| Amazon | 3 |
+-----------------+------------------------+

Answer 1

You're not going to be able to run this query through a model's search call, because that's set up to always return instances of a model, whereas what you're wanting is raw results. The following code should do the trick:
ThinkingSphinx::Connection.take do |connection|
result = connection.execute <<-SQL
SELECT merchant_name, COUNT(distinct part_number)
FROM product_core
GROUP BY merchant_name
SQL
result.to_a
end
Or, I think this will work to go through a normal search call:
Product.search(
select: "merchant_name, COUNT(distinct part_number) AS count",
group_by: :merchant_name,
middleware: ThinkingSphinx::Middlewares::RAW_ONLY
)