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
3110 def as_hash(key_column=nil, value_column=nil, opts=OPTS)
3111   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3112     opts = Hash[opts]
3113     opts[:all] = true
3114   end
3115   super
3116 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
2820 def association_join(*associations)
2821   association_inner_join(*associations)
2822 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
2831 def complex_expression_sql_append(sql, op, args)
2832   r = args[1]
2833   if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) ||
2834       (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)})))))
2835     l = args[0]
2836     if ar = model.association_reflections[l]
2837       if multiple
2838         klass = ar.associated_class
2839         if is_ds
2840           if r.respond_to?(:model)
2841             unless r.model <= klass
2842               # A dataset for a different model class, could be a valid regular query
2843               return super
2844             end
2845           else
2846             # Not a model dataset, could be a valid regular query
2847             return super
2848           end
2849         else
2850           unless r.all?{|x| x.is_a?(klass)}
2851             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}"
2852           end
2853         end
2854       elsif !r.is_a?(ar.associated_class)
2855         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}"
2856       end
2857 
2858       if exp = association_filter_expression(op, ar, r)
2859         literal_append(sql, exp)
2860       else
2861         raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}"
2862       end
2863     elsif multiple && (is_ds || r.empty?)
2864       # Not a query designed for this support, could be a valid regular query
2865       super
2866     else
2867       raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}"
2868     end
2869   else
2870     super
2871   end
2872 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
2949 def eager(*associations)
2950   opts = @opts[:eager]
2951   association_opts = eager_options_for_associations(associations)
2952   opts = opts ? opts.merge(association_opts) : association_opts
2953   clone(:eager=>opts.freeze)
2954 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
3057 def eager_graph(*associations)
3058   eager_graph_with_options(associations)
3059 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
3081 def eager_graph_with_options(associations, opts=OPTS)
3082   return self if associations.empty?
3083 
3084   opts = opts.dup unless opts.frozen?
3085   associations = [associations] unless associations.is_a?(Array)
3086   ds = if eg = @opts[:eager_graph]
3087     eg = eg.dup
3088     [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup}
3089     eg[:local] = opts
3090     ds = clone(:eager_graph=>eg)
3091     ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations)
3092   else
3093     # Each of the following have a symbol key for the table alias, with the following values:
3094     # :reciprocals :: the reciprocal value to use for this association
3095     # :reflections :: AssociationReflection instance related to this association
3096     # :requirements :: array of requirements for this association
3097     # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading
3098     opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc}
3099     ds = clone(:eager_graph=>opts)
3100     ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked
3101   end
3102 
3103   ds.opts[:eager_graph].freeze
3104   ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)}
3105   ds
3106 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
3120 def to_hash_groups(key_column, value_column=nil, opts=OPTS)
3121   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3122     opts = Hash[opts]
3123     opts[:all] = true
3124   end
3125   super
3126 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
3132 def ungraphed
3133   ds = super.clone(:eager_graph=>nil)
3134   if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc])
3135     ds = ds.with_row_proc(rp)
3136   end
3137   ds
3138 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
3157 def eager_graph_association(ds, model, ta, requirements, r, *associations)
3158   if r.is_a?(SQL::AliasedExpression)
3159     alias_base = r.alias
3160     if r.columns.is_a?(Hash)
3161       join_type = r.columns[:join_type]
3162     end
3163     r = r.expression
3164   else
3165     alias_base = r[:graph_alias_base]
3166   end
3167   assoc_table_alias = ds.unused_table_alias(alias_base)
3168   loader = r[:eager_grapher]
3169   if !associations.empty?
