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 3134 def as_hash(key_column=nil, value_column=nil, opts=OPTS) 3135 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3136 opts = Hash[opts] 3137 opts[:all] = true 3138 end 3139 super 3140 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 2844 def association_join(*associations) 2845 association_inner_join(*associations) 2846 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 2855 def complex_expression_sql_append(sql, op, args) 2856 r = args[1] 2857 if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) || 2858 (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)}))))) 2859 l = args[0] 2860 if ar = model.association_reflections[l] 2861 if multiple 2862 klass = ar.associated_class 2863 if is_ds 2864 if r.respond_to?(:model) 2865 unless r.model <= klass 2866 # A dataset for a different model class, could be a valid regular query 2867 return super 2868 end 2869 else 2870 # Not a model dataset, could be a valid regular query 2871 return super 2872 end 2873 else 2874 unless r.all?{|x| x.is_a?(klass)} 2875 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}" 2876 end 2877 end 2878 elsif !r.is_a?(ar.associated_class) 2879 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}" 2880 end 2881 2882 if exp = association_filter_expression(op, ar, r) 2883 literal_append(sql, exp) 2884 else 2885 raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}" 2886 end 2887 elsif multiple && (is_ds || r.empty?) 2888 # Not a query designed for this support, could be a valid regular query 2889 super 2890 else 2891 raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}" 2892 end 2893 else 2894 super 2895 end 2896 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 2973 def eager(*associations) 2974 opts = @opts[:eager] 2975 association_opts = eager_options_for_associations(associations) 2976 opts = opts ? opts.merge(association_opts) : association_opts 2977 clone(:eager=>opts.freeze) 2978 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 3081 def eager_graph(*associations) 3082 eager_graph_with_options(associations) 3083 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 3105 def eager_graph_with_options(associations, opts=OPTS) 3106 return self if associations.empty? 3107 3108 opts = opts.dup unless opts.frozen? 3109 associations = [associations] unless associations.is_a?(Array) 3110 ds = if eg = @opts[:eager_graph] 3111 eg = eg.dup 3112 [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup} 3113 eg[:local] = opts 3114 ds = clone(:eager_graph=>eg) 3115 ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations) 3116 else 3117 # Each of the following have a symbol key for the table alias, with the following values: 3118 # :reciprocals :: the reciprocal value to use for this association 3119 # :reflections :: AssociationReflection instance related to this association 3120 # :requirements :: array of requirements for this association 3121 # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading 3122 opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc} 3123 ds = clone(:eager_graph=>opts) 3124 ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked 3125 end 3126 3127 ds.opts[:eager_graph].freeze 3128 ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)} 3129 ds 3130 end
If the dataset is being eagerly loaded, default to calling all instead of each.
# File lib/sequel/model/associations.rb 3144 def to_hash_groups(key_column, value_column=nil, opts=OPTS) 3145 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3146 opts = Hash[opts] 3147 opts[:all] = true 3148 end 3149 super 3150 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 3156 def ungraphed 3157 ds = super.clone(:eager_graph=>nil) 3158 if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc]) 3159 ds = ds.with_row_proc(rp) 3160 end 3161 ds 3162 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 3181 def eager_graph_association(ds, model, ta, requirements, r, *associations) 3182 if r.is_a?(SQL::AliasedExpression) 3183 alias_base = r.alias 3184 if r.columns.is_a?(Hash) 3185 join_type = r.columns[:join_type] 3186 end 3187 r = r.expression 3188 else 3189 alias_base = r[:graph_alias_base] 3190 end 3191 assoc_table_alias = ds.unused_table_alias(alias_base) 3192 loader = r[:eager_grapher] 3193 if !associations.empty? 3194 if associations.first.respond_to?(:call) 3195 callback = associations.first 3196 associations = {} 3197 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) 3198 callback, assoc = pr_assoc 3199 associations = assoc.is_a?