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 3304 def as_hash(key_column=nil, value_column=nil, opts=OPTS) 3305 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3306 opts = Hash[opts] 3307 opts[:all] = true 3308 end 3309 super 3310 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 3010 def association_join(*associations) 3011 association_inner_join(*associations) 3012 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 3021 def complex_expression_sql_append(sql, op, args) 3022 r = args[1] 3023 if (((op == :'=' || op == :'!=') && r.is_a?(Sequel::Model)) || 3024 (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)}))))) 3025 l = args[0] 3026 if ar = model.association_reflections[l] 3027 raise Error, "filtering by associations is not allowed for #{ar.inspect}" if ar[:allow_filtering_by] == false 3028 3029 if multiple 3030 klass = ar.associated_class 3031 if is_ds 3032 if r.respond_to?(:model) 3033 unless r.model <= klass 3034 # A dataset for a different model class, could be a valid regular query 3035 return super 3036 end 3037 else 3038 # Not a model dataset, could be a valid regular query 3039 return super 3040 end 3041 else 3042 unless r.all?{|x| x.is_a?(klass)} 3043 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}" 3044 end 3045 end 3046 elsif !r.is_a?(ar.associated_class) 3047 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}" 3048 end 3049 3050 if exp = association_filter_expression(op, ar, r) 3051 literal_append(sql, exp) 3052 else 3053 raise Sequel::Error, "invalid association type #{ar[:type].inspect} for association #{l.inspect} used in dataset filter for model #{model.inspect}" 3054 end 3055 elsif multiple && (is_ds || r.empty?) 3056 # Not a query designed for this support, could be a valid regular query 3057 super 3058 else 3059 raise Sequel::Error, "invalid association #{l.inspect} used in dataset filter for model #{model.inspect}" 3060 end 3061 else 3062 super 3063 end 3064 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 3141 def eager(*associations) 3142 opts = @opts[:eager] 3143 association_opts = eager_options_for_associations(associations) 3144 opts = opts ? opts.merge(association_opts) : association_opts 3145 clone(:eager=>opts.freeze) 3146 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)
# File lib/sequel/model/associations.rb 3251 def eager_graph(*associations) 3252 eager_graph_with_options(associations) 3253 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 3275 def eager_graph_with_options(associations, opts=OPTS) 3276 return self if associations.empty? 3277 3278 opts = opts.dup unless opts.frozen? 3279 associations = [associations] unless associations.is_a?(Array) 3280 ds = if eg = @opts[:eager_graph] 3281 eg = eg.dup 3282 [:requirements, :reflections, :reciprocals, :limits].each{|k| eg[k] = eg[k].dup} 3283 eg[:local] = opts 3284 ds = clone(:eager_graph=>eg) 3285 ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations) 3286 else 3287 # Each of the following have a symbol key for the table alias, with the following values: 3288 # :reciprocals :: the reciprocal value to use for this association 3289 # :reflections :: AssociationReflection instance related to this association 3290 # :requirements :: array of requirements for this association 3291 # :limits :: Any limit/offset array slicing that need to be handled in ruby land after loading 3292 opts = {:requirements=>{}, :master=>alias_symbol(first_source), :reflections=>{}, :reciprocals=>{}, :limits=>{}, :local=>opts, :cartesian_product_number=>0, :row_proc=>row_proc} 3293 ds = clone(:eager_graph=>opts) 3294 ds = ds.eager_graph_associations(ds, model, ds.opts[:eager_graph][:master], [], *associations).naked 3295 end 3296 3297 ds.opts[:eager_graph].freeze 3298 ds.opts[:eager_graph].each_value{|v| v.freeze if v.is_a?(Hash)} 3299 ds 3300 end
If the dataset is being eagerly loaded, default to calling all instead of each.
