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
3285 def as_hash(key_column=nil, value_column=nil, opts=OPTS)
3286   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3287     opts = Hash[opts]
3288     opts[:all] = true
3289   end
3290   super
3291 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
2991 def association_join(*associations)
2992   association_inner_join(*associations)
2993 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
3002 def complex_expression_sql_append(sql, op, args)
3003   r = args[1]
3004   if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) ||
3005       (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)})))))
3006     l = args[0]
3007     if ar = model.association_reflections[l]
3008       raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false
3009 
3010       if multiple
3011         klass = ar.associated_class
3012         if is_ds
3013           if r.respond_to?(:model)
3014             unless r.model <= klass
3015               # A dataset for a different model class, could be a valid regular query
3016               return super
3017             end
3018           else
3019             # Not a model dataset, could be a valid regular query
3020             return super
3021           end
3022         else
3023           unless r.all?{|x| x.is_a?(klass)}
3024             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}"
3025           end
3026         end
3027       elsif !r.is_a?(ar.associated_class)
3028         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}"
3029       end
3030 
3031       if exp = association_filter_expression(op, ar, r)
3032         literal_append(sql, exp)
3033       else
3034         raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}"
3035       end
3036     elsif multiple && (is_ds || r.empty?)
3037       # Not a query designed for this support, could be a valid regular query
3038       super
3039     else
3040       raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}"
3041     end
3042   else
3043     super
3044   end
3045 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
3122 def eager(*associations)
3123   opts = @opts[:eager]
3124   association_opts = eager_options_for_associations(associations)
3125   opts = opts ? opts.merge(association_opts) : association_opts
3126   clone(:eager=>opts.freeze)
3127 end
eager_graph(*associations) click to toggle source

