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 3319 def as_hash(key_column=nil, value_column=nil, opts=OPTS) 3320 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3321 opts = Hash[opts] 3322 opts[:all] = true 3323 end 3324 super 3325 end
If the dataset is being eagerly loaded, default to calling all instead of each.
Source
# File lib/sequel/model/associations.rb 3025 def association_join(*associations) 3026 association_inner_join(*associations) 3027 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 3036 def complex_expression_sql_append(sql, op, args) 3037 r = args[1] 3038 if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) || 3039 (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)}))))) 3040 l = args[0] 3041 if ar = model.association_reflections[l] 3042 raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false 3043 3044 if multiple 3045 klass = ar.associated_class 3046 if is_ds 3047 if r.respond_to?(:model) 3048 unless r.model <= klass 3049 # A dataset for a different model class, could be a valid regular query 3050 return super 3051 end 3052 else 3053 # Not a model dataset, could be a valid regular query 3054 return super 3055 end 3056 else 3057 unless r.all?{|x| x.is_a?(klass)} 3058 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}" 3059 end 3060 end 3061 elsif !r.is_a?(ar.associated_class) 3062 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}" 3063 end 3064 3065 if exp = association_filter_expression(op, ar, r) 3066 literal_append(sql, exp) 3067 else 3068 raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}" 3069 end 3070 elsif multiple && (is_ds || r.empty?) 3071 # Not a query designed for this support, could be a valid regular query 3072 super 3073 else 3074 raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}" 3075 end 3076 else 3077 super 3078 end 3079 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 3156 def eager(*associations) 3157 opts = @opts[:eager] 3158 association_opts = eager_options_for_associations(associations) 3159 opts = opts ? opts.merge(association_opts) : association_opts 3160 clone(:eager=>opts.freeze) 3161 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 3266 def eager_graph(*associations) 3267 eager_graph_with_options(associations) 3268 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 3290 def eager_graph_with_options(associations, opts=OPTS) 3291 return self if associations.empty? 3292 3293 opts = opts.dup unless opts.frozen? 3294 associations = [associations] unless associations.is_a?(Array) 3295 ds = if eg = @opts[:eager_graph] 3296 eg = eg.dup 3297 [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup} 3298 eg[:local] = opts 3299 ds = clone(:eager_graph=>eg) 3300 ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations) 3301 else 3302 # Each of the following have a symbol key for the table alias, with the following values: 3303 # :reciprocals :: the reciprocal value to use for this association 3304 # :reflections :: AssociationReflection instance related to this association 3305 # :requirements :: array of requirements for this association 3306 # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading 3307 opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc} 3308 ds = clone(:eager_graph=>opts) 3309 ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked 3310 end 3311 3312 ds.opts[:eager_graph].freeze 3313 ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)} 3314 ds 3315 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 3329 def to_hash_groups(key_column, value_column=nil, opts=OPTS) 3330 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3331 opts = Hash[opts] 3332 opts[:all] = true 3333 end 3334 super 3335 end
If the dataset is being eagerly loaded, default to calling all instead of each.
Source
# File lib/sequel/model/associations.rb 3341 def ungraphed 3342 ds = super.clone(:eager_graph=>nil) 3343 if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc]) 3344 ds = ds.with_row_proc(rp) 3345 end 3346 ds 3347 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 3366 def eager_graph_association(ds, model, ta, requirements, r, *associations) 3367 if r.is_a?(SQL::AliasedExpression) 3368 alias_base = r.alias 3369 if r.columns.is_a?(Hash) 3370 join_type = r.columns[:join_type] 3371 end 3372 r = r.expression 3373 else 3374 alias_base = r[:graph_alias_base] 3375 end 3376 assoc_table_alias = ds.unused_table_alias(alias_base) 3377 loader = r[:eager_grapher] 3378 if !associations.empty? 3379 if associations.first.respond_to?(:call) 3380 callback = associations.first 3381 associations = {} 3382 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) 3383 callback, assoc = pr_assoc 3384 associations = assoc.is_a?(Array) ? assoc : [assoc] 3385 end 3386 end 3387 local_opts = ds.opts[:eager_graph][:local] 3388 limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy]) 3389 3390 # SEQUEL6: remove and integrate the auto_restrict_eager_graph plugin 3391 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] 3392 if r[:conditions] && !Sequel.condition_specifier?