How to query across multiple rows in postgres - postgresql

Question

I'm saving dynamic objects (objects of which I do not know the type upfront) using the following 2 tables in Postgres:
CREATE TABLE IF NOT EXISTS objects(
id UUID NOT NULL DEFAULT gen_random_uuid(),
user_id UUID NOT NULL,
name TEXT NOT NULL,
PRIMARY KEY(id)
);
CREATE TABLE IF NOT EXISTS object_values(
id UUID NOT NULL DEFAULT gen_random_uuid(),
event_id UUID NOT NULL,
param TEXT NOT NULL,
value TEXT NOT NULL,
);
So for instance, if I have the following objects:
dog = [
{ breed: "poodle", age: 15, ...},
{ breed: "husky", age: 9, ...},
}
monitors = [
{ manufacturer: "dell", ...},
}
It will live in the DB as follows:
-- objects
| id | user_id | name |
|----|---------|---------|
| 1 | 1 | dog |
| 2 | 2 | dog |
| 3 | 1 | monitor |
-- object_values
| id | event_id | param | value |
|----|----------|--------------|--------|
| 1 | 1 | breed | poodle |
| 2 | 1 | age | 15 |
| 3 | 2 | breed | husky |
| 4 | 2 | age | 9 |
| 5 | 3 | manufacturer | dell |
Note, these tables are big (hundreds of millions). Generally optimised for writing.
What would be a good way of querying/filtering objects based on multiple object params? For instance: Select the number of all husky dogs above the age of 10 per unique user.
I also wonder whether it would have been better to denormalise the tables and collapse the params onto a JSON column (and use gin indexes).
Are there any standards I can use here?

Answer 1

"Select the number of all husky dogs above the age of 10 per unique user" - The following query would do it.
SELECT user_id, COUNT(DISTINCT event_id) AS num_husky_dogs_older_than_10
FROM objects o
INNER JOIN object_values ov
ON o.id_ = ov.event_id
AND o.name_ = 'dog'
GROUP BY o.user_id
HAVING MAX(CASE WHEN ov.param = 'age'
AND ov.value_::integer >= 10 THEN 1 END) = 1
AND MAX(CASE WHEN ov.param = 'breed'
AND ov.value_ = 'husky' THEN 1 END) = 1;
Since your queries are most likely affected by having always the same JOIN operation between these two tables on the same fields, would be good to have a indices on:
the fields you join on ("objects.id", "object_values.event_id")
the fields you filter on ("objects.name", "object_values.param", "object_values.value_")
Check the demo here.