Laravel / MYSQL (Eloquent) - Querying large table - php

Question

I am making an online directory, this directory contains businesses, this is how the current table structure is set out:
1) "Business"
ID (PK)
Name
Phone_Number
Email
2) Tags
id (PK)
tag
3) Business_tags
id (PK)
business_id (FK)
tag_id (FK)
There are over 9k rows inside of the business table, and over 84,269 rows and there are over 29k rows inside the ("Business_tags") table (As a business can have multiple tags).
Inside the business model, is the following:
public function tags()
{
return $this->belongsToMany('App\Tags');
}
The issue is when I am trying to do a search, so for example, let's say that someone wants to search for a "Chinese" then it's takes more time than it probably should to return a value. For example, I am using:
$business = Business::where(function ($business) use ($request) {
$business->whereHas('tags', function ($tag) use ($request) {
});
})->paginate(20);
Searching takes on average: 35 seconds to display the results.
Here is the raw sql:
select * from `businesses` where (exists (select * from `tags` inner join `business_tags` on `tags`.`id` = `business_tags`.`tags_id` where `business_tags`.`business_id` = `businesses`.`id` and `name` in ('chinese')))
This takes on average: 52.4s to run inside Sequel pro (Using the raw SQL statement)
Any ideas how I can improve the performance of this query so that it's a lot faster? I want to have this functionality, but the user is not going to wait this long for a response!
EDIT:
1 PRIMARY businesses NULL ALL NULL NULL NULL NULL 8373 100.00 Using where
2 DEPENDENT SUBQUERY business_tags NULL ALL NULL NULL NULL NULL 30312 10.00 Using where
2 DEPENDENT SUBQUERY tags NULL eq_ref PRIMARY PRIMARY 4 halalhands.business_tags.tags_id 1 10.00 Using where

Answer 1

You're over-complicating this, and not using eloquent relationships correctly. You should be using JOINs instead:
$businesses = Business::join('business_tags', 'business_tags.business_id', '=', 'business.id')
->join('tags', function($join) {
$join->on('business_tags.tag_id', '=', 'tags.id')
->where('tags.name', '=', 'chinese');
})->get();
Or in raw SQL:
SELECT *
FROM `business`
INNER JOIN `business_tags` ON `business_tags`.`business_id` = `business`.`id`
INNER JOIN `tags` ON `business_tags`.`tag_id` = `tags`.`id` AND `tags`.`name` = 'chinese'
(Note that you could put that tags.name = 'chinese' part in the WHERE clause and yield the same effect)
Your current query does an exists subquery to get all the records from the pivot table that match the criteria, then passing that back to the main query. It's an extra step, and it's unnatural.
Eloquent relationships are NOT for complex queries like this, but are rather there to provide additional, related information about a record without having to write another query manually.
For instance, if you want to view a business, you might query with() phone numbers and addresses from other tables. You might want to list out their tags, or sync() them. But eloquent does not build and filter queries, that's what query builder is for.
Let me know if you need more explanation.

Answer 2

As a lot of others are also going to tell you.
Have you run EXPLAIN on your query?
Have you added indexes to your tables?
Because even with the amount of data you have mentioned the query should have been faster than what you have reported.
Also see if a JOIN can work here and if faster?(just a thought)