# File lib/sequel/model/associations.rb 3314 def to_hash_groups(key_column, value_column=nil, opts=OPTS) 3315 if (@opts[:eager_graph] || @opts[:eager]) && !opts.has_key?(:all) 3316 opts = Hash[opts] 3317 opts[:all] = true 3318 end 3319 super 3320 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 3326 def ungraphed 3327 ds = super.clone(:eager_graph=>nil) 3328 if (eg = @opts[:eager_graph]) && (rp = eg[:row_proc]) 3329 ds = ds.with_row_proc(rp) 3330 end 3331 ds 3332 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 3351 def eager_graph_association(ds, model, ta, requirements, r, *associations) 3352 if r.is_a?(SQL::AliasedExpression) 3353 alias_base = r.alias 3354 if r.columns.is_a?(Hash) 3355 join_type = r.columns[:join_type] 3356 end 3357 r = r.expression 3358 else 3359 alias_base = r[:graph_alias_base] 3360 end 3361 assoc_table_alias = ds.unused_table_alias(alias_base) 3362 loader = r[:eager_grapher] 3363 if !associations.empty? 3364 if associations.first.respond_to?(:call) 3365 callback = associations.first 3366 associations = {} 3367 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) 3368 callback, assoc = pr_assoc 3369 associations = assoc.is_a?(Array) ? assoc : [assoc] 3370 end 3371 end 3372 local_opts = ds.opts[:eager_graph][:local] 3373 limit_strategy = r.eager_graph_limit_strategy(local_opts[:limit_strategy]) 3374 3375 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) 3376 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]}" 3377 end 3378 3379 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]) 3380 if r[:order_eager_graph] && (order = r.fetch(:graph_order, r[:order])) 3381 ds = ds.order_append(*qualified_expression(order, assoc_table_alias)) 3382 end 3383 eager_graph = ds.opts[:eager_graph] 3384 eager_graph[:requirements][assoc_table_alias] = requirements.dup 3385 eager_graph[:reflections][assoc_table_alias] = r 3386 if limit_strategy == :ruby 3387 eager_graph[:limits][assoc_table_alias] = r.limit_and_offset 3388 end 3389 eager_graph[:cartesian_product_number] += r[:cartesian_product_number] || 2 3390 ds = ds.eager_graph_associations(ds, r.associated_class, assoc_table_alias, requirements + [assoc_table_alias], *associations) unless associations.empty? 3391 ds 3392 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 3403 def eager_graph_associations(ds, model, ta, requirements, *associations) 3404 associations.flatten.each do |association| 3405 ds = case association 3406 when Symbol, SQL::AliasedExpression 3407 ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, association)) 3408 when Hash 3409 association.each do |assoc, assoc_assocs| 3410 ds = ds.eager_graph_association(ds, model, ta, requirements, eager_graph_check_association(model, assoc), assoc_assocs) 3411 end 3412 ds 3413 else 3414 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3415 end 3416 end 3417 ds 3418 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 3422 def eager_graph_build_associations(hashes) 3423 hashes.replace(_eager_graph_build_associations(hashes, eager_graph_loader)) 3424 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 3430 def _association_join(type, associations) 3431 clone(:join=>clone(:graph_from_self=>false).eager_graph_with_options(associations, :join_type=>type, :join_only=>true).opts[:join]) 3432 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 3436 def _eager_graph_build_associations(hashes, egl) 3437 egl.load(hashes) 3438 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 3443 def add_association_filter_conditions(ref, obj, expr) 3444 if expr != SQL::Constants::FALSE && ref.filter_by_associations_add_conditions? 3445 Sequel[ref.filter_by_associations_conditions_expression(obj)] 3446 else 3447 expr 3448 end 3449 end
Return an expression for filtering by the given association reflection and associated object.
# File lib/sequel/model/associations.rb 3471 def association_filter_expression(op, ref, obj) 3472 meth = :"#{ref[:type]}_association_filter_expression" 3473 # Allow calling private association specific method to get filter expression 3474 send(meth, op, ref, obj) if respond_to?(meth, true) 3475 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 3479 def association_filter_handle_inversion(op, exp, cols) 3480 if op == :'!=' || op == :'NOT IN' 3481 if exp == SQL::Constants::FALSE 3482 ~exp 3483 else 3484 ~exp | Sequel::SQL::BooleanExpression.from_value_pairs(cols.zip([]), :OR) 3485 end 3486 else 3487 exp 3488 end 3489 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 3494 def association_filter_key_expression(keys, meths, obj) 3495 vals = if obj.is_a?(Sequel::Dataset) 3496 {(keys.length == 1 ? keys.first : keys)=>obj.select(*meths).exclude(Sequel::SQL::BooleanExpression.from_value_pairs(meths.zip([]), :OR))} 3497 else 3498 vals = Array(obj).reject{|o| !meths.all?{|m| o.get_column_value(m)}} 3499 return SQL::Constants::FALSE if vals.empty? 3500 if obj.is_a?(Array) 3501 if keys.length == 1 3502 meth = meths.first 3503 {keys.first=>vals.map{|o| o.get_column_value(meth)}} 3504 else 3505 {keys=>vals.map{|o| meths.map{|m| o.get_column_value(m)}}} 3506 end 3507 else 3508 keys.zip(meths.map{|k| obj.get_column_value(k)}) 3509 end 3510 end 3511 SQL::BooleanExpression.from_value_pairs(vals) 3512 end
Make sure the association is valid for this model, and return the related AssociationReflection
.
