forked from mislav/will_paginate
/
finder.rb
256 lines (223 loc) · 10.7 KB
/
finder.rb
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require 'will_paginate/core_ext'
module WillPaginate
# A mixin for ActiveRecord::Base. Provides +per_page+ class method
# and hooks things up to provide paginating finders.
#
# Find out more in WillPaginate::Finder::ClassMethods
#
module Finder
def self.included(base)
base.extend ClassMethods
class << base
alias_method_chain :method_missing, :paginate
# alias_method_chain :find_every, :paginate
define_method(:per_page) { 30 } unless respond_to?(:per_page)
end
end
# = Paginating finders for ActiveRecord models
#
# WillPaginate adds +paginate+, +per_page+ and other methods to
# ActiveRecord::Base class methods and associations. It also hooks into
# +method_missing+ to intercept pagination calls to dynamic finders such as
# +paginate_by_user_id+ and translate them to ordinary finders
# (+find_all_by_user_id+ in this case).
#
# In short, paginating finders are equivalent to ActiveRecord finders; the
# only difference is that we start with "paginate" instead of "find" and
# that <tt>:page</tt> is required parameter:
#
# @posts = Post.paginate :all, :page => params[:page], :order => 'created_at DESC'
#
# In paginating finders, "all" is implicit. There is no sense in paginating
# a single record, right? So, you can drop the <tt>:all</tt> argument:
#
# Post.paginate(...) => Post.find :all
# Post.paginate_all_by_something => Post.find_all_by_something
# Post.paginate_by_something => Post.find_all_by_something
#
# == The importance of the <tt>:order</tt> parameter
#
# In ActiveRecord finders, <tt>:order</tt> parameter specifies columns for
# the <tt>ORDER BY</tt> clause in SQL. It is important to have it, since
# pagination only makes sense with ordered sets. Without the <tt>ORDER
# BY</tt> clause, databases aren't required to do consistent ordering when
# performing <tt>SELECT</tt> queries; this is especially true for
# PostgreSQL.
#
# Therefore, make sure you are doing ordering on a column that makes the
# most sense in the current context. Make that obvious to the user, also.
# For perfomance reasons you will also want to add an index to that column.
module ClassMethods
# This is the main paginating finder.
#
# == Special parameters for paginating finders
# * <tt>:page</tt> -- REQUIRED, but defaults to 1 if false or nil
# * <tt>:per_page</tt> -- defaults to <tt>CurrentModel.per_page</tt> (which is 30 if not overridden)
# * <tt>:total_entries</tt> -- use only if you manually count total entries
# * <tt>:count</tt> -- additional options that are passed on to +count+
# * <tt>:finder</tt> -- name of the ActiveRecord finder used (default: "find")
#
# All other options (+conditions+, +order+, ...) are forwarded to +find+
# and +count+ calls.
def paginate(*args, &block)
options = args.pop
page, per_page, total_entries = wp_parse_options(options)
finder = (options[:finder] || 'find').to_s
if finder == 'find'
# an array of IDs may have been given:
total_entries ||= (Array === args.first and args.first.size)
# :all is implicit
args.unshift(:all) if args.empty?
end
WillPaginate::Collection.create(page, per_page, total_entries) do |pager|
count_options = options.except :page, :per_page, :total_entries, :finder
find_options = count_options.except(:count).update(:offset => pager.offset, :limit => pager.per_page)
args << find_options
# @options_from_last_find = nil
pager.replace send(finder, *args, &block)
# magic counting for user convenience:
pager.total_entries = wp_count(count_options, args, finder) unless pager.total_entries
end
end
# Iterates through all records by loading one page at a time. This is useful
# for migrations or any other use case where you don't want to load all the
# records in memory at once.
#
# It uses +paginate+ internally; therefore it accepts all of its options.
# You can specify a starting page with <tt>:page</tt> (default is 1). Default
# <tt>:order</tt> is <tt>"id"</tt>, override if necessary.
#
# See {Faking Cursors in ActiveRecord}[http://weblog.jamisbuck.org/2007/4/6/faking-cursors-in-activerecord]
# where Jamis Buck describes this and a more efficient way for MySQL.
def paginated_each(options = {}, &block)
options = { :order => 'id', :page => 1 }.merge options
options[:page] = options[:page].to_i
options[:total_entries] = 0 # skip the individual count queries
total = 0
begin
collection = paginate(options)
