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
Source
# File lib/sequel/model/associations.rb 3518 def as_hash(key_column=nil, value_column=nil, opts=OPTS) 3519 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3520 opts = Hash[opts] 3521 opts[:all] = true 3522 end 3523 super 3524 end
If the dataset is being eagerly loaded, default to calling all instead of each.
Source
# File lib/sequel/model/associations.rb 3224 def association_join(*associations) 3225 association_inner_join(*associations) 3226 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)
Source
# File lib/sequel/model/associations.rb 3235 def complex_expression_sql_append(sql, op, args) 3236 r = args[1] 3237 if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) || 3238 (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)}))))) 3239 l = args[0] 3240 if ar = model.association_reflection(l) 3241 raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false 3242 3243 if multiple 3244 klass = ar.associated_class 3245 if is_ds 3246 if r.respond_to?(:model) 3247 unless r.model <= klass 3248 # A dataset for a different model class, could be a valid regular query 3249 return super 3250 end 3251 else 3252 # Not a model dataset, could be a valid regular query 3253 return super 3254 end 3255 else 3256 unless r.all?{|x| x.is_a?(klass)} 3257 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}" 3258 end 3259 end 3260 elsif !r.is_a?(ar.associated_class) 3261 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}" 3262 end 3263 3264 if exp = association_filter_expression(op, ar, r) 3265 literal_append(sql, exp) 3266 else 3267 raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}" 3268 end 3269 elsif multiple && (is_ds || r.empty?) 3270 # Not a query designed for this support, could be a valid regular query 3271 super 3272 else 3273 raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}" 3274 end 3275 else 3276 super 3277 end 3278 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.
Source
# File lib/sequel/model/associations.rb 3355 def eager(*associations) 3356 opts = @opts[:eager] 3357 association_opts = eager_options_for_associations(associations) 3358 opts = opts ? opts.merge(association_opts) : association_opts 3359 clone(:eager=>opts.freeze) 3360 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 (...))
Source
# File lib/sequel/model/associations.rb 3465 def eager_graph(*associations) 3466 eager_graph_with_options(associations) 3467 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)
Source
# File lib/sequel/model/associations.rb 3489 def eager_graph_with_options(associations, opts=OPTS) 3490 return self if associations.empty? 3491 3492 opts = opts.dup unless opts.frozen? 3493 associations = [associations] unless associations.is_a?(Array) 3494 ds = if eg = @opts[:eager_graph] 3495 eg = eg.dup 3496 [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup} 3497 eg[:local] = opts 3498 ds = clone(:eager_graph=>eg) 3499 ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations) 3500 else 3501 # Each of the following have a symbol key for the table alias, with the following values: 3502 # :reciprocals :: the reciprocal value to use for this association 3503 # :reflections :: AssociationReflection instance related to this association 3504 # :requirements :: array of requirements for this association 3505 # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading 3506 opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc} 3507 ds = clone(:eager_graph=>opts) 3508 ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked 3509 end 3510 3511 ds.opts[:eager_graph].freeze 3512 ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)} 3513 ds 3514 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.
Source
# File lib/sequel/model/associations.rb 3528 def to_hash_groups(key_column, value_column=nil, opts=OPTS) 3529 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3530 opts = Hash[opts] 3531 opts[:all] = true 3532 end 3533 super 3534 end
If the dataset is being eagerly loaded, default to calling all instead of each.
Source
# File lib/sequel/model/associations.rb 3540 def ungraphed 3541 ds = super.clone(:eager_graph=>nil) 3542 if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc]) 3543 ds = ds.with_row_proc(rp) 3544 end 3545 ds 3546 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.
Protected Instance Methods
Source
# File lib/sequel/model/associations.rb 3565 def eager_graph_association(ds, model, ta, requirements, r, *associations) 3566 if r.is_a?(SQL::AliasedExpression) 3567 alias_base = r.alias 3568 if r.columns.is_a?(Hash) 3569 join_type = r.columns[:join_type] 3570 end 3571 r = r.expression 3572 else 3573 alias_base = r[:graph_alias_base] 3574 end 3575 assoc_table_alias = ds.unused_table_alias(alias_base) 3576 loader = r[:eager_grapher] 3577 if !associations.empty? 3578 if associations.first.respond_to?(:call) 3579 callback = associations.first 3580 associations = {} 3581 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) 3582 callback, assoc = pr_assoc 3583 associations = assoc.is_a?(Array) ? assoc : [assoc] 3584 end 3585 end 3586 local_opts = ds.opts[:eager_graph][:local] 3587 limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy]) 3588 3589 # SEQUEL6: remove and integrate the auto_restrict_eager_graph plugin 3590 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] 3591 if r[:conditions] && !Sequel.condition_specifier?(r[:conditions]) 3592 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]}" 3593 end 3594 3595 if r[:block] && !r[:graph_use_association_block] 3596 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]}" 3597 end 3598 end 3599 3600 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]) 3601 if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order])) 3602 ds = ds.order_append(*qualified_expression(order, assoc_table_alias)) 3603 end 3604 eager_graph = ds.opts[:eager_graph] 3605 eager_graph[:requirements][assoc_table_alias] = requirements.dup 3606 eager_graph[:reflections][assoc_table_alias] = r 3607 if limit_strategy == :ruby 3608 eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 3609 end 3610 eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2 3611 ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty? 3612 ds 3613 end
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
Source
# File lib/sequel/model/associations.rb 3624 def eager_graph_associations(ds, model, ta, requirements, *associations) 3625 associations.flatten.each do |association| 3626 ds = case association 3627 when Symbol, SQL::AliasedExpression 3628 ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association)) 3629 when Hash 3630 association.each do |assoc, assoc_assocs| 3631 ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs) 3632 end 3633 ds 3634 else 3635 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3636 end 3637 end 3638 ds 3639 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
Source
# File lib/sequel/model/associations.rb 3643 def eager_graph_build_associations(hashes) 3644 hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader)) 3645 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.