# File lib/sequel/model/associations.rb 3515 def check_association(model, association) 3516 raise(Sequel::UndefinedAssociation, "Invalid association #{association} for #{model.name}") unless reflection = model.association_reflection(association) 3517 raise(Sequel::Error, "Eager loading is not allowed for #{model.name} association #{association}") if reflection[:allow_eager] == false 3518 reflection 3519 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 3523 def eager_graph_check_association(model, association) 3524 reflection = if association.is_a?(SQL::AliasedExpression) 3525 expr = association.expression 3526 if expr.is_a?(SQL::Identifier) 3527 expr = expr.value 3528 if expr.is_a?(String) 3529 expr = expr.to_sym 3530 end 3531 end 3532 3533 check_reflection = check_association(model, expr) 3534 SQL::AliasedExpression.new(check_reflection, association.alias || expr, association.columns) 3535 else 3536 check_reflection = check_association(model, association) 3537 end 3538 3539 if check_reflection && check_reflection[:allow_eager_graph] == false 3540 raise Error, "eager_graph not allowed for #{reflection.inspect}" 3541 end 3542 3543 reflection 3544 end
The EagerGraphLoader
instance used for converting eager_graph
results.
# File lib/sequel/model/associations.rb 3547 def eager_graph_loader 3548 unless egl = cache_get(:_model_eager_graph_loader) 3549 egl = cache_set(:_model_eager_graph_loader, EagerGraphLoader.new(self)) 3550 end 3551 egl.dup 3552 end
Eagerly load all specified associations.
# File lib/sequel/model/associations.rb 3555 def eager_load(a, eager_assoc=@opts[:eager]) 3556 return if a.empty? 3557 3558 # Reflections for all associations to eager load 3559 reflections = eager_assoc.keys.map{|assoc| model.association_reflection(assoc) || (raise Sequel::UndefinedAssociation, "Model: #{self}, Association: #{assoc}")} 3560 3561 perform_eager_loads(prepare_eager_load(a, reflections, eager_assoc)) 3562 3563 reflections.each do |r| 3564 a.each{|object| object.send(:run_association_callbacks, r, :after_load, object.associations[r[:name]])} if r[:after_load] 3565 end 3566 3567 nil 3568 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 3453 def eager_options_for_associations(associations) 3454 opts = {} 3455 associations.flatten.each do |association| 3456 case association 3457 when Symbol 3458 check_association(model, association) 3459 opts[association] = nil 3460 when Hash 3461 association.keys.each{|assoc| check_association(model, assoc)} 3462 opts.merge!(association) 3463 else 3464 raise(Sequel::Error, 'Associations must be in the form of a symbol or hash') 3465 end 3466 end 3467 opts 3468 end
Return a subquery expression for filering by a many_to_many association
# File lib/sequel/model/associations.rb 3635 def many_to_many_association_filter_expression(op, ref, obj) 3636 lpks, lks, rks = ref.values_at(:left_primary_key_columns, :left_keys, :right_keys) 3637 jt = ref.join_table_alias 3638 lpks = lpks.first if lpks.length == 1 3639 lpks = ref.qualify(model.table_name, lpks) 3640 3641 meths = if obj.is_a?(Sequel::Dataset) 3642 ref.qualify(obj.model.table_name, ref.right_primary_keys) 3643 else 3644 ref.right_primary_key_methods 3645 end 3646 3647 expr = association_filter_key_expression(ref.qualify(jt, rks), meths, obj) 3648 unless expr == SQL::Constants::FALSE 3649 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))) 3650 expr = add_association_filter_conditions(ref, obj, expr) 3651 end 3652 3653 association_filter_handle_inversion(op, expr, Array(lpks)) 3654 end
Return a simple equality expression for filering by a many_to_one association
