module Sequel::Model::Associations::DatasetMethods

Eager loading makes it so that you can load all associated records for a set of objects in a single query, instead of a separate query for each object.

Two separate implementations are provided. eager should be used most of the time, as it loads associated records using one query per association. However, it does not allow you the ability to filter or order based on columns in associated tables. eager_graph loads all records in a single query using JOINs, allowing you to filter or order based on columns in associated tables. However, eager_graph is usually slower than eager, especially if multiple one_to_many or many_to_many associations are joined.

You can cascade the eager loading (loading associations on associated objects) with no limit to the depth of the cascades. You do this by passing a hash to eager or eager_graph with the keys being associations of the current model and values being associations of the model associated with the current model via the key.

The arguments can be symbols or hashes with symbol keys (for cascaded eager loading). Examples:

Album.eager(:artist).all
Album.eager_graph(:artist).all
Album.eager(:artist, :genre).all
Album.eager_graph(:artist, :genre).all
Album.eager(:artist).eager(:genre).all
Album.eager_graph(:artist).eager_graph(:genre).all
Artist.eager(albums: :tracks).all
Artist.eager_graph(albums: :tracks).all
Artist.eager(albums: {tracks: :genre}).all
Artist.eager_graph(albums: {tracks: :genre}).all

You can also pass a callback as a hash value in order to customize the dataset being eager loaded at query time, analogous to the way the :eager_block association option allows you to customize it at association definition time. For example, if you wanted artists with their albums since 1990:

Artist.eager(albums: proc{|ds| ds.where{year > 1990}})

Or if you needed albums and their artist's name only, using a single query:

Albums.eager_graph(artist: proc{|ds| ds.select(:name)})

To cascade eager loading while using a callback, you substitute the cascaded associations with a single entry hash that has the proc callback as the key and the cascaded associations as the value. This will load artists with their albums since 1990, and also the tracks on those albums and the genre for those tracks:

Artist.eager(albums: {proc{|ds| ds.where{year > 1990}}=>{tracks: :genre}})

Public Instance Methods

as_hash(key_column=nil, value_column=nil, opts=OPTS) click to toggle source

If the dataset is being eagerly loaded, default to calling all instead of each.

Calls superclass method
     # File lib/sequel/model/associations.rb
3134 def as_hash(key_column=nil, value_column=nil, opts=OPTS)
3135   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3136     opts = Hash[opts]
3137     opts[:all] = true
3138   end
3139   super
3140 end
association_join(*associations) click to toggle source

Adds one or more INNER JOINs to the existing dataset using the keys and conditions specified by the given association(s). Take the same arguments as eager_graph, and operates similarly, but only adds the joins as opposed to making the other changes (such as adding selected columns and setting up eager loading).

The following methods also exist for specifying a different type of JOIN:

association_full_join

FULL JOIN

association_inner_join

INNER JOIN

association_left_join

LEFT JOIN

association_right_join

RIGHT JOIN

Examples:

# For each album, association_join load the artist
Album.association_join(:artist).all
# SELECT *
# FROM albums
# INNER JOIN artists AS artist ON (artists.id = albums.artist_id)

# For each album, association_join load the artist, using a specified alias
Album.association_join(Sequel[:artist].as(:a)).all
# SELECT *
# FROM albums
# INNER JOIN artists AS a ON (a.id = albums.artist_id)

# For each album, association_join load the artist and genre
Album.association_join(:artist, :genre).all
Album.association_join(:artist).association_join(:genre).all
# SELECT *
# FROM albums
# INNER JOIN artists AS artist ON (artist.id = albums.artist_id)
# INNER JOIN genres AS genre ON (genre.id = albums.genre_id)

# For each artist, association_join load albums and tracks for each album
Artist.association_join(albums: :tracks).all
# SELECT *
# FROM artists
# INNER JOIN albums ON (albums.artist_id = artists.id)
# INNER JOIN tracks ON (tracks.album_id = albums.id)