(Array) ? assoc : [assoc] 3200 end 3201 end 3202 local_opts = ds.opts[:eager_graph][:local] 3203 limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy]) 3204 3205 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) 3206 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]}" 3207 end 3208 3209 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]) 3210 if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order])) 3211 ds = ds.order_append(*qualified_expression(order, assoc_table_alias)) 3212 end 3213 eager_graph = ds.opts[:eager_graph] 3214 eager_graph[:requirements][assoc_table_alias] = requirements.dup 3215 eager_graph[:reflections][assoc_table_alias] = r 3216 if limit_strategy == :ruby 3217 eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 3218 end 3219 eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2 3220 ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty? 3221 ds 3222 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 3233 def eager_graph_associations(ds, model, ta, requirements, *associations) 3234 associations.flatten.each do |association| 3235 ds = case association 3236 when Symbol, SQL::AliasedExpression 3237 ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association)) 3238 when Hash 3239 association.each do |assoc, assoc_assocs| 3240 ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs) 3241 end 3242 ds 3243 else 3244 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3245 end 3246 end 3247 ds 3248 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 3252 def eager_graph_build_associations(hashes) 3253 hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader)) 3254 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 3260 def _association_join(type, associations) 3261 clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join]) 3262 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 3266 def _eager_graph_build_associations(hashes, egl) 3267 egl.load(hashes) 3268 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 3273 def add_association_filter_conditions(ref, obj, expr) 3274 if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions? 3275 Sequel[ref.filter_by_associations_conditions_expression(obj)] 3276 else 3277 expr 3278 end 3279 end
Return an expression for filtering by the given association reflection and associated object.
# File lib/sequel/model/associations.rb 3301 def association_filter_expression(op, ref, obj) 3302 meth = :"#{ref[:type]}_association_filter_expression" 3303 # Allow calling private association specific method to get filter expression 3304 send(meth, op, ref, obj) if respond_to?(meth, true) 3305 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 3309 def association_filter_handle_inversion(op, exp, cols) 3310 if op == :'!=' || op == :'NOT IN' 3311 if exp == SQL::Constants::FALSE 3312 ~exp 3313 else 3314 ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR) 3315 end 3316 else 3317 exp 3318 end 3319 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 3324 def association_filter_key_expression(keys, meths, obj) 3325 vals = if obj.is_a?(Sequel::Dataset) 3326 {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))} 3327 else 3328 vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}} 3329 return SQL::Constants::FALSE if vals.empty? 3330 if obj.is_a?(Array) 3331 if keys.length == 1 3332 meth = meths.first 3333 {keys.first=>vals.map{|o| o.get_column_value(meth)}} 3334 else 3335 {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}} 3336 end 3337 else 3338 keys.zip(meths.map{|k| obj.get_column_value(k)}) 3339 end 3340 end 3341 SQL::BooleanExpression.from_value_pairs(vals) 3342 end
Make sure the association is valid for this model, and return the related AssociationReflection
.
# File lib/sequel/model/associations.rb 3345 def check_association(model, association) 3346 raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association) 3347 raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false 3348 reflection 3349 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 3353 def eager_graph_check_association(model, association) 3354 if association.is_a?(SQL::AliasedExpression) 3355 expr = association.expression 3356 if expr.is_a?(SQL::Identifier) 3357 expr = expr.value 3358 if expr.is_a?(String) 3359 expr = expr.to_sym 3360 end 3361 end 3362 3363 SQL::AliasedExpression.new(check_association(model, expr), association.alias || expr, association.columns) 3364 else 3365 check_association(model, association) 3366 end 3367 end
The EagerGraphLoader
instance used for converting eager_graph
results.
