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
3319 def as_hash(key_column=nil, value_column=nil, opts=OPTS)
3320   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3321     opts = Hash[opts]
3322     opts[:all] = true
3323   end
3324   super
3325 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
3025 def association_join(*associations)
3026   association_inner_join(*associations)
3027 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
3036 def complex_expression_sql_append(sql, op, args)
3037   r = args[1]
3038   if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) ||
3039       (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)})))))
3040     l = args[0]
3041     if ar = model.association_reflections[l]
3042       raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false
3043 
3044       if multiple
3045         klass = ar.associated_class
3046         if is_ds
3047           if r.respond_to?(:model)
3048             unless r.model <= klass
3049               # A dataset for a different model class, could be a valid regular query
3050               return super
3051             end
3052           else
3053             # Not a model dataset, could be a valid regular query
3054             return super
3055           end
3056         else
3057           unless r.all?{|x| x.is_a?(klass)}
3058             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}"
3059           end
3060         end
3061       elsif !r.is_a?(ar.associated_class)
3062         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}"
3063       end
3064 
3065       if exp = association_filter_expression(op, ar, r)
3066         literal_append(sql, exp)
3067       else
3068         raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}"
3069       end
3070     elsif multiple && (is_ds || r.empty?)
3071       # Not a query designed for this support, could be a valid regular query
3072       super
3073     else
3074       raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}"
3075     end
3076   else
3077     super
3078   end
3079 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
3156 def eager(*associations)
3157   opts = @opts[:eager]
3158   association_opts = eager_options_for_associations(associations)
3159   opts = opts ? opts.merge(association_opts) : association_opts
3160   clone(:eager=>opts.freeze)
3161 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 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.

You cannot mix calls to eager_graph and graph on the same dataset.