(r[:conditions]) 3393 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]}" 3394 end 3395 3396 if r[:block] && !r[:graph_use_association_block] 3397 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]}" 3398 end 3399 end 3400 3401 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]) 3402 if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order])) 3403 ds = ds.order_append(*qualified_expression(order, assoc_table_alias)) 3404 end 3405 eager_graph = ds.opts[:eager_graph] 3406 eager_graph[:requirements][assoc_table_alias] = requirements.dup 3407 eager_graph[:reflections][assoc_table_alias] = r 3408 if limit_strategy == :ruby 3409 eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 3410 end 3411 eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2 3412 ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty? 3413 ds 3414 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 3425 def eager_graph_associations(ds, model, ta, requirements, *associations) 3426 associations.flatten.each do |association| 3427 ds = case association 3428 when Symbol, SQL::AliasedExpression 3429 ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association)) 3430 when Hash 3431 association.each do |assoc, assoc_assocs| 3432 ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs) 3433 end 3434 ds 3435 else 3436 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3437 end 3438 end 3439 ds 3440 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 3444 def eager_graph_build_associations(hashes) 3445 hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader)) 3446 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 3452 def _association_join(type, associations) 3453 clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join]) 3454 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 3458 def _eager_graph_build_associations(hashes, egl) 3459 egl.load(hashes) 3460 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 3465 def add_association_filter_conditions(ref, obj, expr) 3466 if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions? 3467 Sequel[ref.filter_by_associations_conditions_expression(obj)] 3468 else 3469 expr 3470 end 3471 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 3493 def association_filter_expression(op, ref, obj) 3494 meth = :"#{ref[:type]}_association_filter_expression" 3495 # Allow calling private association specific method to get filter expression 3496 send(meth, op, ref, obj) if respond_to?(meth, true) 3497 end
Return an expression for filtering by the given association reflection and associated object.
Source
# File lib/sequel/model/associations.rb 3501 def association_filter_handle_inversion(op, exp, cols) 3502 if op == :'!=' || op == :'NOT IN' 3503 if exp == SQL::Constants::FALSE 3504 ~exp 3505 else 3506 ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR) 3507 end 3508 else 3509 exp 3510 end 3511 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 3516 def association_filter_key_expression(keys, meths, obj) 3517 vals = if obj.is_a?(Sequel::Dataset) 3518 {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))} 3519 else 3520 vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}} 3521 return SQL::Constants::FALSE if vals.empty? 3522 if obj.is_a?(Array) 3523 if keys.length == 1 3524 meth = meths.first 3525 {keys.first=>vals.map{|o| o.get_column_value(meth)}} 3526 else 3527 {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}} 3528 end 3529 else 3530 keys.zip(meths.map{|k| obj.get_column_value(k)}) 3531 end 3532 end 3533 SQL::BooleanExpression.from_value_pairs(vals) 3534 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 3537 def check_association(model, association) 3538 raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association) 3539 raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false 3540 reflection 3541 end
Make sure the association is valid for this model, and return the related AssociationReflection
.
Source
# File lib/sequel/model/associations.rb 3545 def eager_graph_check_association(model, association) 3546 reflection = if association.is_a?(SQL::AliasedExpression) 3547 expr = association.expression 3548 if expr.is_a?(SQL::Identifier) 3549 expr = expr.value 3550 if expr.is_a?(String) 3551 expr = expr.to_sym 3552 end 3553 end 3554 3555 check_reflection = check_association(model, expr) 3556 SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns) 3557 else 3558 check_reflection = check_association(model, association) 3559 end 3560 3561 if check_reflection && check_reflection[:allow_eager_graph] == false 3562 raise Error, "eager_graph not allowed for #{reflection.inspect}" 3563 end 3564 3565 reflection 3566 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 3569 def eager_graph_loader 3570 unless egl = cache_get(:_model_eager_graph_loader) 3571 egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self)) 3572 end 3573 egl.dup 3574 end
The EagerGraphLoader
instance used for converting eager_graph
results.
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# File lib/sequel/model/associations.rb 3577 def eager_load(a, eager_assoc=@opts[:eager], m=model) 3578 return if a.empty? 3579 3580 # Reflections for all associations to eager load 3581 reflections = eager_assoc.keys.map{|assoc| m.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")} 3582 3583 perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc)) 3584 3585 reflections.each do |r| 3586 a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load] 3587 end 3588 3589 nil 3590 end
Eagerly load all specified associations.
Source
# File lib/sequel/model/associations.rb 3475 def eager_options_for_associations(associations) 3476 opts = {} 3477 associations.flatten.each do |association| 3478 case association 3479 when Symbol 3480 check_association(model, association) 3481 opts[association] = nil 3482 when Hash 3483 association.keys.each{|assoc| check_association(model, assoc)} 3484 opts.merge!(association) 3485 else 3486 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3487 end 3488 end 3489 opts 3490 end
Process the array of associations arguments (Symbols, Arrays, and Hashes), and return a hash of options suitable for cascading.
