Class: ActiveRecord::ConnectionAdapters::JdbcTypeConverter

Inherits:
Object
  • Object
show all
Defined in:
lib/arjdbc/jdbc/type_converter.rb

Overview

I want to use JDBC’s DatabaseMetaData#getTypeInfo to choose the best native types to use for ActiveRecord’s Adapter#native_database_types in a database-independent way, but apparently a database driver can return multiple types for a given java.sql.Types constant. So this type converter uses some heuristics to try to pick the best (most common) type to use. It’s not great, it would be better to just delegate to each database’s existin AR adapter’s native_database_types method, but I wanted to try to do this in a way that didn’t pull in all the other adapters as dependencies. Suggestions appreciated.

Constant Summary collapse

AR_TO_JDBC_TYPES =

The basic ActiveRecord types, mapped to an array of procs that are used to #select the best type. The procs are used as selectors in order until there is only one type left. If all the selectors are applied and there is still more than one type, an exception will be raised.

{
  :string      => [ lambda {|r| Jdbc::Types::VARCHAR == r['data_type'].to_i},
                    lambda {|r| r['type_name'] =~ /^varchar/i},
                    lambda {|r| r['type_name'] =~ /^varchar$/i},
                    lambda {|r| r['type_name'] =~ /varying/i}],
  :text        => [ lambda {|r| [Jdbc::Types::LONGVARCHAR, Jdbc::Types::CLOB].include?(r['data_type'].to_i)},
                    lambda {|r| r['type_name'] =~ /^text$/i},     # For Informix
                    lambda {|r| r['type_name'] =~ /sub_type 1$/i}, # For FireBird
                    lambda {|r| r['type_name'] =~ /^(text|clob)$/i},
                    lambda {|r| r['type_name'] =~ /^character large object$/i},
                    lambda {|r| r['sql_data_type'] == 2005}],
  :integer     => [ lambda {|r| Jdbc::Types::INTEGER == r['data_type'].to_i},
                    lambda {|r| r['type_name'] =~ /^integer$/i},
                    lambda {|r| r['type_name'] =~ /^int4$/i},
                    lambda {|r| r['type_name'] =~ /^int$/i}],
  :decimal     => [ lambda {|r| Jdbc::Types::DECIMAL == r['data_type'].to_i},
                    lambda {|r| r['type_name'] =~ /^decimal$/i},
                    lambda {|r| r['type_name'] =~ /^numeric$/i},
                    lambda {|r| r['type_name'] =~ /^number$/i},
                    lambda {|r| r['type_name'] =~ /^real$/i},
                    lambda {|r| r['precision'] == '38'},
                    lambda {|r| r['data_type'].to_i == Jdbc::Types::DECIMAL}],
  :float       => [ lambda {|r| [Jdbc::Types::FLOAT,Jdbc::Types::DOUBLE, Jdbc::Types::REAL].include?(r['data_type'].to_i)},
                    lambda {|r| r['data_type'].to_i == Jdbc::Types::REAL}, #Prefer REAL to DOUBLE for Postgresql
                    lambda {|r| r['type_name'] =~ /^float/i},
                    lambda {|r| r['type_name'] =~ /^double$/i},
                    lambda {|r| r['type_name'] =~ /^real$/i},
                    lambda {|r| r['precision'] == '15'}],
  :datetime    => [ lambda {|r| Jdbc::Types::TIMESTAMP == r['data_type'].to_i},
                    lambda {|r| r['type_name'] =~ /^datetime$/i},
                    lambda {|r| r['type_name'] =~ /^timestamp$/i},
                    lambda {|r| r['type_name'] =~ /^date/i},
                    lambda {|r| r['type_name'] =~ /^integer/i}],  #Num of milliseconds for SQLite3 JDBC Driver
  :timestamp   => [ lambda {|r| Jdbc::Types::TIMESTAMP == r['data_type'].to_i},
                    lambda {|r| r['type_name'] =~ /^timestamp$/i},
                    lambda {|r| r['type_name'] =~ /^datetime/i},
                    lambda {|r| r['type_name'] =~ /^date/i},
                    lambda {|r| r['type_name'] =~ /^integer/i}],  #Num of milliseconds for SQLite3 JDBC Driver
  :time        => [ lambda {|r| Jdbc::Types::TIME == r['data_type'].to_i},
                    lambda {|r| r['type_name'] =~ /^time$/i},
                    lambda {|r| r['type_name'] =~ /^datetime/i},  # For Informix
                    lambda {|r| r['type_name'] =~ /^date/i},
                    lambda {|r| r['type_name'] =~ /^integer/i}],  #Num of milliseconds for SQLite3 JDBC Driver
  :date        => [ lambda {|r| Jdbc::Types::DATE == r['data_type'].to_i},
                    lambda {|r| r['type_name'] =~ /^date$/i},
                    lambda {|r| r['type_name'] =~ /^date/i},
                    lambda {|r| r['type_name'] =~ /^integer/i}],  #Num of milliseconds for SQLite3 JDBC Driver3
  :binary      => [ lambda {|r| [Jdbc::Types::LONGVARBINARY,Jdbc::Types::BINARY,Jdbc::Types::BLOB].include?(r['data_type'].to_i)},
                    lambda {|r| r['type_name'] =~ /^blob/i},
                    lambda {|r| r['type_name'] =~ /sub_type 0$/i}, # For FireBird
                    lambda {|r| r['type_name'] =~ /^varbinary$/i}, # We want this sucker for Mimer
                    lambda {|r| r['type_name'] =~ /^binary$/i}, ],
  :boolean     => [ lambda {|r| [Jdbc::Types::TINYINT].include?(r['data_type'].to_i)},
                    lambda {|r| r['type_name'] =~ /^bool/i},
                    lambda {|r| r['data_type'].to_i == Jdbc::Types::BIT},
                    lambda {|r| r['type_name'] =~ /^tinyint$/i},
                    lambda {|r| r['type_name'] =~ /^decimal$/i},
                    lambda {|r| r['type_name'] =~ /^integer$/i}]
}

