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
3344 def as_hash(key_column=nil, value_column=nil, opts=OPTS)
3345   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3346     opts = Hash[opts]
3347     opts[:all] = true
3348   end
3349   super
3350 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
3050 def association_join(*associations)
3051   association_inner_join(*associations)
3052 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
3061 def complex_expression_sql_append(sql, op, args)
3062   r = args[1]
3063   if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) ||
3064       (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)})))))
3065     l = args[0]
3066     if ar = model.association_reflections[l]
3067       raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false
3068 
3069       if multiple
3070         klass = ar.associated_class
3071         if is_ds
3072           if r.respond_to?(:model)
3073             unless r.model <= klass
3074               # A dataset for a different model class, could be a valid regular query
3075               return super
3076             end
3077           else
3078             # Not a model dataset, could be a valid regular query
3079             return super
3080           end
3081         else
3082           unless r.all?{|x| x.is_a?(klass)}
3083             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}"
3084           end
3085         end
3086       elsif !r.is_a?(ar.associated_class)
3087         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}"
3088       end
3089 
3090       if exp = association_filter_expression(op, ar, r)
3091         literal_append(sql, exp)
3092       else
3093         raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}"
3094       end
3095     elsif multiple && (is_ds || r.empty?)
3096       # Not a query designed for this support, could be a valid regular query
3097       super
3098     else
3099       raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}"
3100     end
3101   else
3102     super
3103   end
3104 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
3181 def eager(*associations)
3182   opts = @opts[:eager]
3183   association_opts = eager_options_for_associations(associations)
3184   opts = opts ? opts.merge(association_opts) : association_opts
3185   clone(:eager=>opts.freeze)
3186 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
3291 def eager_graph(*associations)
3292   eager_graph_with_options(associations)
3293 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
3315 def eager_graph_with_options(associations, opts=OPTS)
3316   return self if associations.empty?
3317 
3318   opts = opts.dup unless opts.frozen?
3319   associations = [associations] unless associations.is_a?(Array)
3320   ds = if eg = @opts[:eager_graph]
3321     eg = eg.dup
3322     [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup}
3323     eg[:local] = opts
3324     ds = clone(:eager_graph=>eg)
3325     ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations)
3326   else
3327     # Each of the following have a symbol key for the table alias, with the following values:
3328     # :reciprocals :: the reciprocal value to use for this association
3329     # :reflections :: AssociationReflection instance related to this association
3330     # :requirements :: array of requirements for this association
3331     # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading
3332     opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc}
3333     ds = clone(:eager_graph=>opts)
3334     ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked
3335   end
3336 
3337   ds.opts[:eager_graph].freeze
3338   ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)}
3339   ds
3340 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
3354 def to_hash_groups(key_column, value_column=nil, opts=OPTS)
3355   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3356     opts = Hash[opts]
3357     opts[:all] = true
3358   end
3359   super
3360 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
3366 def ungraphed
3367   ds = super.clone(:eager_graph=>nil)
3368   if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc])
3369     ds = ds.with_row_proc(rp)
3370   end
3371   ds
3372 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
3391 def eager_graph_association(ds, model, ta, requirements, r, *associations)
3392   if r.is_a?(SQL::AliasedExpression)
3393     alias_base = r.alias
3394     if r.columns.is_a?(Hash)
3395       join_type = r.columns[:join_type]
3396     end
3397     r = r.expression
3398   else
3399     alias_base = r[:graph_alias_base]
3400   end
3401   assoc_table_alias = ds.unused_table_alias(alias_base)
3402   loader = r[:eager_grapher]
3403   if !associations.empty?
3404     if associations.first.respond_to?(:call)
3405       callback = associations.first
3406       associations = {}
3407     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)
3408       callback, assoc = pr_assoc
3409       associations = assoc.is_a?(Array) ? assoc : [assoc]
3410     end
3411   end
3412   local_opts = ds.opts[:eager_graph][:local]
3413   limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy])
3414 
3415   # SEQUEL6: remove and integrate the auto_restrict_eager_graph plugin
3416   if !r[:orig_opts].has_key?(:graph_conditions) && !r[:orig_opts].has_key?(:graph_only_conditions) && !r.has_key?(:graph_block) && !r[:allow_eager_graph]
3417     if r[:conditions] && !Sequel.condition_specifier?(r[:conditions])
3418       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]}"
3419     end
3420 
3421     if r[:block] && !r[:graph_use_association_block]
3422       warn "eager_graph used for association when association given a block without graph options.  The block is ignored in this case.  This will result in an exception starting in Sequel 6.  Model: #{r[:model]}, association: #{r[:name]}"
3423     end
3424   end
3425 
3426   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])
3427   if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order]))
3428     ds = ds.order_append(*qualified_expression(order, assoc_table_alias))
3429   end
3430   eager_graph = ds.opts[:eager_graph]
3431   eager_graph[:requirements][assoc_table_alias] = requirements.dup
3432   eager_graph[:reflections][assoc_table_alias] = r
3433   if limit_strategy == :ruby
3434     eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 
3435   end
3436   eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2
3437   ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty?
