Class: Innodb::Field

Inherits:
Object
  • Object
show all
Defined in:
lib/innodb/field.rb

Overview

A single field in an InnoDB record (within an INDEX page). This class provides essential information to parse records, including the length of the fixed-width and variable-width portion of the field.

Constant Summary collapse

EXTERN_FIELD_SIZE =

Size of a reference to data stored externally to the page.

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Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(position, name, type_definition, *properties) ⇒ Field

Returns a new instance of Field.



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# File 'lib/innodb/field.rb', line 14

def initialize(position, name, type_definition, *properties)
  @position = position
  @name = name
  @nullable = properties.delete(:NOT_NULL) ? false : true
  base_type, modifiers = parse_type_definition(type_definition.to_s)
  @data_type = Innodb::DataType.new(base_type, modifiers, properties)
end

Instance Attribute Details

#data_type ⇒ Object (readonly)

Returns the value of attribute data_type.



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# File 'lib/innodb/field.rb', line 9

def data_type
  @data_type
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/innodb/field.rb', line 9

def name
  @name
end

#nullable ⇒ Object (readonly)

Returns the value of attribute nullable.



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# File 'lib/innodb/field.rb', line 9

def nullable
  @nullable
end

#position ⇒ Object (readonly)

Returns the value of attribute position.



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# File 'lib/innodb/field.rb', line 9

def position
  @position
end

Instance Method Details

#blob? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/innodb/field.rb', line 43

def blob?
  @data_type.is_a? Innodb::DataType::BlobType
end

#extern(record, cursor) ⇒ Object

Read an InnoDB external pointer field.



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# File 'lib/innodb/field.rb', line 70

def extern(record, cursor)
  return nil if not extern?(record)
  cursor.name(@name) { read_extern(cursor) }
end

#extern?(record) ⇒ Boolean

Return whether a part of this field is stored externally (off-page).

Returns:

  • (Boolean) 


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# File 'lib/innodb/field.rb', line 33

def extern?(record)
  record[:header][:field_externs][position]
end

#length(record) ⇒ Object

Return the actual length of this variable-length field.



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# File 'lib/innodb/field.rb', line 48

def length(record)
  if variable?
    len = record[:header][:field_lengths][position]
  else
    len = @data_type.width
  end
  extern?(record) ? len - EXTERN_FIELD_SIZE : len
end

#null?(record) ⇒ Boolean

Return whether this field is NULL.

Returns:

  • (Boolean) 


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# File 'lib/innodb/field.rb', line 28

def null?(record)
  nullable? && record[:header][:field_nulls][position]
end

#nullable? ⇒ Boolean

Return whether this field can be NULL.

Returns:

  • (Boolean) 


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# File 'lib/innodb/field.rb', line 23

def nullable?
  @nullable
end

#read(record, cursor) ⇒ Object

Read an InnoDB encoded data field.



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# File 'lib/innodb/field.rb', line 58

def read(record, cursor)
  cursor.name(@data_type.name) { cursor.get_bytes(length(record)) }
end

#value(record, cursor) ⇒ Object

Read the data value (e.g. encoded in the data).



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# File 'lib/innodb/field.rb', line 63

def value(record, cursor)
  return :NULL if null?(record)
  data = read(record, cursor)
  @data_type.respond_to?(:value) ? @data_type.value(data) : data
end

#variable? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/innodb/field.rb', line 37

def variable?
  @data_type.is_a? Innodb::DataType::BlobType or
  @data_type.is_a? Innodb::DataType::VariableBinaryType or
  @data_type.is_a? Innodb::DataType::VariableCharacterType
end