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 3344 def as_hash(key_column=nil, value_column=nil, opts=OPTS) 3345 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3346 opts = Hash[opts] 3347 opts[:all] = true 3348 end 3349 super 3350 end
If the dataset is being eagerly loaded, default to calling all instead of each.
Source
# File lib/sequel/model/associations.rb 3050 def association_join(*associations) 3051 association_inner_join(*associations) 3052 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 3061 def complex_expression_sql_append(sql, op, args) 3062 r = args[1] 3063 if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) || 3064 (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)}))))) 3065 l = args[0] 3066 if ar = model.association_reflections[l] 3067 raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false 3068 3069 if multiple 3070 klass = ar.associated_class 3071 if is_ds 3072 if r.respond_to?(:model) 3073 unless r.model <= klass 3074 # A dataset for a different model class, could be a valid regular query 3075 return super 3076 end 3077 else 3078 # Not a model dataset, could be a valid regular query 3079 return super 3080 end 3081 else 3082 unless r.all?{|x| x.is_a?(klass)} 3083 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}" 3084 end 3085 end 3086 elsif !r.is_a?(ar.associated_class) 3087 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}" 3088 end 3089 3090 if exp = association_filter_expression(op, ar, r) 3091 literal_append(sql, exp) 3092 else 3093 raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}" 3094 end 3095 elsif multiple && (is_ds || r.empty?) 3096 # Not a query designed for this support, could be a valid regular query 3097 super 3098 else 3099 raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}" 3100 end 3101 else 3102 super 3103 end 3104 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 3181 def eager(*associations) 3182 opts = @opts[:eager] 3183 association_opts = eager_options_for_associations(associations) 3184 opts = opts ? opts.merge(association_opts) : association_opts 3185 clone(:eager=>opts.freeze) 3186 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 3291 def eager_graph(*associations) 3292 eager_graph_with_options(associations) 3293 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 3315 def eager_graph_with_options(associations, opts=OPTS) 3316 return self if associations.empty? 3317 3318 opts = opts.dup unless opts.frozen? 3319 associations = [associations] unless associations.is_a?(Array) 3320 ds = if eg = @opts[:eager_graph] 3321 eg = eg.dup 3322 [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup} 3323 eg[:local] = opts 3324 ds = clone(:eager_graph=>eg) 3325 ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations) 3326 else 3327 # Each of the following have a symbol key for the table alias, with the following values: 3328 # :reciprocals :: the reciprocal value to use for this association 3329 # :reflections :: AssociationReflection instance related to this association 3330 # :requirements :: array of requirements for this association 3331 # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading 3332 opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc} 3333 ds = clone(:eager_graph=>opts) 3334 ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked 3335 end 3336 3337 ds.opts[:eager_graph].freeze 3338 ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)} 3339 ds 3340 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 3354 def to_hash_groups(key_column, value_column=nil, opts=OPTS) 3355 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3356 opts = Hash[opts] 3357 opts[:all] = true 3358 end 3359 super 3360 end
If the dataset is being eagerly loaded, default to calling all instead of each.
Source
# File lib/sequel/model/associations.rb 3366 def ungraphed 3367 ds = super.clone(:eager_graph=>nil) 3368 if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc]) 3369 ds = ds.with_row_proc(rp) 3370 end 3371 ds 3372 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 3391 def eager_graph_association(ds, model, ta, requirements, r, *associations) 3392 if r.is_a?(SQL::AliasedExpression) 3393 alias_base = r.alias 3394 if r.columns.is_a?(Hash) 3395 join_type = r.columns[:join_type] 3396 end 3397 r = r.expression 3398 else 3399 alias_base = r[:graph_alias_base] 3400 end 3401 assoc_table_alias = ds.unused_table_alias(alias_base) 3402 loader = r[:eager_grapher] 3403 if !associations.empty? 3404 if associations.first.respond_to?(:call) 3405 callback = associations.first 3406 associations = {} 3407 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) 3408 callback, assoc = pr_assoc 3409 associations = assoc.is_a?(Array) ? assoc : [assoc] 3410 end 3411 end 3412 local_opts = ds.opts[:eager_graph][:local] 3413 limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy]) 3414 3415 # SEQUEL6: remove and integrate the auto_restrict_eager_graph plugin 3416 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] 3417 if r[:conditions] && !Sequel.condition_specifier?(r[:conditions]) 3418 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]}" 3419 end 3420 3421 if r[:block] && !r[:graph_use_association_block] 3422 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]}" 3423 end 3424 end 3425 3426 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]) 3427 if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order])) 3428 ds = ds.order_append(*qualified_expression(order, assoc_table_alias)) 3429 end 3430 eager_graph = ds.opts[:eager_graph] 3431 eager_graph[:requirements][assoc_table_alias] = requirements.dup 3432 eager_graph[:reflections][assoc_table_alias] = r 3433 if limit_strategy == :ruby 3434 eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 3435 end 3436 eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2 3437 ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty? 3438 ds 3439 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::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
Source