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
3266 def eager_graph(*associations)
3267   eager_graph_with_options(associations)
3268 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
3290 def eager_graph_with_options(associations, opts=OPTS)
3291   return self if associations.empty?
3292 
3293   opts = opts.dup unless opts.frozen?
3294   associations = [associations] unless associations.is_a?(Array)
3295   ds = if eg = @opts[:eager_graph]
3296     eg = eg.dup
3297     [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup}
3298     eg[:local] = opts
3299     ds = clone(:eager_graph=>eg)
3300     ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations)
3301   else
3302     # Each of the following have a symbol key for the table alias, with the following values:
3303     # :reciprocals :: the reciprocal value to use for this association
3304     # :reflections :: AssociationReflection instance related to this association
3305     # :requirements :: array of requirements for this association
3306     # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading
3307     opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc}
3308     ds = clone(:eager_graph=>opts)
3309     ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked
3310   end
3311 
3312   ds.opts[:eager_graph].freeze
3313   ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)}
3314   ds
3315 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
3329 def to_hash_groups(key_column, value_column=nil, opts=OPTS)
3330   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3331     opts = Hash[opts]
3332     opts[:all] = true
3333   end
3334   super
3335 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
3341 def ungraphed
3342   ds = super.clone(:eager_graph=>nil)
3343   if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc])
3344     ds = ds.with_row_proc(rp)
3345   end
3346   ds
3347 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
3366 def eager_graph_association(ds, model, ta, requirements, r, *associations)
3367   if r.is_a?(SQL::AliasedExpression)
3368     alias_base = r.alias
3369     if r.columns.is_a?(Hash)
3370       join_type = r.columns[:join_type]
3371     end
3372     r = r.expression
3373   else
3374     alias_base = r[:graph_alias_base]
3375   end
3376   assoc_table_alias = ds.unused_table_alias(alias_base)
3377   loader = r[:eager_grapher]
3378   if !associations.empty?
3379     if associations.first.respond_to?(:call)
3380       callback = associations.first
3381       associations = {}
3382     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)
3383       callback, assoc = pr_assoc
3384       associations = assoc.is_a?(Array) ? assoc : [assoc]
3385     end
3386   end
3387   local_opts = ds.opts[:eager_graph][:local]
3388   limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy])
3389 
3390   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)
3391     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]}"
3392   end
3393 
3394   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])
3395   if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order]))
3396     ds = ds.order_append(*qualified_expression(order, assoc_table_alias))
3397   end
3398   eager_graph = ds.opts[:eager_graph]
3399   eager_graph[:requirements][assoc_table_alias] = requirements.dup
3400   eager_graph[:reflections][assoc_table_alias] = r
3401   if limit_strategy == :ruby
3402     eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 
3403   end
3404   eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2
3405   ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty?
3406   ds
3407 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
3418 def eager_graph_associations(ds, model, ta, requirements, *associations)
3419   associations.flatten.each do |association|
3420     ds = case association
3421     when Symbol, SQL::AliasedExpression
3422       ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association))
3423     when Hash
3424       association.each do |assoc, assoc_assocs|
3425         ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs)
3426       end
3427       ds
3428     else
3429       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3430     end
3431   end
3432   ds
3433 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
3437 def eager_graph_build_associations(hashes)
3438   hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader))
3439 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
3445 def _association_join(type, associations)
3446   clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join])
3447 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
3451 def _eager_graph_build_associations(hashes, egl)
3452   egl.load(hashes)
3453 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
3458 def add_association_filter_conditions(ref, obj, expr)
3459   if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions?
3460     Sequel[ref.filter_by_associations_conditions_expression(obj)]
3461   else
3462     expr
3463   end
3464 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
3486 def association_filter_expression(op, ref, obj)
3487   meth = :"#{ref[:type]}_association_filter_expression"
3488   # Allow calling private association specific method to get filter expression
3489   send(meth, op, ref, obj) if respond_to?(meth, true)
3490 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
3494 def association_filter_handle_inversion(op, exp, cols)
3495   if op == :'!=' || op == :'NOT IN'
3496     if exp == SQL::Constants::FALSE
3497       ~exp
3498     else
3499       ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR)
3500     end
3501   else
3502     exp
3503   end
3504 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
3509 def association_filter_key_expression(keys, meths, obj)
3510   vals = if obj.is_a?(Sequel::Dataset)
3511     {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))}
3512   else
3513     vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}}
3514     return SQL::Constants::FALSE if vals.empty?
3515     if obj.is_a?(Array)
3516       if keys.length == 1
3517         meth = meths.first
3518         {keys.first=>vals.map{|o| o.get_column_value(meth)}}
3519       else
3520         {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}}
3521       end  
3522     else
3523       keys.zip(meths.map{|k| obj.get_column_value(k)})
3524     end
3525   end
3526   SQL::BooleanExpression.from_value_pairs(vals)
3527 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
3530 def check_association(model, association)
3531   raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association)
3532   raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false
3533   reflection
3534 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
3538 def eager_graph_check_association(model, association)
3539   reflection = if association.is_a?(SQL::AliasedExpression)
3540     expr = association.expression
3541     if expr.is_a?(SQL::Identifier)
3542       expr = expr.value
3543       if expr.is_a?(String)
3544         expr = expr.to_sym
3545       end
3546     end
3547 
3548     check_reflection = check_association(model, expr)
3549     SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns)
3550   else
3551     check_reflection = check_association(model, association)
3552   end
3553 
3554   if check_reflection && check_reflection[:allow_eager_graph] == false
3555     raise Error, "eager_graph not allowed for #{reflection.inspect}"
3556   end
3557 
3558   reflection
3559 end
eager_graph_loader() click to toggle source

The EagerGraphLoader instance used for converting eager_graph results.

     # File lib/sequel/model/associations.rb
3562 def eager_graph_loader
3563   unless egl = cache_get(:_model_eager_graph_loader)
3564     egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self))
3565   end
3566   egl.dup
3567 end
eager_load(a, eager_assoc=@opts[:eager], m=model) click to toggle source

Eagerly load all specified associations.

