Class: DatastaxRails::Base

Inherits:
Object show all
Extended by:
ActiveSupport::DescendantsTracker
Includes:
ActiveModel::Model, Associations, AttributeAssignment, AttributeMethods, AutosaveAssociation, Batches, Callbacks, Connection, FinderMethods, Inheritance, Persistence, Reflection, Scoping, Serialization, SolrRepair, Timestamps, Validations
Defined in:
lib/datastax_rails/base.rb

Overview

DatastaxRails

DatastaxRails-based objects differ from Active Record objects in that they specify their attributes directly on the model. This is necessary because of the fact that Cassandra column families do not have a set list of columns but rather can have different columns per row. (This is not strictly true any more, but it’s still not as nailed down as SQL.) By specifying the attributes on the model, getters and setters are automatically created, and the attribute is automatically indexed into SOLR.

Primary Keys

Several types of primary keys are supported in DSR. The most common type used is UUID. In general, incrementing numbers are not used as there is no way to guarantee a consistent one-up number across nodes. The following will cause a unique UUID to be generated for each model. This works best if you are using the RandomPartitioner in your Datastax cluster.

class Person < DatastaxRails::Base
  uuid :id
end

You don’t have to use a uuid. You can use a different column as your primary key.

class Person < DatastaxRails::Base
  self.primary_key = 'userid'
  string :userid
end

Attributes

Attributes are specified near the top of the model. The following attribute types are supported:

  • binary - a large object that will not be indexed into SOLR (e.g., BLOB)

  • boolean - true/false values

  • date - a date without a time component

  • double - a 64-bit number in floating point notation

  • float - a 32-bit number in floating point notation

  • integer - a 32-bit signed integer

  • list - an ordered list of values of a single type

  • long - a 64-bit signed integer

  • map - a collection of key/value pairs of a single type (keys are always strings)

  • set - an un-ordered set of unique values of a single type

  • string - a generic string type that is not tokenized by default

  • text - like strings but will be tokenized for full-text searching by default

  • time - a datetime object

  • timestamps - a special type that instructs DSR to include created_at and updated_at

  • uuid - a UUID in standard UUID format

The following options may be specified on the various types to control how they are indexed into SOLR:

  • solr_index - If the attribute should the attribute be indexed into SOLR. Defaults to true for everything but binary.

  • solr_store - If the attribute should the attribute be stored in SOLR. Defaults to true for everything but binary. (see note)

  • sortable - If the attribute should be sortable by SOLR. Defaults to true for everything but binary and text. (see note)

  • tokenized - If the attribute should be tokenized for full-text searching within the field. Defaults to true for text.

  • fulltext - If the attribute should be included in the default field for full-text searches. Defaults to true for text and string.

  • multi_valued - If the field will contain multiple values in Solr. Defaults to true for list and set. This should never need to be set manually.

NOTES:

  • No fields are actually stored in SOLR. When a field is requested from SOLR, the field is retrieved from Cassandra behind the scenes and returned as if it were stored. The stored parameter actually controls whether SOLR will return the field at all. If a field is not stored then asking SOLR for it will return a nil value. It will also not be included in the field list when all (*) fields are requested.

  • If you want a field both sortable and searchable (e.g., a subject) then declare it a text field with :sortable => true. This will create two copies of the field in SOLR, one that gets tokenized and one that is a single token for sorting. As this inflates the size of the index, you don’t want to do this for large fields (which probably don’t make sense to sort on anyways).

EXAMPLE:

class Person < DatastaxRails::Base
  uuid    :id
  string  :first_name
  string  :user_name
  text    :bio
  date    :birthdate
  boolean :active
  timestamps
end

Schemas

DSR will automatically manage both the Cassandra and Solr schemas for you based on the attributes that you specify on the model. You can override the Solr schema if you want to have something custom. There is a rake task that manages all of the schema information. It will create column families and columns as needed and upload the Solr schema when necessary. If there are changes, it will automatically kick off a reindex in the background.

As of Cassandra 1.2, there is no way to remove a column. Cassandra 2.0 supports it, but it hasn’t been implemented in DSR yet.