3170     if associations.first.respond_to?(:call)
3171       callback = associations.first
3172       associations = {}
3173     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)
3174       callback, assoc = pr_assoc
3175       associations = assoc.is_a?(Array) ? assoc : [assoc]
3176     end
3177   end
3178   local_opts = ds.opts[:eager_graph][:local]
3179   limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy])
3180 
3181   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)
3182     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]}"
3183   end
3184 
3185   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])
3186   if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order]))
3187     ds = ds.order_append(*qualified_expression(order, assoc_table_alias))
3188   end
3189   eager_graph = ds.opts[:eager_graph]
3190   eager_graph[:requirements][assoc_table_alias] = requirements.dup
3191   eager_graph[:reflections][assoc_table_alias] = r
3192   if limit_strategy == :ruby
3193     eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 
3194   end
3195   eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2
3196   ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty?
3197   ds
3198 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
3209 def eager_graph_associations(ds, model, ta, requirements, *associations)
3210   associations.flatten.each do |association|
3211     ds = case association
3212     when Symbol, SQL::AliasedExpression
3213       ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association))
3214     when Hash
3215       association.each do |assoc, assoc_assocs|
3216         ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs)
3217       end
3218       ds
3219     else
3220       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3221     end
3222   end
3223   ds
3224 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
3228 def eager_graph_build_associations(hashes)
3229   hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader))
3230 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
3236 def _association_join(type, associations)
3237   clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join])
3238 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
3242 def _eager_graph_build_associations(hashes, egl)
3243   egl.load(hashes)
3244 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
3249 def add_association_filter_conditions(ref, obj, expr)
3250   if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions?
3251     Sequel[ref.filter_by_associations_conditions_expression(obj)]
3252   else
3253     expr
3254   end
3255 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
3277 def association_filter_expression(op, ref, obj)
3278   meth = :"#{ref[:type]}_association_filter_expression"
3279   # Allow calling private association specific method to get filter expression
3280   send(meth, op, ref, obj) if respond_to?(meth, true)
3281 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
3285 def association_filter_handle_inversion(op, exp, cols)
3286   if op == :'!=' || op == :'NOT IN'
3287     if exp == SQL::Constants::FALSE
3288       ~exp
3289     else
3290       ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR)
3291     end
3292   else
3293     exp
3294   end
3295 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
3300 def association_filter_key_expression(keys, meths, obj)
3301   vals = if obj.is_a?(Sequel::Dataset)
3302     {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))}
3303   else
3304     vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}}
3305     return SQL::Constants::FALSE if vals.empty?
3306     if obj.is_a?(Array)
3307       if keys.length == 1
3308         meth = meths.first
3309         {keys.first=>vals.map{|o| o.get_column_value(meth)}}
3310       else
3311         {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}}
3312       end  
3313     else
3314       keys.zip(meths.map{|k| obj.get_column_value(k)})
3315     end
3316   end
3317   SQL::BooleanExpression.from_value_pairs(vals)
3318 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
3321 def check_association(model, association)
3322   raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association)
3323   raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false
3324   reflection
3325 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
3329 def eager_graph_check_association(model, association)
3330   if association.is_a?(SQL::AliasedExpression)
3331     expr = association.expression
3332     if expr.is_a?(SQL::Identifier)
3333       expr = expr.value
3334       if expr.is_a?(String)
3335         expr = expr.to_sym
3336       end
3337     end
3338 
3339     SQL::AliasedExpression.new(check_association(model, expr), association.alias || expr, association.columns)
3340   else
3341     check_association(model, association)
3342   end
3343 end
eager_graph_loader() click to toggle source

The EagerGraphLoader instance used for converting eager_graph results.

     # File lib/sequel/model/associations.rb
3346 def eager_graph_loader
3347   unless egl = cache_get(:_model_eager_graph_loader)
3348     egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self))
3349   end
3350   egl.dup
3351 end
eager_load(a, eager_assoc=@opts[:eager]) click to toggle source

Eagerly load all specified associations

     # File lib/sequel/model/associations.rb
3354 def eager_load(a, eager_assoc=@opts[:eager])
3355   return if a.empty?
3356   # Key is foreign/primary key name symbol.