# For each artist, association_join load albums, tracks for each album, and genre for each track
Artist.association_join(albums: {tracks: :genre}).all
# SELECT *
# FROM artists
# INNER JOIN albums ON (albums.artist_id = artists.id)
# INNER JOIN tracks ON (tracks.album_id = albums.id)
# INNER JOIN genres AS genre ON (genre.id = tracks.genre_id)

# For each artist, association_join load albums with year > 1990
Artist.association_join(albums: proc{|ds| ds.where{year > 1990}}).all
# SELECT *
# FROM artists
# INNER JOIN (
#   SELECT * FROM albums WHERE (year > 1990)
# ) AS albums ON (albums.artist_id = artists.id)

# For each artist, association_join load albums and tracks 1-10 for each album
Artist.association_join(albums: {tracks: proc{|ds| ds.where(number: 1..10)}}).all
# SELECT *
# FROM artists
# INNER JOIN albums ON (albums.artist_id = artists.id)
# INNER JOIN (
#   SELECT * FROM tracks WHERE ((number >= 1) AND (number <= 10))
# ) AS tracks ON (tracks.albums_id = albums.id)

# For each artist, association_join load albums with year > 1990, and tracks for those albums
Artist.association_join(albums: {proc{|ds| ds.where{year > 1990}}=>:tracks}).all
# SELECT *
# FROM artists
# INNER JOIN (
#   SELECT * FROM albums WHERE (year > 1990)
# ) AS albums ON (albums.artist_id = artists.id)
# INNER JOIN tracks ON (tracks.album_id = albums.id)
     # File lib/sequel/model/associations.rb
2844 def association_join(*associations)
2845   association_inner_join(*associations)
2846 end
complex_expression_sql_append(sql, op, args) click to toggle source

If the expression is in the form x = y where y is a Sequel::Model instance, array of Sequel::Model instances, or a Sequel::Model dataset, assume x is an association symbol and look up the association reflection via the dataset's model. From there, return the appropriate SQL based on the type of association and the values of the foreign/primary keys of y. For most association types, this is a simple transformation, but for many_to_many associations this creates a subquery to the join table.

Calls superclass method
     # File lib/sequel/model/associations.rb
2855 def complex_expression_sql_append(sql, op, args)
2856   r = args[1]
2857   if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) ||
2858       (multiple = ((op == :IN || op == :'NOT IN') && ((is_ds = r.is_a?(Sequel::Dataset)) || (r.respond_to?(:all?) && r.all?{|x| x.is_a?(Sequel::Model)})))))
2859     l = args[0]
2860     if ar = model.association_reflections[l]
2861       if multiple
2862         klass = ar.associated_class
2863         if is_ds
2864           if r.respond_to?(:model)
2865             unless r.model <= klass
2866               # A dataset for a different model class, could be a valid regular query
2867               return super
2868             end
2869           else
2870             # Not a model dataset, could be a valid regular query
2871             return super
2872           end
2873         else
2874           unless r.all?{|x| x.is_a?(klass)}
2875             raise Sequel::Error, "invalid association class for one object for association #{l.inspect} used in dataset filter for model #{model.inspect}, expected class #{klass.inspect}"
2876           end
2877         end
2878       elsif !r.is_a?(ar.associated_class)
2879         raise Sequel::Error, "invalid association class #{r.class.inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}, expected class #{ar.associated_class.inspect}"
2880       end
2881 
2882       if exp = association_filter_expression(op, ar, r)
2883         literal_append(sql, exp)
2884       else
2885         raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}"
2886       end
2887     elsif multiple && (is_ds || r.empty?)
2888       # Not a query designed for this support, could be a valid regular query
2889       super
2890     else
2891       raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}"
2892     end
2893   else
2894     super
2895   end
2896 end
eager(*associations) click to toggle source

The preferred eager loading method. Loads all associated records using one query for each association.

The basic idea for how it works is that the dataset is first loaded normally. Then it goes through all associations that have been specified via eager. It loads each of those associations separately, then associates them back to the original dataset via primary/foreign keys. Due to the necessity of all objects being present, you need to use all to use eager loading, as it can't work with each.

