Parslet SQL parser practice

gistfile1.rb

require 'parslet'
require 'pp'
require 'yaml'

class P < Parslet::Parser
  root(:table_definition)

  rule(:space) { match('\s') }
  rule(:space?) { space.maybe }
  rule(:spaces) { space.repeat(1) }
  rule(:spaces?) { spaces.maybe }

  rule(:comma) { str(',') }

  rule(:table_definition) do
    create_table >>
      spaces? >>
      str('(') >>
      spaces? >>
      column_definitions >>
      spaces? >>
      table_constraints
  end

  rule(:create_table) do
    spaces? >>
      str('CREATE TABLE') >>
      spaces? >>
      table_name
  end

  rule(:table_name) do
    identifier >>
      str('.') >>
      identifier
  end

  rule(:column_definitions) do
    column_definition.repeat
  end

  rule(:column_definition) do
    spaces? >>
      identifier >>
      spaces? >>
      type >>
      spaces? >>
      column_constraints.repeat >>
      comma >>
      spaces?
  end

  rule(:identifier) do
    str('"') >>
      match('[^"]').repeat(1) >>
      str('"') >>
      spaces?
  end

  rule(:type) do
    type_varchar2 | date | number | char
  end

  rule(:type_varchar2) do
    str("VARCHAR2") >>
      str('(') >>
      match(['[0-9]']).repeat(1) >>
      str(')')
  end

  rule(:date) do
    str('DATE')
  end

  rule(:number) do
    str('NUMBER') >>
      str('(') >>
      match('[0-9]').repeat(1) >>
      str(',') >>
      match('[0-9]').repeat(1) >>
      str(')')
  end

  rule(:char) do
    str("CHAR") >>
      str('(') >>
      match('[0-9]').repeat(1) >>
      str(')')
  end

  # 列制約
  rule(:column_constraints) do
    (
      column_constraint_not_null | column_constraint_enable | column_constraint_default_zero
    ) >> spaces?
  end

  rule(:column_constraint_not_null) do
    str('NOT NULL')
  end

  rule(:column_constraint_enable) do
    str('ENABLE')
  end

  rule(:column_constraint_default_zero) do
    str('DEFAULT 0')
  end

  # 表制約
  rule(:table_constraints) do
    spaces? >>
      str('CONSTRAINT') >>
      spaces? >>
      identifier >>
      spaces? >>
      table_constraint_primary_key
  end

  rule(:table_constraint_primary_key) do
    str('PRIMARY KEY') >>
      spaces? >>
      str('(') >>
      comma_separated_identifiers >>
      str(')')
  end

  rule(:comma_separated_identifiers) do
    (identifier >> spaces? >> comma.maybe >> spaces?).repeat
  end
end