3357   # Value is hash with keys being foreign/primary key values (generally integers)
3358   # and values being an array of current model objects with that specific foreign/primary key
3359   key_hash = {}
3360   # Reflections for all associations to eager load
3361   reflections = eager_assoc.keys.map{|assoc| model.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")}
3362       
3363   # Populate the key_hash entry for each association being eagerly loaded
3364   reflections.each do |r|
3365     if key = r.eager_loader_key
3366       # key_hash for this key has already been populated,
3367       # skip populating again so that duplicate values
3368       # aren't added.
3369       unless id_map = key_hash[key]
3370         id_map = key_hash[key] = Hash.new{|h,k| h[k] = []}
3371 
3372         # Supporting both single (Symbol) and composite (Array) keys.
3373         a.each do |rec|
3374           case key
3375           when Array
3376             if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all?
3377               id_map[k] << rec
3378             end
3379           when Symbol
3380             if k = rec.get_column_value(key)
3381               id_map[k] << rec
3382             end
3383           else
3384             raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}"
3385           end
3386         end
3387       end
3388     else
3389       id_map = nil
3390     end
3391   
3392     loader = r[:eager_loader]
3393     associations = eager_assoc[r[:name]]
3394     if associations.respond_to?(:call)
3395       eager_block = associations
3396       associations = OPTS
3397     elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call)
3398       eager_block, associations = pr_assoc
3399     end
3400     loader.call(:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map)
3401     a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load]
3402   end 
3403 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
3259 def eager_options_for_associations(associations)
3260   opts = {}
3261   associations.flatten.each do |association|
3262     case association
3263     when Symbol
3264       check_association(model, association)
3265       opts[association] = nil
3266     when Hash
3267       association.keys.each{|assoc| check_association(model, assoc)}
3268       opts.merge!(association)
3269     else
3270       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3271     end
3272   end
3273   opts
3274 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
3406 def many_to_many_association_filter_expression(op, ref, obj)
3407   lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys)
3408   jt = ref.join_table_alias
3409   lpks = lpks.first if lpks.length == 1
3410   lpks = ref.qualify(model.table_name, lpks)
3411 
3412   meths = if obj.is_a?(Sequel::Dataset)
3413     ref.qualify(obj.model.table_name, ref.right_primary_keys)
3414   else
3415     ref.right_primary_key_methods
3416   end
3417 
3418   expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj)
3419   unless expr == SQL::Constants::FALSE
3420     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)))
3421     expr = add_association_filter_conditions(ref, obj, expr)
3422   end
3423 
3424   association_filter_handle_inversion(op, expr, Array(lpks))
3425 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
3429 def many_to_one_association_filter_expression(op, ref, obj)
3430   keys = ref.qualify(model.table_name, ref[:key_columns])
3431   meths = if obj.is_a?(Sequel::Dataset)
3432     ref.qualify(obj.model.table_name, ref.primary_keys)
3433   else
3434     ref.primary_key_methods
3435   end
3436 
3437   expr = association_filter_key_expression(keys, meths, obj)
3438   expr = add_association_filter_conditions(ref, obj, expr)
3439   association_filter_handle_inversion(op, expr, keys)
3440 end
non_sql_option?(key) click to toggle source
Calls superclass method
     # File lib/sequel/model/associations.rb
3457 def non_sql_option?(key)
3458   super || key == :eager || key == :eager_graph
3459 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
3443 def one_to_many_association_filter_expression(op, ref, obj)
3444   keys = ref.qualify(model.table_name, ref[:primary_key_columns])
3445   meths = if obj.is_a?(Sequel::Dataset)
3446     ref.qualify(obj.model.table_name, ref[:keys])
3447   else
3448     ref[:key_methods]
3449   end
3450 
3451   expr = association_filter_key_expression(keys, meths, obj)
3452   expr = add_association_filter_conditions(ref, obj, expr)
3453   association_filter_handle_inversion(op, expr, keys)
3454 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
3463 def post_load(all_records)
3464   eager_graph_build_associations(all_records) if @opts[:eager_graph]
3465   eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph])
3466   super
3467 end