This implementation avoids the complexity of extracting an object graph out of a single dataset, by building the object graph out of multiple datasets, one for each association. By using a separate dataset for each association, it avoids problems such as aliasing conflicts and creating cartesian product result sets if multiple one_to_many or many_to_many eager associations are requested.

One limitation of using this method is that you cannot filter the current dataset based on values of columns in an associated table, since the associations are loaded in separate queries. To do that you need to load all associations in the same query, and extract an object graph from the results of that query. If you need to filter based on columns in associated tables, look at eager_graph or join the tables you need to filter on manually.

Each association's order, if defined, is respected. If the association uses a block or has an :eager_block argument, it is used.

To modify the associated dataset that will be used for the eager load, you should use a hash for the association, with the key being the association name symbol, and the value being a callable object that is called with the associated dataset and should return a modified dataset. If that association also has dependent associations, instead of a callable object, use a hash with the callable object being the key, and the dependent association(s) as the value.

Examples:

# For each album, eager load the artist
Album.eager(:artist).all
# SELECT * FROM albums
# SELECT * FROM artists WHERE (id IN (...))

# For each album, eager load the artist and genre
Album.eager(:artist, :genre).all
Album.eager(:artist).eager(:genre).all
# SELECT * FROM albums
# SELECT * FROM artists WHERE (id IN (...))
# SELECT * FROM genres WHERE (id IN (...))

# For each artist, eager load albums and tracks for each album
Artist.eager(albums: :tracks).all
# SELECT * FROM artists
# SELECT * FROM albums WHERE (artist_id IN (...))
# SELECT * FROM tracks WHERE (album_id IN (...))

# For each artist, eager load albums, tracks for each album, and genre for each track
Artist.eager(albums: {tracks: :genre}).all
# SELECT * FROM artists
# SELECT * FROM albums WHERE (artist_id IN (...))
# SELECT * FROM tracks WHERE (album_id IN (...))
# SELECT * FROM genre WHERE (id IN (...))

# For each artist, eager load albums with year > 1990
Artist.eager(albums: proc{|ds| ds.where{year > 1990}}).all
# SELECT * FROM artists
# SELECT * FROM albums WHERE ((year > 1990) AND (artist_id IN (...)))

# For each artist, eager load albums and tracks 1-10 for each album
Artist.eager(albums: {tracks: proc{|ds| ds.where(number: 1..10)}}).all
# SELECT * FROM artists
# SELECT * FROM albums WHERE (artist_id IN (...))
# SELECT * FROM tracks WHERE ((number >= 1) AND (number <= 10) AND (album_id IN (...)))

# For each artist, eager load albums with year > 1990, and tracks for those albums
Artist.eager(albums: {proc{|ds| ds.where{year > 1990}}=>:tracks}).all
# SELECT * FROM artists
# SELECT * FROM albums WHERE ((year > 1990) AND (artist_id IN (...)))
# SELECT * FROM albums WHERE (artist_id IN (...))
     # File lib/sequel/model/associations.rb
2973 def eager(*associations)
2974   opts = @opts[:eager]
2975   association_opts = eager_options_for_associations(associations)
2976   opts = opts ? opts.merge(association_opts) : association_opts
2977   clone(:eager=>opts.freeze)
2978 end
eager_graph(*associations) click to toggle source

The secondary eager loading method. Loads all associations in a single query. This method should only be used if you need to filter or order based on columns in associated tables, or if you have done comparative benchmarking it and determined it is faster.

This method uses Dataset#graph to create appropriate aliases for columns in all the tables. Then it uses the graph's metadata to build the associations from the single hash, and finally replaces the array of hashes with an array model objects inside all.

Be very careful when using this with multiple one_to_many or many_to_many associations, as you can create large cartesian products. If you must graph multiple one_to_many and many_to_many associations, make sure your filters are narrow if the datasets are large.

Each association's order, if defined, is respected. eager_graph probably won't work correctly on a limited dataset, unless you are only graphing many_to_one, one_to_one, and one_through_one associations.

Does not use the block defined for the association, since it does a single query for all objects. You can use the :graph_* association options to modify the SQL query.

Like eager, you need to call all on the dataset for the eager loading to work. If you just call each, it will yield plain hashes, each containing all columns from all the tables.