3438   ds
3439 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
3450 def eager_graph_associations(ds, model, ta, requirements, *associations)
3451   associations.flatten.each do |association|
3452     ds = case association
3453     when Symbol, SQL::AliasedExpression
3454       ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association))
3455     when Hash
3456       association.each do |assoc, assoc_assocs|
3457         ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs)
3458       end
3459       ds
3460     else
3461       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3462     end
3463   end
3464   ds
3465 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
3469 def eager_graph_build_associations(hashes)
3470   hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader))
3471 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
3477 def _association_join(type, associations)
3478   clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join])
3479 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
3483 def _eager_graph_build_associations(hashes, egl)
3484   egl.load(hashes)
3485 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
3490 def add_association_filter_conditions(ref, obj, expr)
3491   if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions?
3492     Sequel[ref.filter_by_associations_conditions_expression(obj)]
3493   else
3494     expr
3495   end
3496 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
3518 def association_filter_expression(op, ref, obj)
3519   meth = :"#{ref[:type]}_association_filter_expression"
3520   # Allow calling private association specific method to get filter expression
3521   send(meth, op, ref, obj) if respond_to?(meth, true)
3522 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
3526 def association_filter_handle_inversion(op, exp, cols)
3527   if op == :'!=' || op == :'NOT IN'
3528     if exp == SQL::Constants::FALSE
3529       ~exp
3530     else
3531       ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR)
3532     end
3533   else
3534     exp
3535   end
3536 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
3541 def association_filter_key_expression(keys, meths, obj)
3542   vals = if obj.is_a?(Sequel::Dataset)
3543     {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))}
3544   else
3545     vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}}
3546     return SQL::Constants::FALSE if vals.empty?
3547     if obj.is_a?(Array)
3548       if keys.length == 1
3549         meth = meths.first
3550         {keys.first=>vals.map{|o| o.get_column_value(meth)}}
3551       else
3552         {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}}
3553       end  
3554     else
3555       keys.zip(meths.map{|k| obj.get_column_value(k)})
3556     end
3557   end
3558   SQL::BooleanExpression.from_value_pairs(vals)
3559 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
3562 def check_association(model, association)
3563   raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association)
3564   raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false
3565   reflection
3566 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
3570 def eager_graph_check_association(model, association)
3571   reflection = if association.is_a?(SQL::AliasedExpression)
3572     expr = association.expression
3573     if expr.is_a?(SQL::Identifier)
3574       expr = expr.value
3575       if expr.is_a?(String)
3576         expr = expr.to_sym
3577       end
3578     end
3579 
3580     check_reflection = check_association(model, expr)
3581     SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns)
3582   else
3583     check_reflection = check_association(model, association)
3584   end
3585 
3586   if check_reflection && check_reflection[:allow_eager_graph] == false
3587     raise Error, "eager_graph not allowed for #{reflection.inspect}"
3588   end
3589 
3590   reflection
3591 end
eager_graph_loader() click to toggle source

The EagerGraphLoader instance used for converting eager_graph results.

     # File lib/sequel/model/associations.rb
3594 def eager_graph_loader
3595   unless egl = cache_get(:_model_eager_graph_loader)
3596     egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self))
3597   end
3598   egl.dup
3599 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
3602 def eager_load(a, eager_assoc=@opts[:eager], m=model)
3603   return if a.empty?