TODO: Need a way to remove ununsed column families.

Creation

DatastaxRails objects accept constructor parameters either in a hash or as a block. The hash method is especially useful when you’re receiving the data from somewhere else, like an HTTP request. It works like this:

user = User.new(name: "David", occupation: "Code Artist")
user.name # => "David"

You can also use block initialization:

user = User.new do |u|
  u.name = "David"
  u.occupation = "Code Artist"
end

And of course you can just create a bare object and specify the attributes after the fact:

user = User.new
user.name = "David"
user.occupation = "Code Artist"

Consistency

Cassandra has a concept of consistency levels when it comes to saving records. For a detailed discussion on Cassandra data consistency, see: www.datastax.com/documentation/cassandra/1.2/cassandra/dml/dml_config_consistency_c.html

DatastaxRails allows you to specify the consistency when you save and retrieve objects.

user = User.new(name: 'David')
user.save(consistency: 'ALL')

User.create(params[:user], {consistency: :local_quorum})

User.consistency(:local_quorum).where(name: 'David')

The default consistency level in DatastaxRails is QUORUM for writes and for retrieval by ID. SOLR only supports a consistency level of ONE. See the documentation for SearchMethods#consistency for a more detailed explanation.

The overall default consistency for a given model can be overridden by setting the default_consistency property.

class Model < DatastaxRails::Base
  self.default_consistency = :local_quorum
end

The default consistency for all models can be selected by setting the property on DatastaxRails::Base.

DatastaxRails::Base.default_consistency = :one

Conditions

Conditions are specified as a hash representing key/value pairs that will eventually be passed to SOLR or as a chained call for greater_than and less_than conditions. In addition, fulltext queries may be specified as a string that will eventually be parsed by SOLR as a standard SOLR query.

A simple hash without a statement will generate conditions based on equality using boolean AND logic. For instance:

Student.where(first_name: "Harvey", status: 1)
Student.where(params[:student])

A range may be used in the hash to use a SOLR range query:

Student.where(grade: 9..12)

An array may be used in the hash to construct a SOLR OR query:

Student.where(grade: [9,11,12])

Inequality can be tested for like so:

Student.where_not(grade: 9)
Student.where(:grade).greater_than(9)
Student.where(:grade).less_than(10)

NOTE that Solr inequalities are inclusive so really, the second example above is retrieving records where grace is greater than or equal to 9. Be sure to keep this in mind when you do inequality queries.

Fulltext searching is natively supported. All string and text fields are automatically indexed for fulltext searching.

Post.fulltext('Apple AND "iPhone 4s"')

See the documentation on SearchMethods for more information and examples.

Overwriting default accessors

All column values are automatically available through basic accessors on the object, but sometimes you want to specialize this behavior. This can be done by overwriting the default accessors (using the same name as the attribute) and calling read_attribute(attr_name) and write_attribute(attr_name, value) to actually change things.

class Song < DatastaxRails::Base
  # Uses an integer of seconds to hold the length of the song

  def length=(minutes)
    write_attribute(:length, minutes.to_i * 60)
  end

  def length
    read_attribute(:length) / 60
  end
end

You can alternatively use self[:attribute]=(value) and self[:attribute] instead of write_attribute(:attribute, value) and read_attribute(:attribute).

Dynamic attribute-based finders

Dynamic finders have been removed from Rails. As a result, they have also been removed from DSR. In its place, the find_by method can be used:

Student.find_by(name: 'Jason')

NOTE: there is a subtle difference between the following that does not exist in ActiveRecord:

Student.find_by(name: 'Jason')
Student.where(name: 'Jason').first

The difference is that the first is escaped so that special characters can be used. The second method requires you to do the escaping yourself if you need it done. As an example,

Company.find_by(name: 'All*') #=> finds only the company with the literal name 'All*'
Company.where(name: 'All*').first #=> finds the first company whose name begins with All

See DatastaxRails::FinderMethods for more information

Facets

DSR support both field and range facets. For additional detail on facets, see the documentation available under the FacetMethods module. The result is available through the facets accessor.

results = Article.field_facet(:author)
results.facets #=> {"author"=>["vonnegut", 2. "asimov", 3]}