# File lib/sequel/model/associations.rb 3370 def eager_graph_loader 3371 unless egl = cache_get(:_model_eager_graph_loader) 3372 egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self)) 3373 end 3374 egl.dup 3375 end
Eagerly load all specified associations
# File lib/sequel/model/associations.rb 3378 def eager_load(a, eager_assoc=@opts[:eager]) 3379 return if a.empty? 3380 # Key is foreign/primary key name symbol. 3381 # Value is hash with keys being foreign/primary key values (generally integers) 3382 # and values being an array of current model objects with that specific foreign/primary key 3383 key_hash = {} 3384 # Reflections for all associations to eager load 3385 reflections = eager_assoc.keys.map{|assoc| model.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")} 3386 3387 # Populate the key_hash entry for each association being eagerly loaded 3388 reflections.each do |r| 3389 if key = r.eager_loader_key 3390 # key_hash for this key has already been populated, 3391 # skip populating again so that duplicate values 3392 # aren't added. 3393 unless id_map = key_hash[key] 3394 id_map = key_hash[key] = Hash.new{|h,k| h[k] = []} 3395 3396 # Supporting both single (Symbol) and composite (Array) keys. 3397 a.each do |rec| 3398 case key 3399 when Array 3400 if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all? 3401 id_map[k] << rec 3402 end 3403 when Symbol 3404 if k = rec.get_column_value(key) 3405 id_map[k] << rec 3406 end 3407 else 3408 raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}" 3409 end 3410 end 3411 end 3412 else 3413 id_map = nil 3414 end 3415 3416 loader = r[:eager_loader] 3417 associations = eager_assoc[r[:name]] 3418 if associations.respond_to?(:call) 3419 eager_block = associations 3420 associations = OPTS 3421 elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call) 3422 eager_block, associations = pr_assoc 3423 end 3424 loader.call(:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map) 3425 a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load] 3426 end 3427 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 3283 def eager_options_for_associations(associations) 3284 opts = {} 3285 associations.flatten.each do |association| 3286 case association 3287 when Symbol 3288 check_association(model, association) 3289 opts[association] = nil 3290 when Hash 3291 association.keys.each{|assoc| check_association(model, assoc)} 3292 opts.merge!(association) 3293 else 3294 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3295 end 3296 end 3297 opts 3298 end
Return a subquery expression for filering by a many_to_many association
# File lib/sequel/model/associations.rb 3430 def many_to_many_association_filter_expression(op, ref, obj) 3431 lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys) 3432 jt = ref.join_table_alias 3433 lpks = lpks.first if lpks.length == 1 3434 lpks = ref.qualify(model.table_name, lpks) 3435 3436 meths = if obj.is_a?(Sequel::Dataset) 3437 ref.qualify(obj.model.table_name, ref.right_primary_keys) 3438 else 3439 ref.right_primary_key_methods 3440 end 3441 3442 expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj) 3443 unless expr == SQL::Constants::FALSE 3444 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))) 3445 expr = add_association_filter_conditions(ref, obj, expr) 3446 end 3447 3448 association_filter_handle_inversion(op, expr, Array(lpks)) 3449 end
Return a simple equality expression for filering by a many_to_one association
# File lib/sequel/model/associations.rb 3453 def many_to_one_association_filter_expression(op, ref, obj) 3454 keys = ref.qualify(model.table_name, ref[:key_columns]) 3455 meths = if obj.is_a?(Sequel::Dataset) 3456 ref.qualify(obj.model.table_name, ref.primary_keys) 3457 else 3458 ref.primary_key_methods 3459 end 3460 3461 expr = association_filter_key_expression(keys, meths, obj) 3462 expr = add_association_filter_conditions(ref, obj, expr) 3463 association_filter_handle_inversion(op, expr, keys) 3464 end
# File lib/sequel/model/associations.rb 3481 def non_sql_option?(key) 3482 super || key == :eager || key == :eager_graph 3483 end
Return a simple equality expression for filering by a one_to_* association
# File lib/sequel/model/associations.rb 3467 def one_to_many_association_filter_expression(op, ref, obj) 3468 keys = ref.qualify(model.table_name, ref[:primary_key_columns]) 3469 meths = if obj.is_a?(Sequel::Dataset) 3470 ref.qualify(obj.model.table_name, ref[:keys]) 3471 else 3472 ref[:key_methods] 3473 end 3474 3475 expr = association_filter_key_expression(keys, meths, obj) 3476 expr = add_association_filter_conditions(ref, obj, expr) 3477 association_filter_handle_inversion(op, expr, keys) 3478 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 3487 def post_load(all_records) 3488 eager_graph_build_associations(all_records) if @opts[:eager_graph] 3489 eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph]) 3490 super 3491 end