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
If the dataset is being eagerly loaded, default to calling all instead of each.
# File lib/sequel/model/associations.rb 3519 def as_hash(key_column=nil, value_column=nil, opts=OPTS) 3520 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3521 opts = Hash[opts] 3522 opts[:all] = true 3523 end 3524 super 3525 end
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 3225 def association_join(*associations) 3226 association_inner_join(*associations) 3227 end
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.
# File lib/sequel/model/associations.rb 3236 def complex_expression_sql_append(sql, op, args) 3237 r = args[1] 3238 if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) || 3239 (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)}))))) 3240 l = args[0] 3241 if ar = model.association_reflection(l) 3242 raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false 3243 3244 if multiple 3245 klass = ar.associated_class 3246 if is_ds 3247 if r.respond_to?(:model) 3248 unless r.model <= klass 3249 # A dataset for a different model class, could be a valid regular query 3250 return super 3251 end 3252 else 3253 # Not a model dataset, could be a valid regular query 3254 return super 3255 end 3256 else 3257 unless r.all?{|x| x.is_a?(klass)} 3258 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}" 3259 end 3260 end 3261 elsif !r.is_a?(ar.associated_class) 3262 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}" 3263 end 3264 3265 if exp = association_filter_expression(op, ar, r) 3266 literal_append(sql, exp) 3267 else 3268 raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}" 3269 end 3270 elsif multiple && (is_ds || r.empty?) 3271 # Not a query designed for this support, could be a valid regular query 3272 super 3273 else 3274 raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}" 3275 end 3276 else 3277 super 3278 end 3279 end
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 3356 def eager(*associations) 3357 opts = @opts[:eager] 3358 association_opts = eager_options_for_associations(associations) 3359 opts = opts ? opts.merge(association_opts) : association_opts 3360 clone(:eager=>opts.freeze) 3361 end
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 3466 def eager_graph(*associations) 3467 eager_graph_with_options(associations) 3468 end
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 3490 def eager_graph_with_options(associations, opts=OPTS) 3491 return self if associations.empty? 3492 3493 opts = opts.dup unless opts.frozen? 3494 associations = [associations] unless associations.is_a?(Array) 3495 ds = if eg = @opts[:eager_graph] 3496 eg = eg.dup 3497 [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup} 3498 eg[:local] = opts 3499 ds = clone(:eager_graph=>eg) 3500 ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations) 3501 else 3502 # Each of the following have a symbol key for the table alias, with the following values: 3503 # :reciprocals :: the reciprocal value to use for this association 3504 # :reflections :: AssociationReflection instance related to this association 3505 # :requirements :: array of requirements for this association 3506 # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading 3507 opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc} 3508 ds = clone(:eager_graph=>opts) 3509 ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked 3510 end 3511 3512 ds.opts[:eager_graph].freeze 3513 ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)} 3514 ds 3515 end
If the dataset is being eagerly loaded, default to calling all instead of each.
# File lib/sequel/model/associations.rb 3529 def to_hash_groups(key_column, value_column=nil, opts=OPTS) 3530 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3531 opts = Hash[opts] 3532 opts[:all] = true 3533 end 3534 super 3535 end
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.
# File lib/sequel/model/associations.rb 3541 def ungraphed 3542 ds = super.clone(:eager_graph=>nil) 3543 if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc]) 3544 ds = ds.with_row_proc(rp) 3545 end 3546 ds 3547 end
Protected Instance Methods
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::AliasedExpressionwith 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 3566 def eager_graph_association(ds, model, ta, requirements, r, *associations) 3567 if r.is_a?(SQL::AliasedExpression) 3568 alias_base = r.alias 3569 if r.columns.is_a?(Hash) 3570 join_type = r.columns[:join_type] 3571 end 3572 r = r.expression 3573 else 3574 alias_base = r[:graph_alias_base] 3575 end 3576 assoc_table_alias = ds.unused_table_alias(alias_base) 3577 loader = r[:eager_grapher] 3578 if !associations.empty? 3579 if associations.first.respond_to?(:call) 3580 callback = associations.first 3581 associations = {} 3582 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) 3583 callback, assoc = pr_assoc 3584 associations = assoc.is_a?(Array) ? assoc : [assoc] 3585 end 3586 end 3587 local_opts = ds.opts[:eager_graph][:local] 3588 limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy]) 3589 3590 # SEQUEL6: remove and integrate the auto_restrict_eager_graph plugin 3591 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] 3592 if r[:conditions] && !Sequel.condition_specifier?