Per this guide:
https://support.salesforce.com/articleView?id=service_provider_define.htm&type=5
How exactly does one go about passing a RelayState parameter to a Service Provider?  Are there instructions or examples available?  If I just try to append a RelayState parameter to the login URL, then I seem to hit this issue: https://help.salesforce.com/articleView?id=000176508&type=1&language=en_US
...because the URL is not an SFDC Url, rather the Url is an external Url that is valid for the service provider.
Thoughts?

What is the best way to return a QueryLocator object that returns 0 records?
I have a Batch class that normally need to return >50K records, so I'm using the start() method that returns a QueryLocator.  However, if certain preconditions are not met, then the Batch class should not process any records -- i.e., I want the start method to return an empty result.
Options (that don't work):
1) Having start return null doesn't work as Apex throws an UnexpectedException.
2) Database.getQueryLocator(new List<SObject>()) doesn't work, as Apex requires the parameter to be a SOQL query.
3) Constructing a Database.QueryLocator object directly seems impossible.
Options (that work):
4) Execute Database.getQueryLocator() with a "bogus" SOQL query that is guaranteed to return 0 results (like, WHERE lastmodified date is in the future or some non-nullable field is null).
5) Other ideas?

What is the best way to return a QueryLocator object that returns 0 records?
I have a Batch class that normally need to return >50K records, so I'm using the start() method that returns a QueryLocator.  However, if certain preconditions are not met, then the Batch class should not process any records -- i.e., I want the start method to return an empty result.
Options (that don't work):
1) Having start return null doesn't work as Apex throws an UnexpectedException.
2) Database.getQueryLocator(new List<SObject>()) doesn't work, as Apex requires the parameter to be a SOQL query.
3) Constructing a Database.QueryLocator object directly seems impossible.
Options (that work):
4) Execute Database.getQueryLocator() with a "bogus" SOQL query that is guaranteed to return 0 results (like, WHERE lastmodified date is in the future or some non-nullable field is null).
5) Other ideas?

Hi Experts,
     I would like to know the exact difference between 15 and 18 digits record id. Most of us say, 15 digit(case sensitive) and 18 digit(case insensitive).

Let's consider a small example,
While if you query record from Developer Console you will get 18 digit record id. Consider the below retrieved 18 digit id,

001i000001AWbWuGTA(Retrieved from query)

If 18 digit case insensitive means,

001i000001AWbWugta (this id same to the above retrieved ID)? If yes, then if you queried record with this id means, you will get no result or no rows found..!

So if both 15 and 18 are unique means what is the real time use and difference between these two ID's.

Thanks in advance..!