[8.x] Passthru Eloquent\Query::explain function to Query\Builder:explain for the ability to use database-specific explain commands

[tpetry]

After a twitter discussion about laravel's ability to explain database queries and the insight that many optional features are missing from the explain output for PostgreSQL, i wanted to add them to tpetry/laravel-postgresql-enhanced.

I then discovered that the eloquent builder and the query builder are using the same trait for generating explain information. As the eloquent builder is already passing many database query specific functions to the query builder i extended it to the explain command.

By this change database connections can use database-specific explain commands when they are using a custom query builder. And there is no need to change the model to make use of it. The enhanced laravel postgresql driver will use it to include many more optional explain options.

[tpetry]

I have my implementation for a PostgreSQL-specific query plan finished. The difference is remarkable. The more complex a query is, the more information my implementation will provide compared to the one of Laravel.

Laravel Query-Plan:

DB::table('migrations')->where('batch', 1)->explain()->dd();

// Output:
//array:2 [
//  0 => {#882
//    +"QUERY PLAN": "Seq Scan on migrations  (cost=0.00..11.75 rows=1 width=524)"
//  }
//  1 => {#881
//    +"QUERY PLAN": "  Filter: (batch = 1)"
//  }
//]

My Query-Plan:

DB::table('migrations')->where('batch', 1)->explain()->dd();

// Output:
// array:1 [
//  0 => """
//    Seq Scan on public.migrations  (cost=0.00..11.75 rows=1 width=524)\n
//      Output: id, migration, batch\n
//      Filter: (migrations.batch = 1)\n
//    Settings: search_path = 'public'\n
//    Planning Time: 0.370 ms
//    """
//]

With the current Laravel implementation, the new query plan is activated as soon as my enhanced driver is installed. But there's currently no way doing this as well for Eloquent queries without adding a trait to every single model. With my PR the eloquent explain() method will simply forward to the query builder explain() method as the eloquent method is not doing anything different anyways. By this any custom database connection driver can implement very specific functionality.

[mstaack]

👍🏼