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 3111 def as_hash(key_column=nil, value_column=nil, opts=OPTS) 3112 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3113 opts = Hash[opts] 3114 opts[:all] = true 3115 end 3116 super 3117 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 2821 def association_join(*associations) 2822 association_inner_join(*associations) 2823 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 2832 def complex_expression_sql_append(sql, op, args) 2833 r = args[1] 2834 if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) || 2835 (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)}))))) 2836 l = args[0] 2837 if ar = model.association_reflections[l] 2838 if multiple 2839 klass = ar.associated_class 2840 if is_ds 2841 if r.respond_to?(:model) 2842 unless r.model <= klass 2843 # A dataset for a different model class, could be a valid regular query 2844 return super 2845 end 2846 else 2847 # Not a model dataset, could be a valid regular query 2848 return super 2849 end 2850 else 2851 unless r.all?{|x| x.is_a?(klass)} 2852 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}" 2853 end 2854 end 2855 elsif !r.is_a?(ar.associated_class) 2856 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}" 2857 end 2858 2859 if exp = association_filter_expression(op, ar, r) 2860 literal_append(sql, exp) 2861 else 2862 raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}" 2863 end 2864 elsif multiple && (is_ds || r.empty?) 2865 # Not a query designed for this support, could be a valid regular query 2866 super 2867 else 2868 raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}" 2869 end 2870 else 2871 super 2872 end 2873 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 2950 def eager(*associations) 2951 opts = @opts[:eager] 2952 association_opts = eager_options_for_associations(associations) 2953 opts = opts ? opts.merge(association_opts) : association_opts 2954 clone(:eager=>opts.freeze) 2955 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 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.
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 3058 def eager_graph(*associations) 3059 eager_graph_with_options(associations) 3060 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 3082 def eager_graph_with_options(associations, opts=OPTS) 3083 return self if associations.empty? 3084 3085 opts = opts.dup unless opts.frozen? 3086 associations = [associations] unless associations.is_a?(Array) 3087 ds = if eg = @opts[:eager_graph] 3088 eg = eg.dup 3089 [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup} 3090 eg[:local] = opts 3091 ds = clone(:eager_graph=>eg) 3092 ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations) 3093 else 3094 # Each of the following have a symbol key for the table alias, with the following values: 3095 # :reciprocals :: the reciprocal value to use for this association 3096 # :reflections :: AssociationReflection instance related to this association 3097 # :requirements :: array of requirements for this association 3098 # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading 3099 opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc} 3100 ds = clone(:eager_graph=>opts) 3101 ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked 3102 end 3103 3104 ds.opts[:eager_graph].freeze 3105 ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)} 3106 ds 3107 end
If the dataset is being eagerly loaded, default to calling all instead of each.
# File lib/sequel/model/associations.rb 3121 def to_hash_groups(key_column, value_column=nil, opts=OPTS) 3122 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3123 opts = Hash[opts] 3124 opts[:all] = true 3125 end 3126 super 3127 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 3133 def ungraphed 3134 ds = super.clone(:eager_graph=>nil) 3135 if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc]) 3136 ds = ds.with_row_proc(rp) 3137 end 3138 ds 3139 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::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 3158 def eager_graph_association(ds, model, ta, requirements, r, *associations) 3159 if r.is_a?(SQL::AliasedExpression) 3160 alias_base = r.alias 3161 if r.columns.is_a?(Hash) 3162 join_type = r.columns[:join_type] 3163 end 3164 r = r.expression 3165 else 3166 alias_base = r[:graph_alias_base] 3167 end 3168 assoc_table_alias = ds.unused_table_alias(alias_base) 3169 loader = r[:eager_grapher] 3170 if !associations.empty? 3171 if associations.first.respond_to?(:call) 3172 callback = associations.first 3173 associations = {} 3174 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) 3175 callback, assoc = pr_assoc 3176 associations = assoc.is_a?