Class: Innodb::RecordDescriber

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

Overview

A class to describe record layouts for InnoDB indexes. Designed to be usable in two different ways: statically built and dynamically built. Note that in both cases, the order that statements are encountered is critical. Columns must be added to the key and row structures in the correct order.

STATIC USAGE

Static building is useful for building a custom describer for any index and looks like the following:

To describe the SQL syntax:

CREATE TABLE my_table (
  id BIGINT NOT NULL,
  name VARCHAR(100) NOT NULL,
  age INT UNSIGNED,
  PRIMARY KEY (id)
);

The clustered key would require a class like:

class MyTableClusteredDescriber < Innodb::RecordDescriber
  type :clustered
  key "id", :BIGINT, :UNSIGNED, :NOT_NULL
  row "name", "VARCHAR(100)", :NOT_NULL
  row "age", :INT, :UNSIGNED
end

It can then be instantiated as usual:

my_table_clustered = MyTableClusteredDescriber.new

All statically-defined type, key, and row information will be copied into the instance when it is initialized. Once initialized, the instance can be additionally used dynamically, as per below. (A dynamic class is just the same as a static class that is empty.)

Note that since InnoDB works in terms of indexes individually, a new class must be created for each index.

DYNAMIC USAGE

If a record describer needs to be built based on runtime information, such as index descriptions from a live data dictionary, instances can be built dynamically. For the same table above, this would require:

my_table_clustered = Innodb::RecordDescriber.new
my_table_clustered.type = :clustered
my_table_clustered.key "id", :BIGINT, :UNSIGNED, :NOT_NULL
my_table_clustered.row "name", "VARCHAR(100)", :NOT_NULL
my_table_clustered.row "age", :INT, :UNSIGNED

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ RecordDescriber

Returns a new instance of RecordDescriber.



89
90
91
 
# File 'lib/innodb/record_describer.rb', line 89

def initialize
  @description = self.class.static_description.dup
end

Instance Attribute Details

#description ⇒ Object

Returns the value of attribute description.



87
88
89
 
# File 'lib/innodb/record_describer.rb', line 87

def description
  @description
end

Class Method Details

.add_static_field(group, name, type) ⇒ Object

An internal method wrapped with ‘key’ and ‘row’ helpers.



73
74
75
 
# File 'lib/innodb/record_describer.rb', line 73

def self.add_static_field(group, name, type)
  static_description[group] << { :name => name, :type => type }
end

.key(name, *type) ⇒ Object

A ‘key’ method to be used from the DSL.



78
79
80
 
# File 'lib/innodb/record_describer.rb', line 78

def self.key(name, *type)
  add_static_field :key, name, type
end

.row(name, *type) ⇒ Object

A ‘row’ method to be used from the DSL.



83
84
85
 
# File 'lib/innodb/record_describer.rb', line 83

def self.row(name, *type)
  add_static_field :row, name, type
end

.static_description ⇒ Object

Internal method to initialize the class’s instance variable on access.



59
60
61
62
63
64
65
 
# File 'lib/innodb/record_describer.rb', line 59

def self.static_description
  @static_description ||= {
    :type => nil,
    :key => [],
    :row => []
  }
end

.type(type) ⇒ Object

A ‘type’ method to be used from the DSL.



68
69
70
 
# File 'lib/innodb/record_describer.rb', line 68

def self.type(type)
  static_description[:type] = type
end

Instance Method Details

#add_field(group, name, type) ⇒ Object

An internal method wrapped with ‘key’ and ‘row’ helpers.



99
100
101
 
# File 'lib/innodb/record_describer.rb', line 99

def add_field(group, name, type)
  description[group] << { :name => name, :type => type }
end

#key(name, *type) ⇒ Object

Add a key column to the record description.



104
105
106
 
# File 'lib/innodb/record_describer.rb', line 104

def key(name, *type)
  add_field :key, name, type
end

#row(name, *type) ⇒ Object

Add a row (non-key) column to the record description.



109
110
111
 
# File 'lib/innodb/record_describer.rb', line 109

def row(name, *type)
  add_field :row, name, type
end

#type(type) ⇒ Object

Set the type of this record (:clustered or :secondary).



94
95
96
 
# File 'lib/innodb/record_describer.rb', line 94

def type(type)
  description[:type] = type
end