Private Instance Methods
Source
# File lib/sequel/model/associations.rb 3651 def _association_join(type, associations) 3652 clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join]) 3653 end
Return a new dataset with JOINs of the given type added, using the tables and conditions specified by the associations.
Source
# File lib/sequel/model/associations.rb 3657 def _eager_graph_build_associations(hashes, egl) 3658 egl.load(hashes) 3659 end
Process the array of hashes using the eager graph loader to return an array of model objects with the associations set.
Source
# File lib/sequel/model/associations.rb 3664 def add_association_filter_conditions(ref, obj, expr) 3665 if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions? 3666 Sequel[ref.filter_by_associations_conditions_expression(obj)] 3667 else 3668 expr 3669 end 3670 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.
Source
# File lib/sequel/model/associations.rb 3692 def association_filter_expression(op, ref, obj) 3693 meth = :"#{ref[:type]}_association_filter_expression" 3694 # Allow calling private association specific method to get filter expression 3695 send(meth, op, ref, obj) if respond_to?(meth, true) 3696 end
Return an expression for filtering by the given association reflection and associated object.
Source
# File lib/sequel/model/associations.rb 3700 def association_filter_handle_inversion(op, exp, cols) 3701 if op == :'!=' || op == :'NOT IN' 3702 if exp == SQL::Constants::FALSE 3703 ~exp 3704 else 3705 ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR) 3706 end 3707 else 3708 exp 3709 end 3710 end
Handle inversion for association filters by returning an inverted expression, plus also handling cases where the referenced columns are NULL.
Source
# File lib/sequel/model/associations.rb 3715 def association_filter_key_expression(keys, meths, obj) 3716 vals = if obj.is_a?(Sequel::Dataset) 3717 {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))} 3718 else 3719 vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}} 3720 return SQL::Constants::FALSE if vals.empty? 3721 if obj.is_a?(Array) || obj.is_a?(Set) 3722 if keys.length == 1 3723 meth = meths.first 3724 {keys.first=>vals.map{|o| o.get_column_value(meth)}} 3725 else 3726 {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}} 3727 end 3728 else 3729 keys.zip(meths.map{|k| obj.get_column_value(k)}) 3730 end 3731 end 3732 SQL::BooleanExpression.from_value_pairs(vals) 3733 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.
Source
# File lib/sequel/model/associations.rb 3736 def check_association(model, association) 3737 raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association) 3738 raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false 3739 reflection 3740 end
Make sure the association is valid for this model, and return the related AssociationReflection.
Source
# File lib/sequel/model/associations.rb 3744 def eager_graph_check_association(model, association) 3745 reflection = if association.is_a?(SQL::AliasedExpression) 3746 expr = association.expression 3747 if expr.is_a?(SQL::Identifier) 3748 expr = expr.value 3749 if expr.is_a?(String) 3750 expr = expr.to_sym 3751 end 3752 end 3753 3754 check_reflection = check_association(model, expr) 3755 SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns) 3756 else 3757 check_reflection = check_association(model, association) 3758 end 3759 3760 if check_reflection && check_reflection[:allow_eager_graph] == false 3761 raise Error, "eager_graph not allowed for #{reflection.inspect}" 3762 end 3763 3764 reflection 3765 end
Allow associations that are eagerly graphed to be specified as an SQL::AliasedExpression, for per-call determining of the alias base.
Source
# File lib/sequel/model/associations.rb 3768 def eager_graph_loader 3769 unless egl = cache_get(:_model_eager_graph_loader) 3770 egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self)) 3771 end 3772 egl.dup 3773 end
The EagerGraphLoader instance used for converting eager_graph results.
Source
# File lib/sequel/model/associations.rb 3776 def eager_load(a, eager_assoc=@opts[:eager], m=model) 3777 return if a.empty? 3778 3779 # Reflections for all associations to eager load 3780 reflections = eager_assoc.keys.map{|assoc| m.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")} 3781 3782 perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc)) 3783 3784 reflections.each do |r| 3785 a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load] 3786 end 3787 3788 nil 3789 end
Eagerly load all specified associations.