Model.field_facet(:author)
Model.field_facet(:author, sort: 'count', limit: 10, mincount: 1)
Model.range_facet(:price, 500, 1000, 10)
Model.range_facet(:price, 500, 1000, 10, include: 'all')
Model.range_facet(:publication_date, "1968-01-01T00:00:00Z", "2000-01-01T00:00:00Z", "+1YEAR")

Range Gap syntax for dates: 1YEAR, 5YEAR, 5YEARS, 1MONTH, +1DAY

Useful constants:

DatastaxRails::FacetMethods::BY_YEAR (+1YEAR) DatastaxRails::FacetMethods::BY_MONTH (+1MONTH) DatastaxRails::FacetMethods::BY_DAY (+1DAY)

Model.range_facet(:publication_date,

"1968-01-01T00:00:00Z",
"2000-01-01T00:00:00Z",
DatastaxRails::FacetMethods::BY_YEAR)

Collections

Cassandra supports the notion of collections on a row. The three types of supported collections are set, list, and map.

By default collections hold strings. You can override this by passing a :holds option in the attribute definition. Sets can hold anything other than other collections, however, a given collection can only hold a single type of values.

NOTE: There is a limitation in Cassandra where only the first 64k entries of a collection are ever returned with a query. Therefore, if you put more than 64k entries in a collection you will lose data.

Set

A set is an un-ordered collection of unique values. This collection is fully searchable in Solr.

class User < DatastaxRails::Base
  uuid   :id
  string :username
  set    :emails
end

The default set will hold strings. You can modify this behavior like so:

class Student < DatastaxRails::Base
  uuid   :id
  string :name
  set    :grades, holds: :integers
end

User.where(emails: '[email protected]') #=> Returns all users where [email protected] is in the set
user = User.new(name: 'Jim', emails: ['[email protected]'])
user.emails << '[email protected]'
user.emails #=> ['[email protected]']

List

An ordered collection of values. They do not necessarily have to be unique. The collection will be fully searchable in Solr.

class Student < DatastaxRails::Base
  uuid :id
  string :name
  list :classrooms, holds: integers
end

Student.where(classrooms: 307) #=> Returns all students that have a class in room 307.
student = Student.new(name: 'Sally', classrooms: [307, 305, 301, 307])
student.classrooms << 304
student.classrooms #=> [307, 305, 301, 307, 304]

Map

A collection of key/value pairs where the key is a string and the value is the specified type. The collection becomes available in Solr as dynamic fields.

class Student < DatastaxRails::Base
  uuid :id
  string :name
  map :scores_, holds: :integers
end

student = Student.new(:name 'Sally')
student.scores['midterm'] = 98
student.scores['final'] = 97
student.scores #=> {'scores_midterm' => 98, 'scores_final' => 97}
Student.where(scores_final: 97) #=> Returns all students that scored 97 on their final

Note that the map name gets prepended to the key. This is how Solr maps it’s dynamic fields into the cassandra map. For this reason, it’s usually a good idea to put an underscore (_) at the end of the map name to prevent collisions.

Exceptions

  • DatastaxRailsError - Generic error class and superclass of all other errors raised by DatastaxRails.

  • AssociationTypeMismatch - The object assigned to the association wasn’t of the type specified in the association definition.

  • ConnectionNotEstablished+ - No connection has been established. Use establish_connection before querying.

  • RecordNotFound - No record responded to the find method. Either the row with the given ID doesn’t exist or the row didn’t meet the additional restrictions. Some find calls do not raise this exception to signal nothing was found, please check its documentation for further details.

  • UnknownAttributeError - The specified attribute isn’t defined on your model.

See the documentation for SearchMethods for more examples of using the search API.