To modify the associated dataset that will be joined to the current dataset, you should use a hash for the association, with the key being the association name symbol, and the value being a callable object that is called with the associated dataset and should return a modified dataset. If that association also has dependent associations, instead of a callable object, use a hash with the callable object being the key, and the dependent association(s) as the value.

You can specify an custom alias and/or join type on a per-association basis by providing an Sequel::SQL::AliasedExpression object instead of an a Symbol for the association name.

Examples:

# For each album, eager_graph load the artist
Album.eager_graph(:artist).all
# SELECT ...
# FROM albums
# LEFT OUTER JOIN artists AS artist ON (artists.id = albums.artist_id)

# For each album, eager_graph load the artist, using a specified alias
Album.eager_graph(Sequel[:artist].as(:a)).all
# SELECT ...
# FROM albums
# LEFT OUTER JOIN artists AS a ON (a.id = albums.artist_id)

# For each album, eager_graph load the artist, using a specified alias
# and custom join type

Album.eager_graph(Sequel[:artist].as(:a, join_type: :inner)).all
# SELECT ...
# FROM albums
# INNER JOIN artists AS a ON (a.id = albums.artist_id)

# For each album, eager_graph load the artist and genre
Album.eager_graph(:artist, :genre).all
Album.eager_graph(:artist).eager_graph(:genre).all
# SELECT ...
# FROM albums
# LEFT OUTER JOIN artists AS artist ON (artist.id = albums.artist_id)
# LEFT OUTER JOIN genres AS genre ON (genre.id = albums.genre_id)

# For each artist, eager_graph load albums and tracks for each album
Artist.eager_graph(albums: :tracks).all
# SELECT ...
# FROM artists
# LEFT OUTER JOIN albums ON (albums.artist_id = artists.id)
# LEFT OUTER JOIN tracks ON (tracks.album_id = albums.id)

# For each artist, eager_graph load albums, tracks for each album, and genre for each track
Artist.eager_graph(albums: {tracks: :genre}).all
# SELECT ...
# FROM artists
# LEFT OUTER JOIN albums ON (albums.artist_id = artists.id)
# LEFT OUTER JOIN tracks ON (tracks.album_id = albums.id)
# LEFT OUTER JOIN genres AS genre ON (genre.id = tracks.genre_id)

# For each artist, eager_graph load albums with year > 1990
Artist.eager_graph(albums: proc{|ds| ds.where{year > 1990}}).all
# SELECT ...
# FROM artists
# LEFT OUTER JOIN (
#   SELECT * FROM albums WHERE (year > 1990)
# ) AS albums ON (albums.artist_id = artists.id)

# For each artist, eager_graph load albums and tracks 1-10 for each album
Artist.eager_graph(albums: {tracks: proc{|ds| ds.where(number: 1..10)}}).all
# SELECT ...
# FROM artists
# LEFT OUTER JOIN albums ON (albums.artist_id = artists.id)
# LEFT OUTER JOIN (
#   SELECT * FROM tracks WHERE ((number >= 1) AND (number <= 10))
# ) AS tracks ON (tracks.albums_id = albums.id)

# For each artist, eager_graph load albums with year > 1990, and tracks for those albums
Artist.eager_graph(albums: {proc{|ds| ds.where{year > 1990}}=>:tracks}).all
# SELECT ...
# FROM artists
# LEFT OUTER JOIN (
#   SELECT * FROM albums WHERE (year > 1990)
# ) AS albums ON (albums.artist_id = artists.id)
# LEFT OUTER JOIN tracks ON (tracks.album_id = albums.id)
     # File lib/sequel/model/associations.rb
3081 def eager_graph(*associations)
3082   eager_graph_with_options(associations)
3083 end
eager_graph_with_options(associations, opts=OPTS) click to toggle source

Run eager_graph with some options specific to just this call. Unlike eager_graph, this takes the associations as a single argument instead of multiple arguments.

