Alan Coromano questions

• How long is it ok to keep a connection to a MySql db open?
• Available types for Ruby's hash key
• Making the peace of the code immutable
• Trying to create a map dynamically
• Access to nested map's values
• Unable to find SBT plugin for IntelliJ Idea 12
• MongoDb - "join" or $in two collections
• Adding a validation error in a controller in Rails 4
• Android XML Naming convention [duplicate]
• .gitignore Doesn't Seem To Work

Alan Coromano answers