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

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

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

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

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

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

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

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

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
3232 def eager_graph(*associations)
3233   eager_graph_with_options(associations)
3234 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
3256 def eager_graph_with_options(associations, opts=OPTS)
3257   return self if associations.empty?
3258 
3259   opts = opts.dup unless opts.frozen?
3260   associations = [associations] unless associations.is_a?(Array)
3261   ds = if eg = @opts[:eager_graph]
3262     eg = eg.dup
3263     [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup}
3264     eg[:local] = opts
3265     ds = clone(:eager_graph=>eg)
3266     ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations)
3267   else
3268     # Each of the following have a symbol key for the table alias, with the following values:
3269     # :reciprocals :: the reciprocal value to use for this association
3270     # :reflections :: AssociationReflection instance related to this association
3271     # :requirements :: array of requirements for this association
3272     # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading
3273     opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc}
3274     ds = clone(:eager_graph=>opts)
3275     ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked
3276   end
3277 
3278   ds.opts[:eager_graph].freeze
3279   ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)}
3280   ds
3281 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
3295 def to_hash_groups(key_column, value_column=nil, opts=OPTS)
3296   if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all)
3297     opts = Hash[opts]
3298     opts[:all] = true
3299   end
3300   super
3301 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
3307 def ungraphed
3308   ds = super.clone(:eager_graph=>nil)
3309   if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc])
3310     ds = ds.with_row_proc(rp)
3311   end
3312   ds
3313 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
3332 def eager_graph_association(ds, model, ta, requirements, r, *associations)
3333   if r.is_a?(SQL::AliasedExpression)
3334     alias_base = r.alias
3335     if r.columns.is_a?(Hash)
3336       join_type = r.columns[:join_type]
3337     end
3338     r = r.expression
3339   else
3340     alias_base = r[:graph_alias_base]
3341   end
3342   assoc_table_alias = ds.unused_table_alias(alias_base)
3343   loader = r[:eager_grapher]
3344   if !associations.empty?
3345     if associations.first.respond_to?(:call)
3346       callback = associations.first
3347       associations = {}
3348     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)
3349       callback, assoc = pr_assoc
3350       associations = assoc.is_a?(Array) ? assoc : [assoc]
3351     end
3352   end
3353   local_opts = ds.opts[:eager_graph][:local]
3354   limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy])
3355 
3356   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)
3357     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]}"
3358   end
3359 
3360   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])
3361   if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order]))
3362     ds = ds.order_append(*qualified_expression(order, assoc_table_alias))
3363   end
3364   eager_graph = ds.opts[:eager_graph]
3365   eager_graph[:requirements][assoc_table_alias] = requirements.dup
3366   eager_graph[:reflections][assoc_table_alias] = r
3367   if limit_strategy == :ruby
3368     eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 
3369   end
3370   eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2
3371   ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty?
3372   ds
3373 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
3384 def eager_graph_associations(ds, model, ta, requirements, *associations)
3385   associations.flatten.each do |association|
3386     ds = case association
3387     when Symbol, SQL::AliasedExpression
3388       ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association))
3389     when Hash
3390       association.each do |assoc, assoc_assocs|
3391         ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs)
3392       end
3393       ds
3394     else
3395       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3396     end
3397   end
3398   ds
3399 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
3403 def eager_graph_build_associations(hashes)
3404   hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader))
3405 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
3411 def _association_join(type, associations)
3412   clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join])
3413 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
3417 def _eager_graph_build_associations(hashes, egl)
3418   egl.load(hashes)
3419 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
3424 def add_association_filter_conditions(ref, obj, expr)
3425   if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions?
3426     Sequel[ref.filter_by_associations_conditions_expression(obj)]
3427   else
3428     expr
3429   end
3430 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
3452 def association_filter_expression(op, ref, obj)
3453   meth = :"#{ref[:type]}_association_filter_expression"
3454   # Allow calling private association specific method to get filter expression
3455   send(meth, op, ref, obj) if respond_to?(meth, true)
3456 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
3460 def association_filter_handle_inversion(op, exp, cols)
3461   if op == :'!=' || op == :'NOT IN'
3462     if exp == SQL::Constants::FALSE
3463       ~exp
3464     else
3465       ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR)
3466     end
3467   else
3468     exp
3469   end
3470 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
3475 def association_filter_key_expression(keys, meths, obj)
3476   vals = if obj.is_a?(Sequel::Dataset)
3477     {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))}
3478   else
3479     vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}}
3480     return SQL::Constants::FALSE if vals.empty?
3481     if obj.is_a?(Array)
3482       if keys.length == 1
3483         meth = meths.first
3484         {keys.first=>vals.map{|o| o.get_column_value(meth)}}
3485       else
3486         {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}}
3487       end  
3488     else
3489       keys.zip(meths.map{|k| obj.get_column_value(k)})
3490     end
3491   end
3492   SQL::BooleanExpression.from_value_pairs(vals)
3493 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
3496 def check_association(model, association)
3497   raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association)
3498   raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false
3499   reflection
3500 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
3504 def eager_graph_check_association(model, association)
3505   reflection = if association.is_a?(SQL::AliasedExpression)
3506     expr = association.expression
3507     if expr.is_a?(SQL::Identifier)
3508       expr = expr.value
3509       if expr.is_a?(String)
3510         expr = expr.to_sym
3511       end
3512     end
3513 
3514     check_reflection = check_association(model, expr)
3515     SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns)
3516   else
3517     check_reflection = check_association(model, association)
3518   end
3519 
3520   if check_reflection && check_reflection[:allow_eager_graph] == false
3521     raise Error, "eager_graph not allowed for #{reflection.inspect}"
3522   end
3523 
3524   reflection
3525 end
eager_graph_loader() click to toggle source

The EagerGraphLoader instance used for converting eager_graph results.

     # File lib/sequel/model/associations.rb
3528 def eager_graph_loader
3529   unless egl = cache_get(:_model_eager_graph_loader)
3530     egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self))
3531   end
3532   egl.dup
3533 end
eager_load(a, eager_assoc=@opts[:eager]) click to toggle source

Eagerly load all specified associations.

