Hello. I'm testing blast to check if it could replace elasticsearch for my use case.

However I find the examples very brief and don't understand the following query example.

After reading this example, I have the following questions.

• What does _all means in the query field?
• What does the plus sign before _all means?
• How can I search inside a particular field?
• What happens if I index a type that is not defined in the mapping?
• How can I search and filter by the _type field?

Can you give me some pointers? I'll be happy to contribute by documenting these answers.