(r[:conditions]) 3593 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]}" 3594 end 3595 3596 if r[:block] && !r[:graph_use_association_block] 3597 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]}" 3598 end 3599 end 3600 3601 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]) 3602 if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order])) 3603 ds = ds.order_append(*qualified_expression(order, assoc_table_alias)) 3604 end 3605 eager_graph = ds.opts[:eager_graph] 3606 eager_graph[:requirements][assoc_table_alias] = requirements.dup 3607 eager_graph[:reflections][assoc_table_alias] = r 3608 if limit_strategy == :ruby 3609 eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 3610 end 3611 eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2 3612 ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty? 3613 ds 3614 end
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 3625 def eager_graph_associations(ds, model, ta, requirements, *associations) 3626 associations.flatten.each do |association| 3627 ds = case association 3628 when Symbol, SQL::AliasedExpression 3629 ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association)) 3630 when Hash 3631 association.each do |assoc, assoc_assocs| 3632 ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs) 3633 end 3634 ds 3635 else 3636 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3637 end 3638 end 3639 ds 3640 end
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 3644 def eager_graph_build_associations(hashes) 3645 hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader)) 3646 end
Private Instance Methods
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 3652 def _association_join(type, associations) 3653 clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join]) 3654 end
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 3658 def _eager_graph_build_associations(hashes, egl) 3659 egl.load(hashes) 3660 end
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 3665 def add_association_filter_conditions(ref, obj, expr) 3666 if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions? 3667 Sequel[ref.filter_by_associations_conditions_expression(obj)] 3668 else 3669 expr 3670 end 3671 end
Return an expression for filtering by the given association reflection and associated object.
# File lib/sequel/model/associations.rb 3693 def association_filter_expression(op, ref, obj) 3694 meth = :"#{ref[:type]}_association_filter_expression" 3695 # Allow calling private association specific method to get filter expression 3696 send(meth, op, ref, obj) if respond_to?(meth, true) 3697 end
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 3701 def association_filter_handle_inversion(op, exp, cols) 3702 if op == :'!=' || op == :'NOT IN' 3703 if exp == SQL::Constants::FALSE 3704 ~exp 3705 else 3706 ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR) 3707 end 3708 else 3709 exp 3710 end 3711 end
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 3716 def association_filter_key_expression(keys, meths, obj) 3717 vals = if obj.is_a?(Sequel::Dataset) 3718 {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))} 3719 else 3720 vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}} 3721 return SQL::Constants::FALSE if vals.empty? 3722 if obj.is_a?(Array) || obj.is_a?(Set) 3723 if keys.length == 1 3724 meth = meths.first 3725 {keys.first=>vals.map{|o| o.get_column_value(meth)}} 3726 else 3727 {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}} 3728 end 3729 else 3730 keys.zip(meths.map{|k| obj.get_column_value(k)}) 3731 end 3732 end 3733 SQL::BooleanExpression.from_value_pairs(vals) 3734 end
Make sure the association is valid for this model, and return the related AssociationReflection.
# File lib/sequel/model/associations.rb 3737 def check_association(model, association) 3738 raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association) 3739 raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false 3740 reflection 3741 end
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 3745 def eager_graph_check_association(model, association) 3746 reflection = if association.is_a?(SQL::AliasedExpression) 3747 expr = association.expression 3748 if expr.is_a?(SQL::Identifier) 3749 expr = expr.value 3750 if expr.is_a?(String) 3751 expr = expr.to_sym 3752 end 3753 end 3754 3755 check_reflection = check_association(model, expr) 3756 SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns) 3757 else 3758 check_reflection = check_association(model, association) 3759 end 3760 3761 if check_reflection && check_reflection[:allow_eager_graph] == false 3762 raise Error, "eager_graph not allowed for #{reflection.inspect}" 3763 end 3764 3765 reflection 3766 end
The EagerGraphLoader instance used for converting eager_graph results.
# File lib/sequel/model/associations.rb 3769 def eager_graph_loader 3770 unless egl = cache_get(:_model_eager_graph_loader) 3771 egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self)) 3772 end 3773 egl.dup 3774 end
Eagerly load all specified associations.