Direct Known Subclasses

WideStorageModel

Constant Summary

Constants included from Callbacks

Callbacks::CALLBACKS

Class Attribute Summary collapse

Instance Attribute Summary collapse

Attributes included from AutosaveAssociation

#destroyed_by_association, #marked_for_destruction

Attributes included from Associations

#association_cache

Class Method Summary collapse

Instance Method Summary collapse

Methods included from SolrRepair

#repair_solr

Methods included from Serialization

#serializable_hash, #to_xml

Methods included from Timestamps

#initialize_dup

Methods included from AutosaveAssociation

#changed_for_autosave?, #mark_for_destruction, #reload

Methods included from Associations

#association, #clear_association_cache

Methods included from Callbacks

#destroy

Methods included from Validations

#save, #save!, #valid?

Methods included from AttributeMethods

#attribute_exists?, #attribute_for_inspect, #column_for_attribute, #method_missing, #respond_to?

Methods included from AttributeAssignment

#assign_attributes

Methods included from Batches

#find_each, #find_each_with_index, #find_in_batches

Methods included from FinderMethods

#find, #find_by, #find_by!, #first, #first!, #last, #last!

Methods included from Persistence

#destroy, #persisted?, #reload, #save, #save!, #toggle, #toggle!, #update_attribute, #update_attributes, #update_attributes!

Constructor Details

#initialize(attributes = {}, _options = {}) {|_self| ... } ⇒ Base

Returns a new instance of Base.

Yields:

  • (_self)

Yield Parameters:



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# File 'lib/datastax_rails/base.rb', line 436

def initialize(attributes = {}, _options = {})
  defaults = self.class.column_defaults.dup
  defaults.each { |_k, v| v.duplicable? ? v.dup : v }

  @attributes = initialize_attributes(defaults)
  @column_types = self.class.columns_hash

  init_internals
  init_changed_attributes
  populate_with_current_scope_attributes

  assign_attributes(attributes) if attributes

  yield self if block_given?
  run_callbacks :initialize unless _initialize_callbacks.empty?
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method in the class DatastaxRails::AttributeMethods

Class Attribute Details

.column_family ⇒ Object

Returns the column family name. If it has been set manually, the set name is returned. Otherwise returns the pluralized version of the class name.

Returns [String] the name of the column family



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# File 'lib/datastax_rails/base.rb', line 588

def column_family
  @column_family || name.underscore.pluralize
end

Instance Attribute Details

#attributes ⇒ Object (readonly)

Returns the value of attribute attributes.



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# File 'lib/datastax_rails/base.rb', line 427

def attributes
  @attributes
end

#key ⇒ Object

Returns the value of attribute key.



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# File 'lib/datastax_rails/base.rb', line 429

def key
  @key
end

#loaded_attributes ⇒ Object (readonly)

Returns the value of attribute loaded_attributes.



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# File 'lib/datastax_rails/base.rb', line 428

def loaded_attributes
  @loaded_attributes
end

Class Method Details

.attribute_names ⇒ Object Also known as: column_names

Returns an array of attribute names as strings



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# File 'lib/datastax_rails/base.rb', line 621

def attribute_names
  @attribute_names ||= attribute_definitions.keys.map(&:to_s)
end

.base_class ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 604

def base_class
  klass = self
  klass = klass.superclass while klass.superclass != Base
  klass
end

.columns ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 626

def columns
  @columns ||= attribute_definitions.values
end

.default_page_size ⇒ Object

SOLR always paginates all requests. There is no way to disable it, so we are setting the default page size to an arbitrarily high number so that we effectively remove pagination. If you instead want a model set to something more sane, then override this method in your model and set it. Of course, the page size can always be raised or lowered for an individual request.

class Model < DatastaxRails::Base
  def self.default_page_size
    30
  end
end



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# File 'lib/datastax_rails/base.rb', line 641

def default_page_size
  100_000
end

.find_by_id(id) ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 610

def find_by_id(id)
  scoped.with_cassandra.find(id)
rescue RecordNotFound
  nil
end

.inspect ⇒ Object

Returns a string like ‘Post(id:integer, title:string, body:text)’



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# File 'lib/datastax_rails/base.rb', line 655

def inspect
  if self == Base
    super
  else
    attr_list = columns.map { |c| "#{c.name}: #{c.type}" } * ', '
    "#{super}(#{attr_list})"
  end
end

