PHPORM-215 Implement Schema::getColumns and getIndexes

[GromNaN]

Fix PHPORM-215

This method is used by the command db:table:

Example of output:

php artisan db:table --database=mongodb users

  users .............................................................................................................  
  Columns ......................................................................................................... 8  
  Size ..................................................................................................... 60.00 KB  

  Column ....................................................................................................... Type  
  _id objectId ............................................................................................. objectId  
  created_at date, nullable .................................................................................... date  
  email string, nullable ..................................................................................... string  
  email_verified_at date, nullable ............................................................................. date  
  name string, nullable ...................................................................................... string  
  password string, nullable .................................................................................. string  
  remember_token string, nullable ............................................................................ string  
  updated_at date, nullable .................................................................................... date  

  Index .............................................................................................................  
  _id_ _id ......................................................................................... default, primary  
  email_1 email ..................................................................................... default, unique  

Checklist

• Add tests and ensure they pass
• Add an entry to the CHANGELOG.md file
• Update documentation for new features

[alcaeus]

This method could get slow for larger collections, so it may be worth adding a $sample pipeline stage down the road.

Depending on how much the feature is used, we can also consider expanding its functionality in a separate project to be more similar to Compass' schema analysis feature. For now, the current solution provides a good starting point.

[GromNaN]

I don't think we should try to replicate what is done by Compass. I added $sample and $limit stages.

[GromNaN]

I tried on atlas sample dataset sample_airbnb.listingsAndReviews. With $sample, I get this error:

  PlanExecutor error during aggregation :: caused by :: Sort exceeded memory limit of 33554432 bytes, but did not opt in to external sorting. Aborting operation. Pass allowDiskUse:true to opt in.

It works without it. There might be an optimization on the server for this use-case.