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
3304 def as_hash(key_column=nil, value_column=nil, opts=OPTS)
3305   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3306     opts = Hash[opts]
3307     opts[:all] = true
3308   end
3309   super
3310 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
3010 def association_join(*associations)
3011   association_inner_join(*associations)
3012 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
3021 def complex_expression_sql_append(sql, op, args)
3022   r = args[1]
3023   if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) ||
3024       (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)})))))
3025     l = args[0]
3026     if ar = model.association_reflections[l]
3027       raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false
3028 
3029       if multiple
3030         klass = ar.associated_class
3031         if is_ds
3032           if r.respond_to?(:model)
3033             unless r.model <= klass
3034               # A dataset for a different model class, could be a valid regular query
3035               return super
3036             end
3037           else
3038             # Not a model dataset, could be a valid regular query
3039             return super
3040           end
3041         else
3042           unless r.all?{|x| x.is_a?(klass)}
3043             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}"
3044           end
3045         end
3046       elsif !r.is_a?(ar.associated_class)
3047         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}"
3048       end
3049 
3050       if exp = association_filter_expression(op, ar, r)
3051         literal_append(sql, exp)
3052       else
3053         raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}"
3054       end
3055     elsif multiple && (is_ds || r.empty?)
3056       # Not a query designed for this support, could be a valid regular query
3057       super
3058     else
3059       raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}"
3060     end
3061   else
3062     super
3063   end
3064 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
3141 def eager(*associations)
3142   opts = @opts[:eager]
3143   association_opts = eager_options_for_associations(associations)
3144   opts = opts ? opts.merge(association_opts) : association_opts
3145   clone(:eager=>opts.freeze)
3146 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
3251 def eager_graph(*associations)
3252   eager_graph_with_options(associations)
3253 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
3275 def eager_graph_with_options(associations, opts=OPTS)
3276   return self if associations.empty?
3277 
3278   opts = opts.dup unless opts.frozen?
3279   associations = [associations] unless associations.is_a?(Array)
3280   ds = if eg = @opts[:eager_graph]
3281     eg = eg.dup
3282     [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup}
3283     eg[:local] = opts
3284     ds = clone(:eager_graph=>eg)
3285     ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations)
3286   else
3287     # Each of the following have a symbol key for the table alias, with the following values:
3288     # :reciprocals :: the reciprocal value to use for this association
3289     # :reflections :: AssociationReflection instance related to this association
3290     # :requirements :: array of requirements for this association
3291     # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading
3292     opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc}
3293     ds = clone(:eager_graph=>opts)
3294     ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked
3295   end
3296 
3297   ds.opts[:eager_graph].freeze
3298   ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)}
3299   ds
3300 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
3314 def to_hash_groups(key_column, value_column=nil, opts=OPTS)
3315   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3316     opts = Hash[opts]
3317     opts[:all] = true
3318   end
3319   super
3320 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
3326 def ungraphed
3327   ds = super.clone(:eager_graph=>nil)
3328   if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc])
3329     ds = ds.with_row_proc(rp)
3330   end
3331   ds
3332 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
3351 def eager_graph_association(ds, model, ta, requirements, r, *associations)
3352   if r.is_a?(SQL::AliasedExpression)
3353     alias_base = r.alias
3354     if r.columns.is_a?(Hash)
3355       join_type = r.columns[:join_type]
3356     end
3357     r = r.expression
3358   else
3359     alias_base = r[:graph_alias_base]
3360   end
3361   assoc_table_alias = ds.unused_table_alias(alias_base)
3362   loader = r[:eager_grapher]
3363   if !associations.empty?
3364     if associations.first.respond_to?(:call)
3365       callback = associations.first
3366       associations = {}
3367     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)
3368       callback, assoc = pr_assoc
3369       associations = assoc.is_a?(Array) ? assoc : [assoc]
3370     end
3371   end
3372   local_opts = ds.opts[:eager_graph][:local]
3373   limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy])
3374 
3375   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)
3376     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]}"
3377   end
3378 
3379   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])
3380   if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order]))
3381     ds = ds.order_append(*qualified_expression(order, assoc_table_alias))
3382   end
3383   eager_graph = ds.opts[:eager_graph]
3384   eager_graph[:requirements][assoc_table_alias] = requirements.dup
3385   eager_graph[:reflections][assoc_table_alias] = r
3386   if limit_strategy == :ruby
3387     eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 
3388   end
3389   eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2
3390   ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty?