Options:

:join_type

Override the join type specified in the association

:limit_strategy

Use a strategy for handling limits on associations. Appropriate :limit_strategy values are:

true

Pick the most appropriate based on what the database supports

:distinct_on

Force use of DISTINCT ON stategy (*_one associations only)

:correlated_subquery

Force use of correlated subquery strategy (one_to_* associations only)

:window_function

Force use of window function strategy

:ruby

Don't modify the SQL, implement limits/offsets with array slicing

This can also be a hash with association name symbol keys and one of the above values, to use different strategies per association.

The default is the :ruby strategy. Choosing a different strategy can make your code significantly slower in some cases (perhaps even the majority of cases), so you should only use this if you have benchmarked that it is faster for your use cases.

     # File lib/sequel/model/associations.rb
3105 def eager_graph_with_options(associations, opts=OPTS)
3106   return self if associations.empty?
3107 
3108   opts = opts.dup unless opts.frozen?
3109   associations = [associations] unless associations.is_a?(Array)
3110   ds = if eg = @opts[:eager_graph]
3111     eg = eg.dup
3112     [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup}
3113     eg[:local] = opts
3114     ds = clone(:eager_graph=>eg)
3115     ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations)
3116   else
3117     # Each of the following have a symbol key for the table alias, with the following values:
3118     # :reciprocals :: the reciprocal value to use for this association
3119     # :reflections :: AssociationReflection instance related to this association
3120     # :requirements :: array of requirements for this association
3121     # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading
3122     opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc}
3123     ds = clone(:eager_graph=>opts)
3124     ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked
3125   end
3126 
3127   ds.opts[:eager_graph].freeze
3128   ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)}
3129   ds
3130 end
to_hash_groups(key_column, value_column=nil, opts=OPTS) click to toggle source

If the dataset is being eagerly loaded, default to calling all instead of each.

Calls superclass method
     # File lib/sequel/model/associations.rb
3144 def to_hash_groups(key_column, value_column=nil, opts=OPTS)
3145   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3146     opts = Hash[opts]
3147     opts[:all] = true
3148   end
3149   super
3150 end
ungraphed() click to toggle source

Do not attempt to split the result set into associations, just return results as simple objects. This is useful if you want to use eager_graph as a shortcut to have all of the joins and aliasing set up, but want to do something else with the dataset.

Calls superclass method
     # File lib/sequel/model/associations.rb
3156 def ungraphed
3157   ds = super.clone(:eager_graph=>nil)
3158   if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc])
3159     ds = ds.with_row_proc(rp)
3160   end
3161   ds
3162 end

Protected Instance Methods

eager_graph_association(ds, model, ta, requirements, r, *associations) click to toggle source

Call graph on the association with the correct arguments, update the eager_graph data structure, and recurse into eager_graph_associations if there are any passed in associations (which would be dependencies of the current association)

Arguments:

ds

Current dataset

model

Current Model

ta

table_alias used for the parent association

requirements

an array, used as a stack for requirements

r

association reflection for the current association, or an SQL::AliasedExpression with the reflection as the expression, the alias base as the alias (or nil to use the default alias), and an optional hash with a :join_type entry as the columns to use a custom join type.

