Improve SQL queries speed - mysql

Question

I'm using MySQL and i have schema like:
|------------|-------------|------------|--------------|
| cities |category_city| categories| companies |
|------------|-------------|------------|--------------|
| id | city_id | id | id |
| name | category_id | name |subcategory_id|
| | | parent_id | city_id |
| | | |...other cols |
|____________|_____________|____________|______________|
Relationships:
City with Category has ->belongsToMany()
public function categories()
{
return $this->belongsToMany(Category::class);
}
Categories has subcategories:
public function subcategories()
{
return $this->hasMany(Category::class, 'parent_id', 'id');
}
And i'm getting companies from category and filtering by city, because i need the current city companies and for that i have a global scope:
public function getCompanies($city_id)
{
return $this->companies()->whereHas('mainCity', function ($q) use ($city_id) {
$q->where('city_id', $city_id);
});
}
mainCity method:
public function mainCity()
{
return $this->belongsTo(City::class, 'city_id');
}
Here is my method performing the query with AJAX request:
public function getPlaces(City $city, Category $subcategory, $north, $south, $east, $west)
{
$companies = $subcategory->companies()
->withCount('comments')
->companiesByBounds($north, $south, $east, $west)
->paginate(8);
$markers = $subcategory->companies()
->companiesByBounds($north, $south, $east, $west)
->get(['lat', 'lng', 'slug', 'title']);
return response()->json(['companies' => $companies, 'markers' => $markers], 200, [], JSON_NUMERIC_CHECK);
}
and by companiesByBounds scope method:
public function scopeCompaniesByBounds($query, $north, $south, $east, $west)
{
return $query->whereBetween('lat', [$south, $north])
->whereBetween('lng', [$west, $east]);
}
In companies i have ~2m records. The main problem is that the queries taking 3.5 seconds. Help please to improve my queries.
Here is the query:
select count(*) as aggregate from `companies` where `companies`.`category_id` = '40' and `companies`.`category_id` is not null and `lat` between '53.68540097020851' and '53.749703253622705' and `lng` between '91.34262820463869' and '91.51600619536134'

Answer 1

To improve speed you need to add indexes on the columns lat and lng.
CREATE INDEX idx_lat ON companies (lat);
The indexes are used in queries when the columns are added to conditions.