     # File lib/sequel/model/associations.rb
3536 def eager_load(a, eager_assoc=@opts[:eager])
3537   return if a.empty?
3538 
3539   # Reflections for all associations to eager load
3540   reflections = eager_assoc.keys.map{|assoc| model.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")}
3541 
3542   perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc))
3543 
3544   reflections.each do |r|
3545     a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load]
3546   end 
3547 
3548   nil
3549 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
3434 def eager_options_for_associations(associations)
3435   opts = {}
3436   associations.flatten.each do |association|
3437     case association
3438     when Symbol
3439       check_association(model, association)
3440       opts[association] = nil
3441     when Hash
3442       association.keys.each{|assoc| check_association(model, assoc)}
3443       opts.merge!(association)
3444     else
3445       raise(Sequel::Error, 'Associations must be in the form of a symbol or hash')
3446     end
3447   end
3448   opts
3449 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
3616 def many_to_many_association_filter_expression(op, ref, obj)
3617   lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys)
3618   jt = ref.join_table_alias
3619   lpks = lpks.first if lpks.length == 1
3620   lpks = ref.qualify(model.table_name, lpks)
3621 
3622   meths = if obj.is_a?(Sequel::Dataset)
3623     ref.qualify(obj.model.table_name, ref.right_primary_keys)
3624   else
3625     ref.right_primary_key_methods
3626   end
3627 
3628   expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj)
3629   unless expr == SQL::Constants::FALSE
3630     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)))
3631     expr = add_association_filter_conditions(ref, obj, expr)
3632   end
3633 
3634   association_filter_handle_inversion(op, expr, Array(lpks))
3635 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
3639 def many_to_one_association_filter_expression(op, ref, obj)
3640   keys = ref.qualify(model.table_name, ref[:key_columns])
3641   meths = if obj.is_a?(Sequel::Dataset)
3642     ref.qualify(obj.model.table_name, ref.primary_keys)
3643   else
3644     ref.primary_key_methods
3645   end
3646 
3647   expr = association_filter_key_expression(keys, meths, obj)
3648   expr = add_association_filter_conditions(ref, obj, expr)
3649   association_filter_handle_inversion(op, expr, keys)
3650 end
non_sql_option?(key) click to toggle source
Calls superclass method
     # File lib/sequel/model/associations.rb
3667 def non_sql_option?(key)
3668   super || key == :eager || key == :eager_graph
3669 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
3653 def one_to_many_association_filter_expression(op, ref, obj)
3654   keys = ref.qualify(model.table_name, ref[:primary_key_columns])
3655   meths = if obj.is_a?(Sequel::Dataset)
3656     ref.qualify(obj.model.table_name, ref[:keys])
3657   else
3658     ref[:key_methods]
3659   end
3660 
3661   expr = association_filter_key_expression(keys, meths, obj)
3662   expr = add_association_filter_conditions(ref, obj, expr)
3663   association_filter_handle_inversion(op, expr, keys)
3664 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
3611 def perform_eager_load(loader, eo)
3612   loader.call(eo)
3613 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
3604 def perform_eager_loads(eager_load_data)
3605   eager_load_data.map do |loader, eo|
3606     perform_eager_load(loader, eo)
3607   end
3608 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
3673 def post_load(all_records)
3674   eager_graph_build_associations(all_records) if @opts[:eager_graph]
3675   eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph])
3676   super
3677 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
3552 def prepare_eager_load(a, reflections, eager_assoc)
3553   eager_load_data = {}
3554 
3555   # Key is foreign/primary key name symbol.
3556   # Value is hash with keys being foreign/primary key values (generally integers)
3557   # and values being an array of current model objects with that specific foreign/primary key
3558   key_hash = {}
3559       
3560   # Populate the key_hash entry for each association being eagerly loaded
3561   reflections.each do |r|
3562     if key = r.eager_loader_key
3563       # key_hash for this key has already been populated,
3564       # skip populating again so that duplicate values
3565       # aren't added.
3566       unless id_map = key_hash[key]
3567         id_map = key_hash[key] = Hash.new{|h,k| h[k] = []}
3568 
3569         # Supporting both single (Symbol) and composite (Array) keys.
3570         a.each do |rec|
3571           case key
3572           when Array
3573             if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all?
3574               id_map[k] << rec
3575             end
3576           when Symbol
3577             if k = rec.get_column_value(key)
3578               id_map[k] << rec
3579             end
3580           else
3581             raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}"
3582           end
3583         end
3584       end
3585     else
3586       id_map = nil
3587     end
3588   
3589     associations = eager_assoc[r[:name]]
3590     if associations.respond_to?(:call)
3591       eager_block = associations
3592       associations = OPTS
3593     elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call)
3594       eager_block, associations = pr_assoc
3595     end
3596 
3597     eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map}
3598   end
3599 
3600   eager_load_data
3601 end