Source
# File lib/sequel/model/associations.rb 3657 def many_to_many_association_filter_expression(op, ref, obj) 3658 lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys) 3659 jt = ref.join_table_alias 3660 lpks = lpks.first if lpks.length == 1 3661 lpks = ref.qualify(model.table_name, lpks) 3662 3663 meths = if obj.is_a?(Sequel::Dataset) 3664 ref.qualify(obj.model.table_name, ref.right_primary_keys) 3665 else 3666 ref.right_primary_key_methods 3667 end 3668 3669 expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj) 3670 unless expr == SQL::Constants::FALSE 3671 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))) 3672 expr = add_association_filter_conditions(ref, obj, expr) 3673 end 3674 3675 association_filter_handle_inversion(op, expr, Array(lpks)) 3676 end
Return a subquery expression for filering by a many_to_many association
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# File lib/sequel/model/associations.rb 3680 def many_to_one_association_filter_expression(op, ref, obj) 3681 keys = ref.qualify(model.table_name, ref[:key_columns]) 3682 meths = if obj.is_a?(Sequel::Dataset) 3683 ref.qualify(obj.model.table_name, ref.primary_keys) 3684 else 3685 ref.primary_key_methods 3686 end 3687 3688 expr = association_filter_key_expression(keys, meths, obj) 3689 expr = add_association_filter_conditions(ref, obj, expr) 3690 association_filter_handle_inversion(op, expr, keys) 3691 end
Return a simple equality expression for filering by a many_to_one association
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# File lib/sequel/model/associations.rb 3708 def non_sql_option?(key) 3709 super || key == :eager || key == :eager_graph 3710 end
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# File lib/sequel/model/associations.rb 3694 def one_to_many_association_filter_expression(op, ref, obj) 3695 keys = ref.qualify(model.table_name, ref[:primary_key_columns]) 3696 meths = if obj.is_a?(Sequel::Dataset) 3697 ref.qualify(obj.model.table_name, ref[:keys]) 3698 else 3699 ref[:key_methods] 3700 end 3701 3702 expr = association_filter_key_expression(keys, meths, obj) 3703 expr = add_association_filter_conditions(ref, obj, expr) 3704 association_filter_handle_inversion(op, expr, keys) 3705 end
Return a simple equality expression for filering by a one_to_* association
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# File lib/sequel/model/associations.rb 3652 def perform_eager_load(loader, eo) 3653 loader.call(eo) 3654 end
Perform eager loading for a single association using the loader and eager options.
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# File lib/sequel/model/associations.rb 3645 def perform_eager_loads(eager_load_data) 3646 eager_load_data.map do |loader, eo| 3647 perform_eager_load(loader, eo) 3648 end 3649 end
Using the hash of loaders and eager options, perform the eager loading.
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# File lib/sequel/model/associations.rb 3714 def post_load(all_records) 3715 eager_graph_build_associations(all_records) if @opts[:eager_graph] 3716 eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph]) 3717 super 3718 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 3593 def prepare_eager_load(a, reflections, eager_assoc) 3594 eager_load_data = {} 3595 3596 # Key is foreign/primary key name symbol. 3597 # Value is hash with keys being foreign/primary key values (generally integers) 3598 # and values being an array of current model objects with that specific foreign/primary key 3599 key_hash = {} 3600 3601 # Populate the key_hash entry for each association being eagerly loaded 3602 reflections.each do |r| 3603 if key = r.eager_loader_key 3604 # key_hash for this key has already been populated, 3605 # skip populating again so that duplicate values 3606 # aren't added. 3607 unless id_map = key_hash[key] 3608 id_map = key_hash[key] = Hash.new{|h,k| h[k] = []} 3609 3610 # Supporting both single (Symbol) and composite (Array) keys. 3611 a.each do |rec| 3612 case key 3613 when Array 3614 if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all? 3615 id_map[k] << rec 3616 end 3617 when Symbol 3618 if k = rec.get_column_value(key) 3619 id_map[k] << rec 3620 end 3621 else 3622 raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}" 3623 end 3624 end 3625 end 3626 else 3627 id_map = nil 3628 end 3629 3630 associations = eager_assoc[r[:name]] 3631 if associations.respond_to?(:call) 3632 eager_block = associations 3633 associations = OPTS 3634 elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call) 3635 eager_block, associations = pr_assoc 3636 end 3637 3638 eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map} 3639 end 3640 3641 eager_load_data 3642 end
Prepare a hash loaders and eager options which will be used to implement the eager loading.