# File lib/sequel/model/associations.rb 3658 def many_to_one_association_filter_expression(op, ref, obj) 3659 keys = ref.qualify(model.table_name, ref[:key_columns]) 3660 meths = if obj.is_a?(Sequel::Dataset) 3661 ref.qualify(obj.model.table_name, ref.primary_keys) 3662 else 3663 ref.primary_key_methods 3664 end 3665 3666 expr = association_filter_key_expression(keys, meths, obj) 3667 expr = add_association_filter_conditions(ref, obj, expr) 3668 association_filter_handle_inversion(op, expr, keys) 3669 end
# File lib/sequel/model/associations.rb 3686 def non_sql_option?(key) 3687 super || key == :eager || key == :eager_graph 3688 end
Return a simple equality expression for filering by a one_to_* association
# File lib/sequel/model/associations.rb 3672 def one_to_many_association_filter_expression(op, ref, obj) 3673 keys = ref.qualify(model.table_name, ref[:primary_key_columns]) 3674 meths = if obj.is_a?(Sequel::Dataset) 3675 ref.qualify(obj.model.table_name, ref[:keys]) 3676 else 3677 ref[:key_methods] 3678 end 3679 3680 expr = association_filter_key_expression(keys, meths, obj) 3681 expr = add_association_filter_conditions(ref, obj, expr) 3682 association_filter_handle_inversion(op, expr, keys) 3683 end
Perform eager loading for a single association using the loader and eager options.
# File lib/sequel/model/associations.rb 3630 def perform_eager_load(loader, eo) 3631 loader.call(eo) 3632 end
Using the hash of loaders and eager options, perform the eager loading.
# File lib/sequel/model/associations.rb 3623 def perform_eager_loads(eager_load_data) 3624 eager_load_data.map do |loader, eo| 3625 perform_eager_load(loader, eo) 3626 end 3627 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 3692 def post_load(all_records) 3693 eager_graph_build_associations(all_records) if @opts[:eager_graph] 3694 eager_load(all_records) if @opts[:eager] && (row_proc || @opts[:eager_graph]) 3695 super 3696 end
Prepare a hash loaders and eager options which will be used to implement the eager loading.
# File lib/sequel/model/associations.rb 3571 def prepare_eager_load(a, reflections, eager_assoc) 3572 eager_load_data = {} 3573 3574 # Key is foreign/primary key name symbol. 3575 # Value is hash with keys being foreign/primary key values (generally integers) 3576 # and values being an array of current model objects with that specific foreign/primary key 3577 key_hash = {} 3578 3579 # Populate the key_hash entry for each association being eagerly loaded 3580 reflections.each do |r| 3581 if key = r.eager_loader_key 3582 # key_hash for this key has already been populated, 3583 # skip populating again so that duplicate values 3584 # aren't added. 3585 unless id_map = key_hash[key] 3586 id_map = key_hash[key] = Hash.new{|h,k| h[k] = []} 3587 3588 # Supporting both single (Symbol) and composite (Array) keys. 3589 a.each do |rec| 3590 case key 3591 when Array 3592 if (k = key.map{|k2| rec.get_column_value(k2)}) && k.all? 3593 id_map[k] << rec 3594 end 3595 when Symbol 3596 if k = rec.get_column_value(key) 3597 id_map[k] << rec 3598 end 3599 else 3600 raise Error, "unhandled eager_loader_key #{key.inspect} for association #{r[:name]}" 3601 end 3602 end 3603 end 3604 else 3605 id_map = nil 3606 end 3607 3608 associations = eager_assoc[r[:name]] 3609 if associations.respond_to?(:call) 3610 eager_block = associations 3611 associations = OPTS 3612 elsif associations.is_a?(Hash) && associations.length == 1 && (pr_assoc = associations.to_a.first) && pr_assoc.first.respond_to?(:call) 3613 eager_block, associations = pr_assoc 3614 end 3615 3616 eager_load_data[r[:eager_loader]] = {:key_hash=>key_hash, :rows=>a, :associations=>associations, :self=>self, :eager_block=>eager_block, :id_map=>id_map} 3617 end 3618 3619 eager_load_data 3620 end