Show filterable rows count - sql

Question

These are my tables:
CREATE TABLE product (
product_id serial PRIMARY KEY,
name VARCHAR ( 50 ),
size VARCHAR ( 50 ),
)
CREATE TABLE country (
country_id serial PRIMARY KEY,
name VARCHAR ( 50 ),
product_id INT
)
CREATE TABLE color (
color_id serial PRIMARY KEY,
name VARCHAR ( 50 ),
product_id INT
)
I want my query to return the list of product in this way.
Query result needs to have to objects: meta and result
The result needs to be paginated with 10 objects. And meta should include the total count of filtered products, count of attributes of products.
When country is filtered, I want to see other country choices' names and counts as well, not only the country filtered (same for the color).
If the color is filtered, I don't want to see the countries that are not available with this color for the products we have (and vice versa):
{
"meta": {
"count" : 200,
"next_page": true,
"colors": [
{"id": 1, "name": "red", "count": 5},
{"id": 2, "name": "white", "count": 10}
],
"countries": [
{"id": 1, "name": "Germany", "count": 120},
{"id": 2, "name": "Albania", "count": 201}
],
"sizes": [
{"id": 1, "name": "Big", "count": 45},
{"id": 2, "name": "Small", "count": 63}
]
},
"result": [
{
"product_name" : "Milk",
"color": "White",
"country": "Germany"
},
{
"product_name" : "Milk2",
"color": "White",
"country": "Germany"
},
{
"product_name" : "Milk3",
"color": "White",
"country": "Germany"
}
]
}
This is what I've done:
WITH results as (
SELECT
product.id,
product.name,
product.size,
color.name,
country.name
FROM product
LEFT JOIN color ON color.product_id = product.id
LEFT JOIN country ON country.product_id = product.id
WHERE color.name = ANY('{White}')
)
SELECT
(
SELECT
jsonb_build_object(
'count', count.full_count,
'next_page', count.full_count - (1 * 10) > 0
)
FROM (SELECT count(id) AS full_count FROM results) AS count
) AS meta,
(
SELECT jsonb_agg(result_rows)
FROM
(SELECT * FROM results
LIMIT 10
OFFSET (1-1) * 10) AS result_rows
) AS result
I've tried lot's of thing and did not get the result of getting name and counts of country and colors. So I didn't include that part of query. BTW, the the slight change in query returning result is acceptable.
Any help is highly appreciated. I'm using the latest version of PostgreSQL. You can see this type of query used in Ebay (search results page) where page filter properties change while you select different filters to correspond the available choices and counts depending your current filters.

Answer 1

First of all, your data model looks like strange (or wrong). I would suggest you the following data model instead, so that you can store several products with the same size and/or the same color and/or the same country. The only limitation here is that one product may only have one size, one color, and one country. You will have to create new tables if you want to manage one to many relationships.
CREATE TABLE size (
size_id serial PRIMARY KEY,
name VARCHAR ( 50 )
) ;
CREATE TABLE country (
country_id serial PRIMARY KEY,
name VARCHAR ( 50 )
) ;
CREATE TABLE color (
color_id serial PRIMARY KEY,
name VARCHAR ( 50 )
) ;
CREATE TABLE product (
product_id serial PRIMARY KEY,
name VARCHAR ( 50 ),
size_id INT CONSTRAINT rf_size REFERENCES size (size_id) MATCH SIMPLE,
color_id INT CONSTRAINT rf_color REFERENCES color (color_id) MATCH SIMPLE,
country_id INT CONSTRAINT rf_country REFERENCES country (country_id) MATCH SIMPLE
) ;
Then you can get your expected with the following query :
WITH global_list AS (
SELECT p.size_id, p.color_id, p.country_id
, s.name AS size_name, clr.name AS color_name, cty.name AS country_name
, count(*) AS product_count
FROM product AS p
INNER JOIN country AS cty
ON cty.country_id = p.country_id
INNER JOIN color AS clr
ON clr.color_id = p.color_id
INNER JOIN size AS s
ON s.size_id = p.size_id
GROUP BY p.size_id, size_name, p.color_id, color_name, p.country_id, country_name
), result_list AS (
SELECT jsonb_build_object('product_name',p.name,'color',clr.name,'country',cty.name, 'size', s.name) AS result
, count(*) OVER () AS total_count
FROM product AS p
INNER JOIN country AS cty
ON cty.country_id = p.country_id
INNER JOIN color AS clr
ON clr.color_id = p.color_id
INNER JOIN size AS s
ON s.size_id = p.size_id
WHERE cty.name = COALESCE('Albania', cty.name) -- enter here the country filter criteria if any, like 'Germany', or NULL if no country criteria
AND clr.name = COALESCE(NULL, clr.name) -- enter here the color filter criteria if any, like 'White', or NULL if no color criteria
AND s.name = COALESCE(NULL, s.name) -- enter here the size filter criteria if any, like 'Medium', or NULL if no size criteria
), country_list AS (
SELECT jsonb_build_object('id', gl.country_id, 'name', gl.country_name, 'count', sum(gl.product_count)) AS country
FROM global_list AS gl
WHERE gl.color_name = COALESCE(NULL, gl.color_name) -- same color criteria than above
AND gl.size_name = COALESCE(NULL, gl.size_name) -- same size criteria than above
GROUP BY gl.country_id, gl.country_name
), color_list AS (
SELECT jsonb_build_object('id', gl.color_id, 'name', gl.color_name, 'count', sum(gl.product_count)) AS color
FROM global_list AS gl
WHERE gl.country_name = COALESCE('Albania', gl.country_name) -- same country criteria than above
AND gl.size_name = COALESCE(NULL, gl.size_name) -- same size criteria than above
GROUP BY gl.color_id, gl.color_name
), size_list AS (
SELECT jsonb_build_object('id', gl.size_id, 'name', gl.size_name, 'count', sum(gl.product_count)) AS size
FROM global_list AS gl
WHERE gl.country_name = COALESCE('Albania', gl.country_name) -- same country criteria than above
AND gl.color_name = COALESCE(NULL, gl.color_name) -- same color criteria than above
GROUP BY gl.size_id, gl.size_name
)
SELECT (SELECT jsonb_build_object('result', jsonb_agg(result)) FROM result_list LIMIT 10 OFFSET 0)
|| jsonb_build_object('meta'
, jsonb_build_object( 'count', (SELECT total_count FROM result_list LIMIT 1)
, 'next_page', (SELECT total_count > 10 FROM result_list LIMIT 1)
, 'countries', (SELECT jsonb_agg(country) FROM country_list)
, 'colors', (SELECT jsonb_agg(color) FROM color_list)
, 'sizes', (SELECT jsonb_agg(size) FROM size_list)
)
)
ps : the first query Global_list could be implemented as a view
The result looks like :
{
"meta": {
"count": 2,
"sizes": [
{
"id": 1,
"name": "Small",
"count": 1
},
{
"id": 2,
"name": "Medium",
"count": 1
}
],
"colors": [
{
"id": 1,
"name": "White",
"count": 1
},
{
"id": 3,
"name": "Blue",
"count": 1
}
],
"countries": [
{
"id": 1,
"name": "Germany",
"count": 1
},
{
"id": 3,
"name": "Albania",
"count": 2
}
],
"next_page": false
},
"result": [
{
"size": "Medium",
"color": "White",
"country": "Albania",
"product_name": "Milk2"
},
{
"size": "Small",
"color": "Blue",
"country": "Albania",
"product_name": "Milk3"
}
]
}
All details in dbfiddle