3391   ds
3392 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
3403 def eager_graph_associations(ds, model, ta, requirements, *associations)
3404   associations.flatten.each do |association|
3405     ds = case association
3406     when Symbol, SQL::AliasedExpression
3407       ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association))
3408     when Hash
3409       association.each do |assoc, assoc_assocs|
3410         ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs)
3411       end
3412       ds
3413     else
3414       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3415     end
3416   end
3417   ds
3418 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
3422 def eager_graph_build_associations(hashes)
3423   hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader))
3424 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
3430 def _association_join(type, associations)
3431   clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join])
3432 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
3436 def _eager_graph_build_associations(hashes, egl)
3437   egl.load(hashes)
3438 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
3443 def add_association_filter_conditions(ref, obj, expr)
3444   if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions?
3445     Sequel[ref.filter_by_associations_conditions_expression(obj)]
3446   else
3447     expr
3448   end
3449 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
3471 def association_filter_expression(op, ref, obj)
3472   meth = :"#{ref[:type]}_association_filter_expression"
3473   # Allow calling private association specific method to get filter expression
3474   send(meth, op, ref, obj) if respond_to?(meth, true)
3475 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
3479 def association_filter_handle_inversion(op, exp, cols)
3480   if op == :'!=' || op == :'NOT IN'
3481     if exp == SQL::Constants::FALSE
3482       ~exp
3483     else
3484       ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR)
3485     end
3486   else
3487     exp
3488   end
3489 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
3494 def association_filter_key_expression(keys, meths, obj)
3495   vals = if obj.is_a?(Sequel::Dataset)
3496     {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))}
3497   else
3498     vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}}
3499     return SQL::Constants::FALSE if vals.empty?
3500     if obj.is_a?(Array)
3501       if keys.length == 1
3502         meth = meths.first
3503         {keys.first=>vals.map{|o| o.get_column_value(meth)}}
3504       else
3505         {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}}
3506       end  
3507     else
3508       keys.zip(meths.map{|k| obj.get_column_value(k)})
3509     end
3510   end
3511   SQL::BooleanExpression.from_value_pairs(vals)
3512 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
3515 def check_association(model, association)
3516   raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association)
3517   raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false
3518   reflection
3519 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
3523 def eager_graph_check_association(model, association)
3524   reflection = if association.is_a?(SQL::AliasedExpression)
3525     expr = association.expression
3526     if expr.is_a?(SQL::Identifier)
3527       expr = expr.value
3528       if expr.is_a?(String)
3529         expr = expr.to_sym
3530       end
3531     end
3532 
3533     check_reflection = check_association(model, expr)
3534     SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns)
3535   else
3536     check_reflection = check_association(model, association)
3537   end
3538 
3539   if check_reflection && check_reflection[:allow_eager_graph] == false
3540     raise Error, "eager_graph not allowed for #{reflection.inspect}"
3541   end
3542 
3543   reflection
3544 end
eager_graph_loader() click to toggle source

The EagerGraphLoader instance used for converting eager_graph results.

     # File lib/sequel/model/associations.rb
3547 def eager_graph_loader
3548   unless egl = cache_get(:_model_eager_graph_loader)
3549     egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self))
3550   end
3551   egl.dup
3552 end
eager_load(a, eager_assoc=@opts[:eager]) click to toggle source

Eagerly load all specified associations.

     # File lib/sequel/model/associations.rb
3555 def eager_load(a, eager_assoc=@opts[:eager])
3556   return if a.empty?