3604 
3605   # Reflections for all associations to eager load
3606   reflections = eager_assoc.keys.map{|assoc| m.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")}
3607 
3608   perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc))
3609 
3610   reflections.each do |r|
3611     a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load]
3612   end 
3613 
3614   nil
3615 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
3500 def eager_options_for_associations(associations)
3501   opts = {}
3502   associations.flatten.each do |association|
3503     case association
3504     when Symbol
3505       check_association(model, association)
3506       opts[association] = nil
3507     when Hash
3508       association.keys.each{|assoc| check_association(model, assoc)}
3509       opts.merge!(association)
3510     else
3511       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3512     end
3513   end
3514   opts
3515 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
3682 def many_to_many_association_filter_expression(op, ref, obj)
3683   lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys)
3684   jt = ref.join_table_alias
3685   lpks = lpks.first if lpks.length == 1
3686   lpks = ref.qualify(model.table_name, lpks)
3687 
3688   meths = if obj.is_a?(Sequel::Dataset)
3689     ref.qualify(obj.model.table_name, ref.right_primary_keys)
3690   else
3691     ref.right_primary_key_methods
3692   end
3693 
3694   expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj)
3695   unless expr == SQL::Constants::FALSE
3696     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)))
3697     expr = add_association_filter_conditions(ref, obj, expr)
3698   end
3699 
3700   association_filter_handle_inversion(op, expr, Array(lpks))
3701 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
3705 def many_to_one_association_filter_expression(op, ref, obj)
3706   keys = ref.qualify(model.table_name, ref[:key_columns])
3707   meths = if obj.is_a?(Sequel::Dataset)
3708     ref.qualify(obj.model.table_name, ref.primary_keys)
3709   else
3710     ref.primary_key_methods
3711   end
3712 
3713   expr = association_filter_key_expression(keys, meths, obj)
3714   expr = add_association_filter_conditions(ref, obj, expr)
3715   association_filter_handle_inversion(op, expr, keys)
3716 end
non_sql_option?(key) click to toggle source
Calls superclass method
     # File lib/sequel/model/associations.rb
3733 def non_sql_option?(key)
3734   super || key == :eager || key == :eager_graph
3735 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
3719 def one_to_many_association_filter_expression(op, ref, obj)
3720   keys = ref.qualify(model.table_name, ref[:primary_key_columns])
3721   meths = if obj.is_a?(Sequel::Dataset)
3722     ref.qualify(obj.model.table_name, ref[:keys])
3723   else
3724     ref[:key_methods]
3725   end
3726 
3727   expr = association_filter_key_expression(keys, meths, obj)
3728   expr = add_association_filter_conditions(ref, obj, expr)
3729   association_filter_handle_inversion(op, expr, keys)
3730 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
3677 def perform_eager_load(loader, eo)
3678   loader.call(eo)
3679 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
3670 def perform_eager_loads(eager_load_data)
3671   eager_load_data.map do |loader, eo|
3672     perform_eager_load(loader, eo)
3673   end
3674 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
3739 def post_load(all_records)
3740   eager_graph_build_associations(all_records) if @opts[:eager_graph]
3741   eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph])
3742   super
3743 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
3618 def prepare_eager_load(a, reflections, eager_assoc)
3619   eager_load_data = {}.compare_by_identity
3620 
3621   # Key is foreign/primary key name symbol.
3622   # Value is hash with keys being foreign/primary key values (generally integers)
3623   # and values being an array of current model objects with that specific foreign/primary key
3624   key_hash = {}
3625       
3626   # Populate the key_hash entry for each association being eagerly loaded
3627   reflections.each do |r|
3628     if key = r.eager_loader_key
3629       # key_hash for this key has already been populated,
3630       # skip populating again so that duplicate values
3631       # aren't added.
3632       unless id_map = key_hash[key]
3633         id_map = key_hash[key] = Hash.new{|h,k| h[k] = []}
3634 
3635         # Supporting both single (Symbol) and composite (Array) keys.
3636         a.each do |rec|
3637           case key
3638           when Array
3639             if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all?
3640               id_map[k] << rec
3641             end
3642           when Symbol
3643             if k = rec.get_column_value(key)
3644               id_map[k] << rec
3645             end
3646           else
3647             raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}"
3648           end
3649         end
3650       end
3651     else
3652       id_map = nil
3653     end
3654   
3655     associations = eager_assoc[r[:name]]
3656     if associations.respond_to?(:call)
3657       eager_block = associations
3658       associations = OPTS
3659     elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call)
3660       eager_block, associations = pr_assoc
3661     end
3662 
3663     eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map}
3664   end
3665 
3666   eager_load_data
3667 end