Instance Method Summary collapse

Constructor Details

#initialize(types) ⇒ JdbcTypeConverter

Returns a new instance of JdbcTypeConverter.



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# File 'lib/arjdbc/jdbc/type_converter.rb', line 76

def initialize(types)
  @types = types
  @types.each {|t| t['type_name'] ||= t['local_type_name']} # Sybase driver seems to want 'local_type_name'
end

Instance Method Details

#choose_best_types ⇒ Object 



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# File 'lib/arjdbc/jdbc/type_converter.rb', line 81

def choose_best_types
  type_map = {}
  @types.each do |row|
    name = row['type_name'].downcase
    k = name.to_sym
    type_map[k] = { :name => name }
    set_limit_to_nonzero_precision(type_map[k], row)
  end

  AR_TO_JDBC_TYPES.keys.each do |k|
    typerow = choose_type(k)
    type_map[k] = { :name => typerow['type_name'].downcase }
    case k
    when :integer, :string, :decimal
      set_limit_to_nonzero_precision(type_map[k], typerow)
    when :boolean
      type_map[k][:limit] = 1
    end
  end
  type_map
end

#choose_type(ar_type) ⇒ Object 



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# File 'lib/arjdbc/jdbc/type_converter.rb', line 103

def choose_type(ar_type)
  procs = AR_TO_JDBC_TYPES[ar_type]
  types = @types
  procs.each do |p|
    new_types = types.reject {|r| r["data_type"].to_i == Jdbc::Types::OTHER}
    new_types = new_types.select(&p)
    new_types = new_types.inject([]) do |typs,t|
      typs << t unless typs.detect {|el| el['type_name'] == t['type_name']}
      typs
    end
    return new_types.first if new_types.length == 1
    types = new_types if new_types.length > 0
  end
  raise "unable to choose type for #{ar_type} from:\n#{types.collect{|t| t['type_name']}.inspect}"
end

#set_limit_to_nonzero_precision(map, row) ⇒ Object 



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# File 'lib/arjdbc/jdbc/type_converter.rb', line 119

def set_limit_to_nonzero_precision(map, row)
  if row['precision'] && row['precision'].to_i > 0
    map[:limit] = row['precision'].to_i
  end
end