3557 
3558   # Reflections for all associations to eager load
3559   reflections = eager_assoc.keys.map{|assoc| model.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")}
3560 
3561   perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc))
3562 
3563   reflections.each do |r|
3564     a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load]
3565   end 
3566 
3567   nil
3568 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
3453 def eager_options_for_associations(associations)
3454   opts = {}
3455   associations.flatten.each do |association|
3456     case association
3457     when Symbol
3458       check_association(model, association)
3459       opts[association] = nil
3460     when Hash
3461       association.keys.each{|assoc| check_association(model, assoc)}
3462       opts.merge!(association)
3463     else
3464       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3465     end
3466   end
3467   opts
3468 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
3635 def many_to_many_association_filter_expression(op, ref, obj)
3636   lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys)
3637   jt = ref.join_table_alias
3638   lpks = lpks.first if lpks.length == 1
3639   lpks = ref.qualify(model.table_name, lpks)
3640 
3641   meths = if obj.is_a?(Sequel::Dataset)
3642     ref.qualify(obj.model.table_name, ref.right_primary_keys)
3643   else
3644     ref.right_primary_key_methods
3645   end
3646 
3647   expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj)
3648   unless expr == SQL::Constants::FALSE
3649     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)))
3650     expr = add_association_filter_conditions(ref, obj, expr)
3651   end
3652 
3653   association_filter_handle_inversion(op, expr, Array(lpks))
3654 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
3658 def many_to_one_association_filter_expression(op, ref, obj)
3659   keys = ref.qualify(model.table_name, ref[:key_columns])
3660   meths = if obj.is_a?(Sequel::Dataset)
3661     ref.qualify(obj.model.table_name, ref.primary_keys)
3662   else
3663     ref.primary_key_methods
3664   end
3665 
3666   expr = association_filter_key_expression(keys, meths, obj)
3667   expr = add_association_filter_conditions(ref, obj, expr)
3668   association_filter_handle_inversion(op, expr, keys)
3669 end
non_sql_option?(key) click to toggle source
Calls superclass method
     # File lib/sequel/model/associations.rb
3686 def non_sql_option?(key)
3687   super || key == :eager || key == :eager_graph
3688 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
3672 def one_to_many_association_filter_expression(op, ref, obj)
3673   keys = ref.qualify(model.table_name, ref[:primary_key_columns])
3674   meths = if obj.is_a?(Sequel::Dataset)
3675     ref.qualify(obj.model.table_name, ref[:keys])
3676   else
3677     ref[:key_methods]
3678   end
3679 
3680   expr = association_filter_key_expression(keys, meths, obj)
3681   expr = add_association_filter_conditions(ref, obj, expr)
3682   association_filter_handle_inversion(op, expr, keys)
3683 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
3630 def perform_eager_load(loader, eo)
3631   loader.call(eo)
3632 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
3623 def perform_eager_loads(eager_load_data)
3624   eager_load_data.map do |loader, eo|
3625     perform_eager_load(loader, eo)
3626   end
3627 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
3692 def post_load(all_records)
3693   eager_graph_build_associations(all_records) if @opts[:eager_graph]
3694   eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph])
3695   super
3696 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
3571 def prepare_eager_load(a, reflections, eager_assoc)
3572   eager_load_data = {}
3573 
3574   # Key is foreign/primary key name symbol.
3575   # Value is hash with keys being foreign/primary key values (generally integers)
3576   # and values being an array of current model objects with that specific foreign/primary key
3577   key_hash = {}
3578       
3579   # Populate the key_hash entry for each association being eagerly loaded
3580   reflections.each do |r|
3581     if key = r.eager_loader_key
3582       # key_hash for this key has already been populated,
3583       # skip populating again so that duplicate values
3584       # aren't added.
3585       unless id_map = key_hash[key]
3586         id_map = key_hash[key] = Hash.new{|h,k| h[k] = []}
3587 
3588         # Supporting both single (Symbol) and composite (Array) keys.
3589         a.each do |rec|
3590           case key
3591           when Array
3592             if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all?
3593               id_map[k] << rec
3594             end
3595           when Symbol
3596             if k = rec.get_column_value(key)
3597               id_map[k] << rec
3598             end
3599           else
3600             raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}"
3601           end
3602         end
3603       end
3604     else
3605       id_map = nil
3606     end
3607   
3608     associations = eager_assoc[r[:name]]
3609     if associations.respond_to?(:call)
3610       eager_block = associations
3611       associations = OPTS
3612     elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call)
3613       eager_block, associations = pr_assoc
3614     end
3615 
3616     eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map}
3617   end
3618 
3619   eager_load_data
3620 end