*associations

any associations dependent on this one

     # File lib/sequel/model/associations.rb
3181 def eager_graph_association(ds, model, ta, requirements, r, *associations)
3182   if r.is_a?(SQL::AliasedExpression)
3183     alias_base = r.alias
3184     if r.columns.is_a?(Hash)
3185       join_type = r.columns[:join_type]
3186     end
3187     r = r.expression
3188   else
3189     alias_base = r[:graph_alias_base]
3190   end
3191   assoc_table_alias = ds.unused_table_alias(alias_base)
3192   loader = r[:eager_grapher]
3193   if !associations.empty?
3194     if associations.first.respond_to?(:call)
3195       callback = associations.first
3196       associations = {}
3197     elsif associations.length == 1 && (assocs = associations.first).is_a?(Hash) && assocs.length == 1 && (pr_assoc = assocs.to_a.first) && pr_assoc.first.respond_to?(:call)
3198       callback, assoc = pr_assoc
3199       associations = assoc.is_a?(Array) ? assoc : [assoc]
3200     end
3201   end
3202   local_opts = ds.opts[:eager_graph][:local]
3203   limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy])
3204 
3205   if r[:conditions] && !Sequel.condition_specifier?(r[:conditions]) && !r[:orig_opts].has_key?(:graph_conditions) && !r[:orig_opts].has_key?(:graph_only_conditions) && !r.has_key?(:graph_block)
3206     raise Error, "Cannot eager_graph association when :conditions specified and not a hash or an array of pairs.  Specify :graph_conditions, :graph_only_conditions, or :graph_block for the association.  Model: #{r[:model]}, association: #{r[:name]}"
3207   end
3208 
3209   ds = loader.call(:self=>ds, :table_alias=>assoc_table_alias, :implicit_qualifier=>(ta == ds.opts[:eager_graph][:master]) ? first_source : qualifier_from_alias_symbol(ta, first_source), :callback=>callback, :join_type=>join_type || local_opts[:join_type], :join_only=>local_opts[:join_only], :limit_strategy=>limit_strategy, :from_self_alias=>ds.opts[:eager_graph][:master])
3210   if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order]))
3211     ds = ds.order_append(*qualified_expression(order, assoc_table_alias))
3212   end
3213   eager_graph = ds.opts[:eager_graph]
3214   eager_graph[:requirements][assoc_table_alias] = requirements.dup
3215   eager_graph[:reflections][assoc_table_alias] = r
3216   if limit_strategy == :ruby
3217     eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 
3218   end
3219   eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2
3220   ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty?
3221   ds
3222 end
eager_graph_associations(ds, model, ta, requirements, *associations) click to toggle source

Check the associations are valid for the given model. Call eager_graph_association on each association.

Arguments:

ds

Current dataset

model

Current Model

ta

table_alias used for the parent association

requirements

an array, used as a stack for requirements

*associations

the associations to add to the graph

     # File lib/sequel/model/associations.rb
3233 def eager_graph_associations(ds, model, ta, requirements, *associations)
3234   associations.flatten.each do |association|
3235     ds = case association
3236     when Symbol, SQL::AliasedExpression
3237       ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association))
3238     when Hash
3239       association.each do |assoc, assoc_assocs|
3240         ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs)
3241       end
3242       ds
3243     else
3244       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3245     end
3246   end
3247   ds
3248 end
eager_graph_build_associations(hashes) click to toggle source

Replace the array of plain hashes with an array of model objects will all eager_graphed associations set in the associations cache for each object.

     # File lib/sequel/model/associations.rb
3252 def eager_graph_build_associations(hashes)
3253   hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader))
3254 end

Private Instance Methods

_association_join(type, associations) click to toggle source

Return a new dataset with JOINs of the given type added, using the tables and conditions specified by the associations.

     # File lib/sequel/model/associations.rb
3260 def _association_join(type, associations)
3261   clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join])
3262 end
_eager_graph_build_associations(hashes, egl) click to toggle source

Process the array of hashes using the eager graph loader to return an array of model objects with the associations set.

     # File lib/sequel/model/associations.rb
3266 def _eager_graph_build_associations(hashes, egl)
3267   egl.load(hashes)
3268 end
add_association_filter_conditions(ref, obj, expr) click to toggle source

If the association has conditions itself, then it requires additional filters be added to the current dataset to ensure that the passed in object would also be included by the association's conditions.

     # File lib/sequel/model/associations.rb
3273 def add_association_filter_conditions(ref, obj, expr)
3274   if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions?
3275     Sequel[ref.filter_by_associations_conditions_expression(obj)]
3276   else
3277     expr
3278   end
3279 end
association_filter_expression(op, ref, obj) click to toggle source

Return an expression for filtering by the given association reflection and associated object.

     # File lib/sequel/model/associations.rb
3301 def association_filter_expression(op, ref, obj)
3302   meth = :"#{ref[:type]}_association_filter_expression"
3303   # Allow calling private association specific method to get filter expression
3304   send(meth, op, ref, obj) if respond_to?(meth, true)
3305 end
association_filter_handle_inversion(op, exp, cols) click to toggle source

Handle inversion for association filters by returning an inverted expression, plus also handling cases where the referenced columns are NULL.