     # File lib/sequel/model/associations.rb
3570 def eager_load(a, eager_assoc=@opts[:eager], m=model)
3571   return if a.empty?
3572 
3573   # Reflections for all associations to eager load
3574   reflections = eager_assoc.keys.map{|assoc| m.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")}
3575 
3576   perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc))
3577 
3578   reflections.each do |r|
3579     a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load]
3580   end 
3581 
3582   nil
3583 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
3468 def eager_options_for_associations(associations)
3469   opts = {}
3470   associations.flatten.each do |association|
3471     case association
3472     when Symbol
3473       check_association(model, association)
3474       opts[association] = nil
3475     when Hash
3476       association.keys.each{|assoc| check_association(model, assoc)}
3477       opts.merge!(association)
3478     else
3479       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3480     end
3481   end
3482   opts
3483 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
3650 def many_to_many_association_filter_expression(op, ref, obj)
3651   lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys)
3652   jt = ref.join_table_alias
3653   lpks = lpks.first if lpks.length == 1
3654   lpks = ref.qualify(model.table_name, lpks)
3655 
3656   meths = if obj.is_a?(Sequel::Dataset)
3657     ref.qualify(obj.model.table_name, ref.right_primary_keys)
3658   else
3659     ref.right_primary_key_methods
3660   end
3661 
3662   expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj)
3663   unless expr == SQL::Constants::FALSE
3664     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)))
3665     expr = add_association_filter_conditions(ref, obj, expr)
3666   end
3667 
3668   association_filter_handle_inversion(op, expr, Array(lpks))
3669 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
3673 def many_to_one_association_filter_expression(op, ref, obj)
3674   keys = ref.qualify(model.table_name, ref[:key_columns])
3675   meths = if obj.is_a?(Sequel::Dataset)
3676     ref.qualify(obj.model.table_name, ref.primary_keys)
3677   else
3678     ref.primary_key_methods
3679   end
3680 
3681   expr = association_filter_key_expression(keys, meths, obj)
3682   expr = add_association_filter_conditions(ref, obj, expr)
3683   association_filter_handle_inversion(op, expr, keys)
3684 end
non_sql_option?(key) click to toggle source
Calls superclass method
     # File lib/sequel/model/associations.rb
3701 def non_sql_option?(key)
3702   super || key == :eager || key == :eager_graph
3703 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
3687 def one_to_many_association_filter_expression(op, ref, obj)
3688   keys = ref.qualify(model.table_name, ref[:primary_key_columns])
3689   meths = if obj.is_a?(Sequel::Dataset)
3690     ref.qualify(obj.model.table_name, ref[:keys])
3691   else
3692     ref[:key_methods]
3693   end
3694 
3695   expr = association_filter_key_expression(keys, meths, obj)
3696   expr = add_association_filter_conditions(ref, obj, expr)
3697   association_filter_handle_inversion(op, expr, keys)
3698 end
one_to_one_association_filter_expression(op, ref, obj)
perform_eager_load(loader, eo) click to toggle source

Perform eager loading for a single association using the loader and eager options.

     # File lib/sequel/model/associations.rb
3645 def perform_eager_load(loader, eo)
3646   loader.call(eo)
3647 end
perform_eager_loads(eager_load_data) click to toggle source

Using the hash of loaders and eager options, perform the eager loading.

     # File lib/sequel/model/associations.rb
3638 def perform_eager_loads(eager_load_data)
3639   eager_load_data.map do |loader, eo|
3640     perform_eager_load(loader, eo)
3641   end
3642 end
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
3707 def post_load(all_records)
3708   eager_graph_build_associations(all_records) if @opts[:eager_graph]
3709   eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph])
3710   super
3711 end
prepare_eager_load(a, reflections, eager_assoc) click to toggle source

Prepare a hash loaders and eager options which will be used to implement the eager loading.

     # File lib/sequel/model/associations.rb
3586 def prepare_eager_load(a, reflections, eager_assoc)
3587   eager_load_data = {}
3588 
3589   # Key is foreign/primary key name symbol.
3590   # Value is hash with keys being foreign/primary key values (generally integers)
3591   # and values being an array of current model objects with that specific foreign/primary key
3592   key_hash = {}
3593       
3594   # Populate the key_hash entry for each association being eagerly loaded
3595   reflections.each do |r|
3596     if key = r.eager_loader_key
3597       # key_hash for this key has already been populated,
3598       # skip populating again so that duplicate values
3599       # aren't added.
3600       unless id_map = key_hash[key]
3601         id_map = key_hash[key] = Hash.new{|h,k| h[k] = []}
3602 
3603         # Supporting both single (Symbol) and composite (Array) keys.
3604         a.each do |rec|
3605           case key
3606           when Array
3607             if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all?
3608               id_map[k] << rec
3609             end
3610           when Symbol
3611             if k = rec.get_column_value(key)
3612               id_map[k] << rec
3613             end
3614           else
3615             raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}"
3616           end
3617         end
3618       end
3619     else
3620       id_map = nil
3621     end
3622   
3623     associations = eager_assoc[r[:name]]
3624     if associations.respond_to?(:call)
3625       eager_block = associations
3626       associations = OPTS
3627     elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call)
3628       eager_block, associations = pr_assoc
3629     end
3630 
3631     eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map}
3632   end
3633 
3634   eager_load_data
3635 end