# File lib/sequel/model/associations.rb 3450 def eager_graph_associations(ds, model, ta, requirements, *associations) 3451 associations.flatten.each do |association| 3452 ds = case association 3453 when Symbol, SQL::AliasedExpression 3454 ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association)) 3455 when Hash 3456 association.each do |assoc, assoc_assocs| 3457 ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs) 3458 end 3459 ds 3460 else 3461 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3462 end 3463 end 3464 ds 3465 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 3469 def eager_graph_build_associations(hashes) 3470 hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader)) 3471 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 3477 def _association_join(type, associations) 3478 clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join]) 3479 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 3483 def _eager_graph_build_associations(hashes, egl) 3484 egl.load(hashes) 3485 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 3490 def add_association_filter_conditions(ref, obj, expr) 3491 if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions? 3492 Sequel[ref.filter_by_associations_conditions_expression(obj)] 3493 else 3494 expr 3495 end 3496 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 3518 def association_filter_expression(op, ref, obj) 3519 meth = :"#{ref[:type]}_association_filter_expression" 3520 # Allow calling private association specific method to get filter expression 3521 send(meth, op, ref, obj) if respond_to?(meth, true) 3522 end
Return an expression for filtering by the given association reflection and associated object.
Source
# File lib/sequel/model/associations.rb 3526 def association_filter_handle_inversion(op, exp, cols) 3527 if op == :'!=' || op == :'NOT IN' 3528 if exp == SQL::Constants::FALSE 3529 ~exp 3530 else 3531 ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR) 3532 end 3533 else 3534 exp 3535 end 3536 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 3541 def association_filter_key_expression(keys, meths, obj) 3542 vals = if obj.is_a?(Sequel::Dataset) 3543 {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))} 3544 else 3545 vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}} 3546 return SQL::Constants::FALSE if vals.empty? 3547 if obj.is_a?(Array) 3548 if keys.length == 1 3549 meth = meths.first 3550 {keys.first=>vals.map{|o| o.get_column_value(meth)}} 3551 else 3552 {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}} 3553 end 3554 else 3555 keys.zip(meths.map{|k| obj.get_column_value(k)}) 3556 end 3557 end 3558 SQL::BooleanExpression.from_value_pairs(vals) 3559 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 3562 def check_association(model, association) 3563 raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association) 3564 raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false 3565 reflection 3566 end
Make sure the association is valid for this model, and return the related AssociationReflection
.
Source
# File lib/sequel/model/associations.rb 3570 def eager_graph_check_association(model, association) 3571 reflection = if association.is_a?(SQL::AliasedExpression) 3572 expr = association.expression 3573 if expr.is_a?(SQL::Identifier) 3574 expr = expr.value 3575 if expr.is_a?(String) 3576 expr = expr.to_sym 3577 end 3578 end 3579 3580 check_reflection = check_association(model, expr) 3581 SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns) 3582 else 3583 check_reflection = check_association(model, association) 3584 end 3585 3586 if check_reflection && check_reflection[:allow_eager_graph] == false 3587 raise Error, "eager_graph not allowed for #{reflection.inspect}" 3588 end 3589 3590 reflection 3591 end
Allow associations that are eagerly graphed to be specified as an SQL::AliasedExpression
, for per-call determining of the alias base.
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# File lib/sequel/model/associations.rb 3594 def eager_graph_loader 3595 unless egl = cache_get(:_model_eager_graph_loader) 3596 egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self)) 3597 end 3598 egl.dup 3599 end
The EagerGraphLoader
instance used for converting eager_graph
results.
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# File lib/sequel/model/associations.rb 3602 def eager_load(a, eager_assoc=@opts[:eager], m=model) 3603 return if a.empty? 3604 3605 # Reflections for all associations to eager load 3606 reflections = eager_assoc.keys.map{|assoc| m.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")} 3607 3608 perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc)) 3609 3610 reflections.each do |r| 3611 a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load] 3612 end 3613 3614 nil 3615 end
Eagerly load all specified associations.
Source
# File lib/sequel/model/associations.rb 3500 def eager_options_for_associations(associations) 3501 opts = {} 3502 associations.flatten.each do |association| 3503 case association 3504 when Symbol 3505 check_association(model, association) 3506 opts[association] = nil 3507 when Hash 3508 association.keys.each{|assoc| check_association(model, assoc)} 3509 opts.merge!(association) 3510 else 3511 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3512 end 3513 end 3514 opts 3515 end
Process the array of associations arguments (Symbols, Arrays, and Hashes), and return a hash of options suitable for cascading.