.logger ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 616

def logger
  Rails.logger
end

.models ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 592

def models
  descendants.reject(&:abstract_class?)
end

.payload_model? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/datastax_rails/base.rb', line 596

def payload_model?
  ancestors.include?(DatastaxRails::PayloadModel)
end

.search_ids(&block) ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 645

def search_ids(&block)
  search = solr_search(&block)
  search.raw_results.map(&:primary_key)
end

.valid_consistency?(level) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/datastax_rails/base.rb', line 650

def valid_consistency?(level) #:nodoc:
  DatastaxRails::Cql::Consistency::VALID_CONSISTENCY_LEVELS.include?(level.to_s.downcase.to_sym)
end

.wide_storage_model? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/datastax_rails/base.rb', line 600

def wide_storage_model?
  ancestors.include?(DatastaxRails::WideStorageModel)
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 538

def ==(other)
  super ||
    other.instance_of?(self.class) &&
      id.present? &&
      other.id.eql?(id)
end

#attribute_names ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 549

def attribute_names
  self.class.attribute_names
end

#column_names ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 552

def attribute_names
  self.class.attribute_names
end

#eql?(other) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/datastax_rails/base.rb', line 545

def eql?(other)
  self == (other)
end

#freeze ⇒ Object

Freeze the attributes hash such that associations are still accessible, even on destroyed records.



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# File 'lib/datastax_rails/base.rb', line 504

def freeze
  @attributes.freeze
  self
end

#frozen? ⇒ Boolean

Returns true if the attributes hash has been frozen.

Returns:

  • (Boolean) 


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# File 'lib/datastax_rails/base.rb', line 510

def frozen?
  @attributes.frozen?
end

#hash ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 534

def hash
  id.hash
end

#init_changed_attributes ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 494

def init_changed_attributes
  # Intentionally avoid using #column_defaults since overridden defaults
  # won't get written unless they get marked as changed
  self.class.columns.each do |c|
    attr, orig_value = c.name, c.empty_value
    @changed_attributes[attr] = nil if _field_changed?(attr, orig_value, @attributes[attr.to_s])
  end
end

#init_internals ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 478

def init_internals
  pk = self.class.primary_key
  @attributes[pk] = nil unless @attributes.key?(pk)

  @association_cache = {}
  @attributes_cache = {}
  @previously_changed = {}.with_indifferent_access
  @changed_attributes = {}.with_indifferent_access
  @loaded_attributes = Hash[@attributes.map { |k, _v| [k, true] }].with_indifferent_access
  @readonly = false
  @destroyed = false
  @marked_for_destruction = false
  @destroyed_by_association = nil
  @new_record = true
end

#init_with(coder) ⇒ Object

Initialize an empty model object from coder. coder must contain the attributes necessary for initializing an empty model object. For example:

class Post < DatastaxRails::Base
end

post = Post.allocate
post.init_with('attributes' => { 'title' => 'hello world' })
post.title # => 'hello world'



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# File 'lib/datastax_rails/base.rb', line 463

def init_with(coder)
  Types::DirtyCollection.ignore_modifications do
    @attributes   = initialize_attributes(coder['attributes'])
    @column_types_override = coder['column_types']
    @column_types = self.class.columns_hash

    init_internals

    @new_record = false
    run_callbacks :find
    run_callbacks :initialize
  end
  self
end

#inspect ⇒ Object

Returns the contents of the record as a nicely formatted string.



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# File 'lib/datastax_rails/base.rb', line 515

def inspect
  # We check defined?(@attributes) not to issue warnings if the object is
  # allocated but not initialized.
  inspection = if defined?(@attributes) && @attributes
                 self.class.column_names.map do |name|
                   if has_attribute?(name)
                     "#{name}: #{attribute_for_inspect(name)}"
                   end
                 end.compact.join(', ')
               else
                 'not initialized'
               end
  "#<#{self.class} #{inspection}>"
end

#to_param ⇒ Object 



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# File 'lib/datastax_rails/base.rb', line 530

def to_param
  id.to_s if persisted?
end

#valid_consistency?(level) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean) 


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# File 'lib/datastax_rails/base.rb', line 554

def valid_consistency?(level) #:nodoc:
  self.class.valid_consistency?(level)
end