Source
# File lib/sequel/model/associations.rb 3674 def eager_options_for_associations(associations) 3675 opts = {} 3676 associations.flatten.each do |association| 3677 case association 3678 when Symbol 3679 check_association(model, association) 3680 opts[association] = nil 3681 when Hash 3682 association.keys.each{|assoc| check_association(model, assoc)} 3683 opts.merge!(association) 3684 else 3685 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3686 end 3687 end 3688 opts 3689 end
Process the array of associations arguments (Symbols, Arrays, and Hashes), and return a hash of options suitable for cascading.
Source
# File lib/sequel/model/associations.rb 3856 def many_to_many_association_filter_expression(op, ref, obj) 3857 lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys) 3858 jt = ref.join_table_alias 3859 lpks = lpks.first if lpks.length == 1 3860 lpks = ref.qualify(model.table_name, lpks) 3861 3862 meths = if obj.is_a?(Sequel::Dataset) 3863 ref.qualify(obj.model.table_name, ref.right_primary_keys) 3864 else 3865 ref.right_primary_key_methods 3866 end 3867 3868 expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj) 3869 unless expr == SQL::Constants::FALSE 3870 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))) 3871 expr = add_association_filter_conditions(ref, obj, expr) 3872 end 3873 3874 association_filter_handle_inversion(op, expr, Array(lpks)) 3875 end
Return a subquery expression for filering by a many_to_many association
Source
# File lib/sequel/model/associations.rb 3879 def many_to_one_association_filter_expression(op, ref, obj) 3880 keys = ref.qualify(model.table_name, ref[:key_columns]) 3881 meths = if obj.is_a?(Sequel::Dataset) 3882 ref.qualify(obj.model.table_name, ref.primary_keys) 3883 else 3884 ref.primary_key_methods 3885 end 3886 3887 expr = association_filter_key_expression(keys, meths, obj) 3888 expr = add_association_filter_conditions(ref, obj, expr) 3889 association_filter_handle_inversion(op, expr, keys) 3890 end
Return a simple equality expression for filering by a many_to_one association
Source
# File lib/sequel/model/associations.rb 3907 def non_sql_option?(key) 3908 super || key == :eager || key == :eager_graph 3909 end
Source
# File lib/sequel/model/associations.rb 3893 def one_to_many_association_filter_expression(op, ref, obj) 3894 keys = ref.qualify(model.table_name, ref[:primary_key_columns]) 3895 meths = if obj.is_a?(Sequel::Dataset) 3896 ref.qualify(obj.model.table_name, ref[:keys]) 3897 else 3898 ref[:key_methods] 3899 end 3900 3901 expr = association_filter_key_expression(keys, meths, obj) 3902 expr = add_association_filter_conditions(ref, obj, expr) 3903 association_filter_handle_inversion(op, expr, keys) 3904 end
Return a simple equality expression for filering by a one_to_* association
Source
# File lib/sequel/model/associations.rb 3851 def perform_eager_load(loader, eo) 3852 loader.call(eo) 3853 end
Perform eager loading for a single association using the loader and eager options.
Source
# File lib/sequel/model/associations.rb 3844 def perform_eager_loads(eager_load_data) 3845 eager_load_data.map do |loader, eo| 3846 perform_eager_load(loader, eo) 3847 end 3848 end
Using the hash of loaders and eager options, perform the eager loading.
Source
# File lib/sequel/model/associations.rb 3913 def post_load(all_records) 3914 eager_graph_build_associations(all_records) if @opts[:eager_graph] 3915 eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph]) 3916 super 3917 end
Build associations from the graph if eager_graph was used, and/or load other associations if eager was used.
Source
# File lib/sequel/model/associations.rb 3792 def prepare_eager_load(a, reflections, eager_assoc) 3793 eager_load_data = {}.compare_by_identity 3794 3795 # Key is foreign/primary key name symbol. 3796 # Value is hash with keys being foreign/primary key values (generally integers) 3797 # and values being an array of current model objects with that specific foreign/primary key 3798 key_hash = {} 3799 3800 # Populate the key_hash entry for each association being eagerly loaded 3801 reflections.each do |r| 3802 if key = r.eager_loader_key 3803 # key_hash for this key has already been populated, 3804 # skip populating again so that duplicate values 3805 # aren't added. 3806 unless id_map = key_hash[key] 3807 id_map = key_hash[key] = Hash.new{|h,k| h[k] = []} 3808 3809 # Supporting both single (Symbol) and composite (Array) keys. 3810 a.each do |rec| 3811 case key 3812 when Array 3813 if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all? 3814 id_map[k] << rec 3815 end 3816 when Symbol 3817 if k = rec.get_column_value(key) 3818 id_map[k] << rec 3819 end 3820 else 3821 raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}" 3822 end 3823 end 3824 end 3825 else 3826 id_map = nil 3827 end 3828 3829 associations = eager_assoc[r[:name]] 3830 if associations.respond_to?(:call) 3831 eager_block = associations 3832 associations = OPTS 3833 elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call) 3834 eager_block, associations = pr_assoc 3835 end 3836 3837 eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map} 3838 end 3839 3840 eager_load_data 3841 end
Prepare a hash loaders and eager options which will be used to implement the eager loading.