Module: OccamsRecord::EagerLoaders::Builder

Included in:
AdHocBase, Base, PolymorphicBelongsTo, Query, RawQuery
Defined in:
lib/occams-record/eager_loaders/builder.rb

Overview

Methods for adding eager loading to a query.

Users MUST have an OccamsRecord::EagerLoaders::Context at @eager_loaders.

Instance Method Summary collapse

Instance Method Details

#eager_load(assoc, scope = nil, select: nil, use: nil, as: nil, from: nil, optimizer: :select) { ... } ⇒ Object

Specify an association to be eager-loaded. For maximum memory savings, only SELECT the colums you actually need.

ActiveRecord::Relation on which you may call all the normal query hethods (select, where, etc) as well as any scopes you’ve defined on the model.

Yields:

  • a block where you may perform eager loading on this association (optional)



24
25
26
27
 
# File 'lib/occams-record/eager_loaders/builder.rb', line 24

def eager_load(assoc, scope = nil, select: nil, use: nil, as: nil, from: nil, optimizer: :select, &builder)
  @eager_loaders.add(assoc, scope, select: select, use: use, as: as, from: from, optimizer: optimizer, &builder)
  self
end

#eager_load_many(name, mapping, sql, binds: {}, model: nil, use: nil) { ... } ⇒ Object

Specify some arbitrary SQL to be loaded into some arbitrary attribute (“name”). The attribute will hold an array of 0 or more associated records.

In the example below, :parts is NOT an association on Widget. Though if it where it would be a has_many. The mapping argument says “The id column in the parent (Widget) maps to the widget_id column in the children.

The %ids bind param will be provided for you, and in this case will be all the id values from the Widget query.

res = OccamsRecord.
  query(Widget.order("name")).
  eager_load_many(:parts, {:id => :widget_id}, "
    SELECT * FROM parts WHERE widget_id IN (%{ids}) AND sku NOT IN (%{bad_skus})
  ", binds: {
    bad_skus: ["G90023ASDf0"]
  }).
  run

Yields:

  • eager load associations nested under this one



110
111
112
113
 
# File 'lib/occams-record/eager_loaders/builder.rb', line 110

def eager_load_many(name, mapping, sql, binds: {}, model: nil, use: nil, &builder)
  @eager_loaders << EagerLoaders::AdHocMany.new(name, mapping, sql, binds: binds, model: model, use: use, &builder)
  self
end

#eager_load_one(name, mapping, sql, binds: {}, model: nil, use: nil) { ... } ⇒ Object

Specify some arbitrary SQL to be loaded into some arbitrary attribute (“name”). The attribute will hold either one record or none.

In the example below, :category is NOT an association on Widget. Though if it where it would be a belongs_to. The mapping argument says “The category_id in the parent (Widget) maps to the id column in the child records (Category).

The %category_ids bind param will be provided for you, and in this case will be all the category_id values from the Widget query.

res = OccamsRecord.
  query(Widget.order("name")).
  eager_load_one(:category, {:category_id => :id}, "
    SELECT * FROM categories WHERE id IN (%{category_ids}) AND name != %{bad_name}
  ", binds: {
    bad_name: "Bad Category"
  }).
  run

Yields:

  • eager load associations nested under this one



77
78
79
80
 
# File 'lib/occams-record/eager_loaders/builder.rb', line 77

def eager_load_one(name, mapping, sql, binds: {}, model: nil, use: nil, &builder)
  @eager_loaders << EagerLoaders::AdHocOne.new(name, mapping, sql, binds: binds, model: model, use: use, &builder)
  self
end

#nest(assoc, scope = nil, select: nil, use: nil, as: nil, from: nil, optimizer: :select) ⇒ OccamsRecord::EagerLoaders::Base

Same as eager_load, except it returns the new eager loader object instead of self. You can use the new object to call “nest” again, programtically building up nested eager loads instead of passing nested blocks.

ActiveRecord::Relation on which you may call all the normal query hethods (select, where, etc) as well as any scopes you’ve defined on the model.

Raises:

  • (ArgumentError) 


44
45
46
47
48
 
# File 'lib/occams-record/eager_loaders/builder.rb', line 44

def nest(assoc, scope = nil, select: nil, use: nil, as: nil, from: nil, optimizer: :select)
  raise ArgumentError, "OccamsRecord::EagerLoaders::Builder#nest does not accept a block!" if block_given?
  @eager_loaders.add(assoc, scope, select: select, use: use, as: as, from: from, optimizer: optimizer) ||
    raise("OccamsRecord::EagerLoaders::Builder#nest may not be called under a polymorphic association")
end