(Array) ? assoc : [assoc] 3177 end 3178 end 3179 local_opts = ds.opts[:eager_graph][:local] 3180 limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy]) 3181 3182 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) 3183 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]}" 3184 end 3185 3186 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]) 3187 if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order])) 3188 ds = ds.order_append(*qualified_expression(order, assoc_table_alias)) 3189 end 3190 eager_graph = ds.opts[:eager_graph] 3191 eager_graph[:requirements][assoc_table_alias] = requirements.dup 3192 eager_graph[:reflections][assoc_table_alias] = r 3193 if limit_strategy == :ruby 3194 eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 3195 end 3196 eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2 3197 ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty? 3198 ds 3199 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 3210 def eager_graph_associations(ds, model, ta, requirements, *associations) 3211 associations.flatten.each do |association| 3212 ds = case association 3213 when Symbol, SQL::AliasedExpression 3214 ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association)) 3215 when Hash 3216 association.each do |assoc, assoc_assocs| 3217 ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs) 3218 end 3219 ds 3220 else 3221 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3222 end 3223 end 3224 ds 3225 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 3229 def eager_graph_build_associations(hashes) 3230 hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader)) 3231 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 3237 def _association_join(type, associations) 3238 clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join]) 3239 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 3243 def _eager_graph_build_associations(hashes, egl) 3244 egl.load(hashes) 3245 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 3250 def add_association_filter_conditions(ref, obj, expr) 3251 if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions? 3252 Sequel[ref.filter_by_associations_conditions_expression(obj)] 3253 else 3254 expr 3255 end 3256 end
Return an expression for filtering by the given association reflection and associated object.
# File lib/sequel/model/associations.rb 3278 def association_filter_expression(op, ref, obj) 3279 meth = :"#{ref[:type]}_association_filter_expression" 3280 # Allow calling private association specific method to get filter expression 3281 send(meth, op, ref, obj) if respond_to?(meth, true) 3282 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 3286 def association_filter_handle_inversion(op, exp, cols) 3287 if op == :'!=' || op == :'NOT IN' 3288 if exp == SQL::Constants::FALSE 3289 ~exp 3290 else 3291 ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR) 3292 end 3293 else 3294 exp 3295 end 3296 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 3301 def association_filter_key_expression(keys, meths, obj) 3302 vals = if obj.is_a?(Sequel::Dataset) 3303 {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))} 3304 else 3305 vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}} 3306 return SQL::Constants::FALSE if vals.empty? 3307 if obj.is_a?(Array) 3308 if keys.length == 1 3309 meth = meths.first 3310 {keys.first=>vals.map{|o| o.get_column_value(meth)}} 3311 else 3312 {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}} 3313 end 3314 else 3315 keys.zip(meths.map{|k| obj.get_column_value(k)}) 3316 end 3317 end 3318 SQL::BooleanExpression.from_value_pairs(vals) 3319 end
Make sure the association is valid for this model, and return the related AssociationReflection
.
# File lib/sequel/model/associations.rb 3322 def check_association(model, association) 3323 raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association) 3324 raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false 3325 reflection 3326 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 3330 def eager_graph_check_association(model, association) 3331 if association.is_a?(SQL::AliasedExpression) 3332 expr = association.expression 3333 if expr.is_a?(SQL::Identifier) 3334 expr = expr.value 3335 if expr.is_a?(String) 3336 expr = expr.to_sym 3337 end 3338 end 3339 3340 SQL::AliasedExpression.new(check_association(model, expr), association.alias || expr, association.columns) 3341 else 3342 check_association(model, association) 3343 end 3344 end
The EagerGraphLoader
instance used for converting eager_graph
results.