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# File lib/sequel/model/associations.rb 3682 def many_to_many_association_filter_expression(op, ref, obj) 3683 lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys) 3684 jt = ref.join_table_alias 3685 lpks = lpks.first if lpks.length == 1 3686 lpks = ref.qualify(model.table_name, lpks) 3687 3688 meths = if obj.is_a?(Sequel::Dataset) 3689 ref.qualify(obj.model.table_name, ref.right_primary_keys) 3690 else 3691 ref.right_primary_key_methods 3692 end 3693 3694 expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj) 3695 unless expr == SQL::Constants::FALSE 3696 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))) 3697 expr = add_association_filter_conditions(ref, obj, expr) 3698 end 3699 3700 association_filter_handle_inversion(op, expr, Array(lpks)) 3701 end
Return a subquery expression for filering by a many_to_many association
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# File lib/sequel/model/associations.rb 3705 def many_to_one_association_filter_expression(op, ref, obj) 3706 keys = ref.qualify(model.table_name, ref[:key_columns]) 3707 meths = if obj.is_a?(Sequel::Dataset) 3708 ref.qualify(obj.model.table_name, ref.primary_keys) 3709 else 3710 ref.primary_key_methods 3711 end 3712 3713 expr = association_filter_key_expression(keys, meths, obj) 3714 expr = add_association_filter_conditions(ref, obj, expr) 3715 association_filter_handle_inversion(op, expr, keys) 3716 end
Return a simple equality expression for filering by a many_to_one association
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# File lib/sequel/model/associations.rb 3733 def non_sql_option?(key) 3734 super || key == :eager || key == :eager_graph 3735 end
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# File lib/sequel/model/associations.rb 3719 def one_to_many_association_filter_expression(op, ref, obj) 3720 keys = ref.qualify(model.table_name, ref[:primary_key_columns]) 3721 meths = if obj.is_a?(Sequel::Dataset) 3722 ref.qualify(obj.model.table_name, ref[:keys]) 3723 else 3724 ref[:key_methods] 3725 end 3726 3727 expr = association_filter_key_expression(keys, meths, obj) 3728 expr = add_association_filter_conditions(ref, obj, expr) 3729 association_filter_handle_inversion(op, expr, keys) 3730 end
Return a simple equality expression for filering by a one_to_* association
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# File lib/sequel/model/associations.rb 3677 def perform_eager_load(loader, eo) 3678 loader.call(eo) 3679 end
Perform eager loading for a single association using the loader and eager options.
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# File lib/sequel/model/associations.rb 3670 def perform_eager_loads(eager_load_data) 3671 eager_load_data.map do |loader, eo| 3672 perform_eager_load(loader, eo) 3673 end 3674 end
Using the hash of loaders and eager options, perform the eager loading.
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# File lib/sequel/model/associations.rb 3739 def post_load(all_records) 3740 eager_graph_build_associations(all_records) if @opts[:eager_graph] 3741 eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph]) 3742 super 3743 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 3618 def prepare_eager_load(a, reflections, eager_assoc) 3619 eager_load_data = {}.compare_by_identity 3620 3621 # Key is foreign/primary key name symbol. 3622 # Value is hash with keys being foreign/primary key values (generally integers) 3623 # and values being an array of current model objects with that specific foreign/primary key 3624 key_hash = {} 3625 3626 # Populate the key_hash entry for each association being eagerly loaded 3627 reflections.each do |r| 3628 if key = r.eager_loader_key 3629 # key_hash for this key has already been populated, 3630 # skip populating again so that duplicate values 3631 # aren't added. 3632 unless id_map = key_hash[key] 3633 id_map = key_hash[key] = Hash.new{|h,k| h[k] = []} 3634 3635 # Supporting both single (Symbol) and composite (Array) keys. 3636 a.each do |rec| 3637 case key 3638 when Array 3639 if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all? 3640 id_map[k] << rec 3641 end 3642 when Symbol 3643 if k = rec.get_column_value(key) 3644 id_map[k] << rec 3645 end 3646 else 3647 raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}" 3648 end 3649 end 3650 end 3651 else 3652 id_map = nil 3653 end 3654 3655 associations = eager_assoc[r[:name]] 3656 if associations.respond_to?(:call) 3657 eager_block = associations 3658 associations = OPTS 3659 elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call) 3660 eager_block, associations = pr_assoc 3661 end 3662 3663 eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map} 3664 end 3665 3666 eager_load_data 3667 end
Prepare a hash loaders and eager options which will be used to implement the eager loading.