Module: Sequel::Plugins::Finder::ClassMethods

Defined in:
lib/sequel/plugins/finder.rb

Instance Method Summary collapse

Instance Method Details

#finder(meth = OPTS, opts = OPTS, &block) ⇒ Object

Create an optimized finder method using a dataset placeholder literalizer. This pre-computes the SQL to use for the query, except for given arguments.

There are two ways to use this. The recommended way is to pass a symbol that represents a model class method that returns a dataset:

def Artist.by_name(name)
  where(name: name)
end

Artist.finder :by_name

This creates an optimized first_by_name method, which you can call normally:

Artist.first_by_name("Joe")

The alternative way to use this to pass your own block:

Artist.finder(name: :first_by_name){|pl, ds| ds.where(name: pl.arg).limit(1)}

Note that if you pass your own block, you are responsible for manually setting limits if necessary (as shown above).

Options:

:arity

When using a symbol method name, this specifies the arity of the method. This should be used if if the method accepts an arbitrary number of arguments, or the method has default argument values. Note that if the method is defined as a dataset method, the class method Sequel creates accepts an arbitrary number of arguments, so you should use this option in that case. If you want to handle multiple possible arities, you need to call the finder method multiple times with unique :arity and :name methods each time.

:name

The name of the method to create. This must be given if you pass a block. If you use a symbol, this defaults to the symbol prefixed by the type.

:mod

The module in which to create the finder method. Defaults to the singleton class of the model.

:type

The type of query to run. Can be :first, :each, :all, or :get, defaults to :first.

Caveats:

This doesn’t handle all possible cases. For example, if you have a method such as:

def Artist.by_name(name)
  name ? where(name: name) : exclude(name: nil)
end

Then calling a finder without an argument will not work as you expect.

Artist.finder :by_name
Artist.by_name(nil).first
# WHERE (name IS NOT NULL)
Artist.first_by_name(nil)
# WHERE (name IS NULL)

See Dataset::PlaceholderLiteralizer for additional caveats. Note that if the model’s dataset does not support placeholder literalizers, you will not be able to use this method.



103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
 
# File 'lib/sequel/plugins/finder.rb', line 103

def finder(meth=OPTS, opts=OPTS, &block)
  if block
    raise Error, "cannot pass both a method name argument and a block of Model.finder" unless meth.is_a?(Hash)
    raise Error, "cannot pass two option hashes to Model.finder" unless opts.equal?(OPTS)
    opts = meth
    raise Error, "must provide method name via :name option when passing block to Model.finder" unless meth_name = opts[:name]
  end

  type = opts.fetch(:type, :first)
  unless prepare = opts[:prepare]
    raise Error, ":type option to Model.finder must be :first, :all, :each, or :get" unless FINDER_TYPES.include?(type)
  end
  limit1 = type == :first || type == :get
  meth_name ||= opts[:name] || :"#{type}_#{meth}"

  argn = lambda do |model|
    if arity = opts[:arity]
      arity
    else
      method = block || model.method(meth)
      (method.arity < 0 ? method.arity.abs - 1 : method.arity)
    end
  end

  loader_proc = if prepare
    proc do |model|
      args = prepare_method_args('$a', argn.call(model))
      ds = if block
        model.instance_exec(*args, &block)
      else
        model.public_send(meth, *args)
      end
      ds = ds.limit(1) if limit1
      model_name = model.name
      if model_name.to_s.empty?
        model_name = model.object_id
      else
        model_name = model_name.gsub(/\W/, '_')
      end
      ds.prepare(type, :"#{model_name}_#{meth_name}")
    end
  else
    proc do |model|
      n = argn.call(model)
      block ||= lambda do |pl, model2|
        args = (0...n).map{pl.arg}
        ds = model2.public_send(meth, *args)
        ds = ds.limit(1) if limit1
        ds
      end

      model.dataset.placeholder_literalizer_class.loader(model, &block) 
    end
  end

  @finder_loaders[meth_name] = loader_proc
  mod = opts[:mod] || singleton_class
  if prepare
    def_prepare_method(mod, meth_name)
  else
    def_finder_method(mod, meth_name, type)
  end
end

#freeze ⇒ Object 



167
168
169
170
171
172
 
# File 'lib/sequel/plugins/finder.rb', line 167

def freeze
  @finder_loaders.freeze
  @finder_loaders.each_key{|k| finder_for(k)} if @dataset
  @finders.freeze
  super
end

#prepared_finder(meth = OPTS, opts = OPTS, &block) ⇒ Object

Similar to finder, but uses a prepared statement instead of a placeholder literalizer. This makes the SQL used static (cannot vary per call), but allows binding argument values instead of literalizing them into the SQL query string.

If a block is used with this method, it is instance_execed by the model, and should accept the desired number of placeholder arguments.

The options are the same as the options for finder, with the following exception:

:type

Specifies the type of prepared statement to create



185
186
187
188
189
190
191
192
193
 
# File 'lib/sequel/plugins/finder.rb', line 185

def prepared_finder(meth=OPTS, opts=OPTS, &block)
  if block
    raise Error, "cannot pass both a method name argument and a block of Model.finder" unless meth.is_a?(Hash)
    meth = meth.merge(:prepare=>true)
  else
    opts = opts.merge(:prepare=>true)
  end
  finder(meth, opts, &block)
end