# File lib/sequel/model/associations.rb 3347 def eager_graph_loader 3348 unless egl = cache_get(:_model_eager_graph_loader) 3349 egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self)) 3350 end 3351 egl.dup 3352 end
Eagerly load all specified associations
# File lib/sequel/model/associations.rb 3355 def eager_load(a, eager_assoc=@opts[:eager]) 3356 return if a.empty? 3357 # Key is foreign/primary key name symbol. 3358 # Value is hash with keys being foreign/primary key values (generally integers) 3359 # and values being an array of current model objects with that specific foreign/primary key 3360 key_hash = {} 3361 # Reflections for all associations to eager load 3362 reflections = eager_assoc.keys.map{|assoc| model.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")} 3363 3364 # Populate the key_hash entry for each association being eagerly loaded 3365 reflections.each do |r| 3366 if key = r.eager_loader_key 3367 # key_hash for this key has already been populated, 3368 # skip populating again so that duplicate values 3369 # aren't added. 3370 unless id_map = key_hash[key] 3371 id_map = key_hash[key] = Hash.new{|h,k| h[k] = []} 3372 3373 # Supporting both single (Symbol) and composite (Array) keys. 3374 a.each do |rec| 3375 case key 3376 when Array 3377 if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all? 3378 id_map[k] << rec 3379 end 3380 when Symbol 3381 if k = rec.get_column_value(key) 3382 id_map[k] << rec 3383 end 3384 else 3385 raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}" 3386 end 3387 end 3388 end 3389 else 3390 id_map = nil 3391 end 3392 3393 loader = r[:eager_loader] 3394 associations = eager_assoc[r[:name]] 3395 if associations.respond_to?(:call) 3396 eager_block = associations 3397 associations = OPTS 3398 elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call) 3399 eager_block, associations = pr_assoc 3400 end 3401 loader.call(:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map) 3402 a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load] 3403 end 3404 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 3260 def eager_options_for_associations(associations) 3261 opts = {} 3262 associations.flatten.each do |association| 3263 case association 3264 when Symbol 3265 check_association(model, association) 3266 opts[association] = nil 3267 when Hash 3268 association.keys.each{|assoc| check_association(model, assoc)} 3269 opts.merge!(association) 3270 else 3271 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3272 end 3273 end 3274 opts 3275 end
Return a subquery expression for filering by a many_to_many association
# File lib/sequel/model/associations.rb 3407 def many_to_many_association_filter_expression(op, ref, obj) 3408 lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys) 3409 jt = ref.join_table_alias 3410 lpks = lpks.first if lpks.length == 1 3411 lpks = ref.qualify(model.table_name, lpks) 3412 3413 meths = if obj.is_a?(Sequel::Dataset) 3414 ref.qualify(obj.model.table_name, ref.right_primary_keys) 3415 else 3416 ref.right_primary_key_methods 3417 end 3418 3419 expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj) 3420 unless expr == SQL::Constants::FALSE 3421 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))) 3422 expr = add_association_filter_conditions(ref, obj, expr) 3423 end 3424 3425 association_filter_handle_inversion(op, expr, Array(lpks)) 3426 end
Return a simple equality expression for filering by a many_to_one association
# File lib/sequel/model/associations.rb 3430 def many_to_one_association_filter_expression(op, ref, obj) 3431 keys = ref.qualify(model.table_name, ref[:key_columns]) 3432 meths = if obj.is_a?(Sequel::Dataset) 3433 ref.qualify(obj.model.table_name, ref.primary_keys) 3434 else 3435 ref.primary_key_methods 3436 end 3437 3438 expr = association_filter_key_expression(keys, meths, obj) 3439 expr = add_association_filter_conditions(ref, obj, expr) 3440 association_filter_handle_inversion(op, expr, keys) 3441 end
# File lib/sequel/model/associations.rb 3458 def non_sql_option?(key) 3459 super || key == :eager || key == :eager_graph 3460 end
Return a simple equality expression for filering by a one_to_* association
# File lib/sequel/model/associations.rb 3444 def one_to_many_association_filter_expression(op, ref, obj) 3445 keys = ref.qualify(model.table_name, ref[:primary_key_columns]) 3446 meths = if obj.is_a?(Sequel::Dataset) 3447 ref.qualify(obj.model.table_name, ref[:keys]) 3448 else 3449 ref[:key_methods] 3450 end 3451 3452 expr = association_filter_key_expression(keys, meths, obj) 3453 expr = add_association_filter_conditions(ref, obj, expr) 3454 association_filter_handle_inversion(op, expr, keys) 3455 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 3464 def post_load(all_records) 3465 eager_graph_build_associations(all_records) if @opts[:eager_graph] 3466 eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph]) 3467 super 3468 end