Module: SqliteExt

Defined in:
lib/sqlite_ext.rb,
lib/sqlite_ext/version.rb,
lib/sqlite_ext/init_injection.rb,
lib/sqlite_ext.rb

Defined Under Namespace

Modules: InitInjection

Constant Summary collapse

VERSION = 
'1.0.0'

Class Method Summary collapse

Class Method Details

.enhance_db_session(db) ⇒ Object

Creates all of the registered functions on an instance of ‘SQLite3::Database`.

This is normally called automatically for each new instance, but it can also be used to add the functions to an instance that was created before the functions were registered.



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# File 'lib/sqlite_ext.rb', line 145

def enhance_db_session(db)
  registered_function_creations.each_value do |(args,block)|
    db.create_function *args, &block
  end
end

.purge_function_registrations ⇒ Object

Removes all function registrations. Has no effect on existing instances of ‘SQLite3::Database`.



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# File 'lib/sqlite_ext.rb', line 134

def purge_function_registrations
  registered_function_creations.clear
end

.register_create_function(name, arity, *other_args, &block) ⇒ Object

Registers a #create_function call to be invoked on every new instance of ‘SQLite3::Database` immidately after it is instantiated and before it is returned from the call to `.new` and before the invocation of a block that is passed to `.new`.

The parameters passed to ‘#register_create_function` are exactly the same as those that would be passed to `SQLite3::Database#create_function`.

Note that this only affects instances of ‘SQLite3::Database` that are subsequently created and has no effect on previously created instances.

Example:

SqliteExt.register_create_function ‘sqrt’, 1 do |fn,x|

fn.result =
  case x
    when nil then nil
    else Math.sqrt(x)
    end
  end

SQLite3::Database.new ‘data.db’ do |db|

puts db.execute("SELECT sqrt(25)")[0][0]

end # Output: 5.0



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# File 'lib/sqlite_ext.rb', line 118

def register_create_function(name, arity, *other_args, &block)
  name = "#{name}"
  registered_function_creations[name] = [
    [name, arity, *other_args],
    block
  ]
end

.register_function(name, prok) ⇒ Object

Registers a Ruby ‘Proc` to be used as a function in SQL code executed through subsequent new instances of `SQLite3::Database`.

When ‘NULL` value is passed 1 or more of the `Proc`’s required parameters, it will be “propagated”, meaning that the specified ‘Proc` will not be invoked and `NULL` will be returned from the call in SQL.

When non-‘NULL` values are passed to all of the `Proc`’s required parameters and ‘NULL` is passed to any or all of the `Proc`’s optional parameters, they will NOT be propagated, and the ‘Proc` WILL be invoked. Values passed as `NULL` in SQL will be forwarded to the `Proc` as Ruby `nil`s.

Whenever the ‘Proc` is called and returns `nil`, that will result in `NULL` being returned from the function call in SQL.

Example:

SqliteExt.register_function(

'sqrt',
->(x){ Math.sqrt(x) }

)

SQLite3::Database.new ‘data.db’ do |db|

puts db.execute(
  "SELECT sqrt(25), COALESCE(sqrt(NULL), -1)"
).first

end

# == Output == # 5.0 # -1



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# File 'lib/sqlite_ext.rb', line 56

def register_function(name, prok)
  minimum_arity =
    prok.
    parameters.select{ |(kind,_)| kind == :req }.
    count

  register_create_function name, minimum_arity do |fn,*args|
    fn.result =
      if args[0...minimum_arity].any?{ |a| a.nil? }
        nil
      else
        prok.call(*args)
      end
  end
end

.register_ruby_math ⇒ Object

Registers most of the public module methods of Ruby’s ‘Math` module to be used as a functions in SQL code executed through subsequent new instances of `SQLite3::Database`.

The ‘Math.frexp` method is omitted becuse it returns an array, and there is no way to return an array from a SQL function in SQLite.

‘NULL`s are propagated as described in the documentation for `register_function`.



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# File 'lib/sqlite_ext.rb', line 82

def register_ruby_math
  fn_methods = Math.public_methods - (Module.instance_methods << :frexp)
  fn_methods.each do |m|
    register_function m, Math.method(m)
  end
end

.registered_function_names ⇒ Object

Returns an array of the names of all currently registered functions.



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# File 'lib/sqlite_ext.rb', line 128

def registered_function_names
  registered_function_creations.keys
end