     # File lib/sequel/model/associations.rb
3309 def association_filter_handle_inversion(op, exp, cols)
3310   if op == :'!=' || op == :'NOT IN'
3311     if exp == SQL::Constants::FALSE
3312       ~exp
3313     else
3314       ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR)
3315     end
3316   else
3317     exp
3318   end
3319 end
association_filter_key_expression(keys, meths, obj) click to toggle source

Return an expression for making sure that the given keys match the value of the given methods for either the single object given or for any of the objects given if obj is an array.

     # File lib/sequel/model/associations.rb
3324 def association_filter_key_expression(keys, meths, obj)
3325   vals = if obj.is_a?(Sequel::Dataset)
3326     {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))}
3327   else
3328     vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}}
3329     return SQL::Constants::FALSE if vals.empty?
3330     if obj.is_a?(Array)
3331       if keys.length == 1
3332         meth = meths.first
3333         {keys.first=>vals.map{|o| o.get_column_value(meth)}}
3334       else
3335         {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}}
3336       end  
3337     else
3338       keys.zip(meths.map{|k| obj.get_column_value(k)})
3339     end
3340   end
3341   SQL::BooleanExpression.from_value_pairs(vals)
3342 end
check_association(model, association) click to toggle source

Make sure the association is valid for this model, and return the related AssociationReflection.

     # File lib/sequel/model/associations.rb
3345 def check_association(model, association)
3346   raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association)
3347   raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false
3348   reflection
3349 end
eager_graph_check_association(model, association) click to toggle source

Allow associations that are eagerly graphed to be specified as an SQL::AliasedExpression, for per-call determining of the alias base.

     # File lib/sequel/model/associations.rb
3353 def eager_graph_check_association(model, association)
3354   if association.is_a?(SQL::AliasedExpression)
3355     expr = association.expression
3356     if expr.is_a?(SQL::Identifier)
3357       expr = expr.value
3358       if expr.is_a?(String)
3359         expr = expr.to_sym
3360       end
3361     end
3362 
3363     SQL::AliasedExpression.new(check_association(model, expr), association.alias || expr, association.columns)
3364   else
3365     check_association(model, association)
3366   end
3367 end
eager_graph_loader() click to toggle source

The EagerGraphLoader instance used for converting eager_graph results.

     # File lib/sequel/model/associations.rb
3370 def eager_graph_loader
3371   unless egl = cache_get(:_model_eager_graph_loader)
3372     egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self))
3373   end
3374   egl.dup
3375 end
eager_load(a, eager_assoc=@opts[:eager]) click to toggle source

Eagerly load all specified associations

     # File lib/sequel/model/associations.rb
3378 def eager_load(a, eager_assoc=@opts[:eager])
3379   return if a.empty?
3380   # Key is foreign/primary key name symbol.
3381   # Value is hash with keys being foreign/primary key values (generally integers)
3382   # and values being an array of current model objects with that specific foreign/primary key
3383   key_hash = {}
3384   # Reflections for all associations to eager load
3385   reflections = eager_assoc.keys.map{|assoc| model.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")}
3386       
3387   # Populate the key_hash entry for each association being eagerly loaded
3388   reflections.each do |r|
3389     if key = r.eager_loader_key
3390       # key_hash for this key has already been populated,
3391       # skip populating again so that duplicate values
3392       # aren't added.
3393       unless id_map = key_hash[key]
3394         id_map = key_hash[key] = Hash.new{|h,k| h[k] = []}
3395 
3396         # Supporting both single (Symbol) and composite (Array) keys.
3397         a.each do |rec|
3398           case key
3399           when Array
3400             if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all?
3401               id_map[k] << rec
3402             end
3403           when Symbol
3404             if k = rec.get_column_value(key)
3405               id_map[k] << rec
3406             end
3407           else
3408             raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}"
3409           end
3410         end
3411       end
3412     else
3413       id_map = nil
3414     end
3415   
3416     loader = r[:eager_loader]
3417     associations = eager_assoc[r[:name]]
3418     if associations.respond_to?(:call)
3419       eager_block = associations
3420       associations = OPTS
3421     elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call)
3422       eager_block, associations = pr_assoc
3423     end
3424     loader.call(:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map)
3425     a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load]
3426   end 
3427 end
eager_options_for_associations(associations) click to toggle source

Process the array of associations arguments (Symbols, Arrays, and Hashes), and return a hash of options suitable for cascading.