# File lib/sequel/model/associations.rb 3777 def eager_load(a, eager_assoc=@opts[:eager], m=model) 3778 return if a.empty? 3779 3780 # Reflections for all associations to eager load 3781 reflections = eager_assoc.keys.map{|assoc| m.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")} 3782 3783 perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc)) 3784 3785 reflections.each do |r| 3786 a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load] 3787 end 3788 3789 nil 3790 end
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 3675 def eager_options_for_associations(associations) 3676 opts = {} 3677 associations.flatten.each do |association| 3678 case association 3679 when Symbol 3680 check_association(model, association) 3681 opts[association] = nil 3682 when Hash 3683 association.keys.each{|assoc| check_association(model, assoc)} 3684 opts.merge!(association) 3685 else 3686 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3687 end 3688 end 3689 opts 3690 end
Return a subquery expression for filering by a many_to_many association
# File lib/sequel/model/associations.rb 3857 def many_to_many_association_filter_expression(op, ref, obj) 3858 lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys) 3859 jt = ref.join_table_alias 3860 lpks = lpks.first if lpks.length == 1 3861 lpks = ref.qualify(model.table_name, lpks) 3862 3863 meths = if obj.is_a?(Sequel::Dataset) 3864 ref.qualify(obj.model.table_name, ref.right_primary_keys) 3865 else 3866 ref.right_primary_key_methods 3867 end 3868 3869 expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj) 3870 unless expr == SQL::Constants::FALSE 3871 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))) 3872 expr = add_association_filter_conditions(ref, obj, expr) 3873 end 3874 3875 association_filter_handle_inversion(op, expr, Array(lpks)) 3876 end
Return a simple equality expression for filering by a many_to_one association
# File lib/sequel/model/associations.rb 3880 def many_to_one_association_filter_expression(op, ref, obj) 3881 keys = ref.qualify(model.table_name, ref[:key_columns]) 3882 meths = if obj.is_a?(Sequel::Dataset) 3883 ref.qualify(obj.model.table_name, ref.primary_keys) 3884 else 3885 ref.primary_key_methods 3886 end 3887 3888 expr = association_filter_key_expression(keys, meths, obj) 3889 expr = add_association_filter_conditions(ref, obj, expr) 3890 association_filter_handle_inversion(op, expr, keys) 3891 end
# File lib/sequel/model/associations.rb 3908 def non_sql_option?(key) 3909 super || key == :eager || key == :eager_graph 3910 end
Return a simple equality expression for filering by a one_to_* association
# File lib/sequel/model/associations.rb 3894 def one_to_many_association_filter_expression(op, ref, obj) 3895 keys = ref.qualify(model.table_name, ref[:primary_key_columns]) 3896 meths = if obj.is_a?(Sequel::Dataset) 3897 ref.qualify(obj.model.table_name, ref[:keys]) 3898 else 3899 ref[:key_methods] 3900 end 3901 3902 expr = association_filter_key_expression(keys, meths, obj) 3903 expr = add_association_filter_conditions(ref, obj, expr) 3904 association_filter_handle_inversion(op, expr, keys) 3905 end
Perform eager loading for a single association using the loader and eager options.
# File lib/sequel/model/associations.rb 3852 def perform_eager_load(loader, eo) 3853 loader.call(eo) 3854 end
Using the hash of loaders and eager options, perform the eager loading.
# File lib/sequel/model/associations.rb 3845 def perform_eager_loads(eager_load_data) 3846 eager_load_data.map do |loader, eo| 3847 perform_eager_load(loader, eo) 3848 end 3849 end
Build associations from the graph if eager_graph was used, and/or load other associations if eager was used.
# File lib/sequel/model/associations.rb 3914 def post_load(all_records) 3915 eager_graph_build_associations(all_records) if @opts[:eager_graph] 3916 eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph]) 3917 super 3918 end
Prepare a hash loaders and eager options which will be used to implement the eager loading.
# File lib/sequel/model/associations.rb 3793 def prepare_eager_load(a, reflections, eager_assoc) 3794 eager_load_data = {}.compare_by_identity 3795 3796 # Key is foreign/primary key name symbol. 3797 # Value is hash with keys being foreign/primary key values (generally integers) 3798 # and values being an array of current model objects with that specific foreign/primary key 3799 key_hash = {} 3800 3801 # Populate the key_hash entry for each association being eagerly loaded 3802 reflections.each do |r| 3803 if key = r.eager_loader_key 3804 # key_hash for this key has already been populated, 3805 # skip populating again so that duplicate values 3806 # aren't added. 3807 unless id_map = key_hash[key] 3808 id_map = key_hash[key] = Hash.new{|h,k| h[k] = []} 3809 3810 # Supporting both single (Symbol) and composite (Array) keys. 3811 a.each do |rec| 3812 case key 3813 when Array 3814 if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all? 3815 id_map[k] << rec 3816 end 3817 when Symbol 3818 if k = rec.get_column_value(key) 3819 id_map[k] << rec 3820 end 3821 else 3822 raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}" 3823 end 3824 end 3825 end 3826 else 3827 id_map = nil 3828 end 3829 3830 associations = eager_assoc[r[:name]] 3831 if associations.respond_to?(:call) 3832 eager_block = associations 3833 associations = OPTS 3834 elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call) 3835 eager_block, associations = pr_assoc 3836 end 3837 3838 eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map} 3839 end 3840 3841 eager_load_data 3842 end