Class: Cursor

Inherits:
Object
  • Object
show all
Defined in:
lib/has_helpers/cursor.rb

Overview

Encapsulates cursor database functionality. Currently only works with PostgreSQL.

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name: random_name, connection: ActiveRecord::Base.connection, sql:) ⇒ Cursor

Returns a new instance of Cursor.



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# File 'lib/has_helpers/cursor.rb', line 20

def initialize(name: random_name, connection: ActiveRecord::Base.connection, sql:)
  @name = name
  @connection = connection
  @sql = sql
end

Class Method Details

.execute(**cursor_args, &block) ⇒ Object

Example

Cursor.execute(sql: "SELECT * FROM users") do |cursor| while user = cursor.next() do ... end end



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# File 'lib/has_helpers/cursor.rb', line 12

def self.execute(**cursor_args, &block)
  cursor = Cursor.new(**cursor_args)
  cursor.declare!
  block.call(cursor)
ensure
  cursor.close!
end

Instance Method Details

#close! ⇒ Object 



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# File 'lib/has_helpers/cursor.rb', line 30

def close!
  @connection.execute "CLOSE #{@name};"
end

#declare! ⇒ Object 



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# File 'lib/has_helpers/cursor.rb', line 26

def declare!
  @connection.execute "DECLARE #{@name} CURSOR WITH HOLD FOR #{@sql};"
end

#next(n = 1) ⇒ Object

Fetches the next n records from the cursor. Returns nil if there are no records left.



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# File 'lib/has_helpers/cursor.rb', line 36

def next(n = 1)
  result = @connection.execute("FETCH #{n} FROM #{@name};")
  n == 1 ? result.first : result.to_a.presence
end