     # File lib/sequel/model/associations.rb
3283 def eager_options_for_associations(associations)
3284   opts = {}
3285   associations.flatten.each do |association|
3286     case association
3287     when Symbol
3288       check_association(model, association)
3289       opts[association] = nil
3290     when Hash
3291       association.keys.each{|assoc| check_association(model, assoc)}
3292       opts.merge!(association)
3293     else
3294       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3295     end
3296   end
3297   opts
3298 end
many_to_many_association_filter_expression(op, ref, obj) click to toggle source

Return a subquery expression for filering by a many_to_many association

     # File lib/sequel/model/associations.rb
3430 def many_to_many_association_filter_expression(op, ref, obj)
3431   lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys)
3432   jt = ref.join_table_alias
3433   lpks = lpks.first if lpks.length == 1
3434   lpks = ref.qualify(model.table_name, lpks)
3435 
3436   meths = if obj.is_a?(Sequel::Dataset)
3437     ref.qualify(obj.model.table_name, ref.right_primary_keys)
3438   else
3439     ref.right_primary_key_methods
3440   end
3441 
3442   expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj)
3443   unless expr == SQL::Constants::FALSE
3444     expr = SQL::BooleanExpression.from_value_pairs(lpks=>model.db.from(ref[:join_table]).select(*ref.qualify(jt, lks)).where(expr).exclude(SQL::BooleanExpression.from_value_pairs(ref.qualify(jt, lks).zip([]), :OR)))
3445     expr = add_association_filter_conditions(ref, obj, expr)
3446   end
3447 
3448   association_filter_handle_inversion(op, expr, Array(lpks))
3449 end
many_to_one_association_filter_expression(op, ref, obj) click to toggle source

Return a simple equality expression for filering by a many_to_one association

     # File lib/sequel/model/associations.rb
3453 def many_to_one_association_filter_expression(op, ref, obj)
3454   keys = ref.qualify(model.table_name, ref[:key_columns])
3455   meths = if obj.is_a?(Sequel::Dataset)
3456     ref.qualify(obj.model.table_name, ref.primary_keys)
3457   else
3458     ref.primary_key_methods
3459   end
3460 
3461   expr = association_filter_key_expression(keys, meths, obj)
3462   expr = add_association_filter_conditions(ref, obj, expr)
3463   association_filter_handle_inversion(op, expr, keys)
3464 end
non_sql_option?(key) click to toggle source
Calls superclass method
     # File lib/sequel/model/associations.rb
3481 def non_sql_option?(key)
3482   super || key == :eager || key == :eager_graph
3483 end
one_through_one_association_filter_expression(op, ref, obj)
one_to_many_association_filter_expression(op, ref, obj) click to toggle source

Return a simple equality expression for filering by a one_to_* association

     # File lib/sequel/model/associations.rb
3467 def one_to_many_association_filter_expression(op, ref, obj)
3468   keys = ref.qualify(model.table_name, ref[:primary_key_columns])
3469   meths = if obj.is_a?(Sequel::Dataset)
3470     ref.qualify(obj.model.table_name, ref[:keys])
3471   else
3472     ref[:key_methods]
3473   end
3474 
3475   expr = association_filter_key_expression(keys, meths, obj)
3476   expr = add_association_filter_conditions(ref, obj, expr)
3477   association_filter_handle_inversion(op, expr, keys)
3478 end
one_to_one_association_filter_expression(op, ref, obj)
post_load(all_records) click to toggle source

Build associations from the graph if eager_graph was used, and/or load other associations if eager was used.

Calls superclass method
     # File lib/sequel/model/associations.rb
3487 def post_load(all_records)
3488   eager_graph_build_associations(all_records) if @opts[:eager_graph]
3489   eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph])
3490   super
3491 end