total += collection.each(&block).size
options[:page] += 1
end until collection.size < collection.per_page
total
end
# Wraps +find_by_sql+ by simply adding LIMIT and OFFSET to your SQL string
# based on the params otherwise used by paginating finds: +page+ and
# +per_page+.
#
# Example:
#
# @developers = Developer.paginate_by_sql ['select * from developers where salary > ?', 80000],
# :page => params[:page], :per_page => 3
#
# A query for counting rows will automatically be generated if you don't
# supply <tt>:total_entries</tt>. If you experience problems with this
# generated SQL, you might want to perform the count manually in your
# application.
#
def paginate_by_sql(sql, options)
WillPaginate::Collection.create(*wp_parse_options(options)) do |pager|
query = sanitize_sql(sql.dup)
original_query = query.dup
# add limit, offset
add_limit! query, :offset => pager.offset, :limit => pager.per_page
# perfom the find
pager.replace find_by_sql(query)
unless pager.total_entries
count_query = original_query.sub /\bORDER\s+BY\s+[\w`,\s]+$/mi, ''
count_query = "SELECT COUNT(*) FROM (#{count_query})"
unless ['oracle', 'oci'].include?(self.connection.adapter_name.downcase)
count_query << ' AS count_table'
end
# perform the count query
pager.total_entries = count_by_sql(count_query)
end
end
end
def respond_to?(method, include_priv = false) #:nodoc:
case method.to_sym
when :paginate, :paginate_by_sql
true
else
super(method.to_s.sub(/^paginate/, 'find'), include_priv)
end
end
protected
def method_missing_with_paginate(method, *args, &block) #:nodoc:
# did somebody tried to paginate? if not, let them be
unless method.to_s.index('paginate') == 0
return method_missing_without_paginate(method, *args, &block)
end
# paginate finders are really just find_* with limit and offset
finder = method.to_s.sub('paginate', 'find')
finder.sub!('find', 'find_all') if finder.index('find_by_') == 0
options = args.pop
raise ArgumentError, 'parameter hash expected' unless options.respond_to? :symbolize_keys
options = options.dup
options[:finder] = finder
args << options
paginate(*args, &block)
end
# Does the not-so-trivial job of finding out the total number of entries
# in the database. It relies on the ActiveRecord +count+ method.
def wp_count(options, args, finder)
excludees = [:count, :order, :limit, :offset, :readonly]
# we may be in a model or an association proxy
klass = (@owner and @reflection) ? @reflection.klass : self
# Use :select from scope if it isn't already present.
options[:select] = scope(:find, :select) unless options[:select]
if options[:select] and options[:select] =~ /^\s*DISTINCT\b/i
# Remove quoting and check for table_name.*-like statement.
if options[:select].gsub('`', '') =~ /\w+\.\*/
options[:select] = "DISTINCT #{klass.table_name}.#{klass.primary_key}"
end
else
excludees << :select # only exclude the select param if it doesn't begin with DISTINCT
end
# count expects (almost) the same options as find
count_options = options.except *excludees
# merge the hash found in :count
# this allows you to specify :select, :order, or anything else just for the count query
count_options.update options[:count] if options[:count]
# forget about includes if they are irrelevant (Rails 2.1)
if count_options[:include] and
klass.private_methods.include?('references_eager_loaded_tables?') and
!klass.send(:references_eager_loaded_tables?, count_options)
count_options.delete :include
end
# we may have to scope ...
counter = Proc.new { count(count_options) }
count = if finder.index('find_') == 0 and klass.respond_to?(scoper = finder.sub('find', 'with'))
# scope_out adds a 'with_finder' method which acts like with_scope, if it's present
# then execute the count with the scoping provided by the with_finder
send(scoper, &counter)
elsif match = /^find_(all_by|by)_([_a-zA-Z]\w*)$/.match(finder)
# extract conditions from calls like "paginate_by_foo_and_bar"
attribute_names = extract_attribute_names_from_match(match)
conditions = construct_attributes_from_arguments(attribute_names, args)
with_scope(:find => { :conditions => conditions }, &counter)
else
counter.call
end
count.respond_to?(:length) ? count.length : count
end
def wp_parse_options(options) #:nodoc:
raise ArgumentError, 'parameter hash expected' unless options.respond_to? :symbolize_keys
options = options.symbolize_keys
raise ArgumentError, ':page parameter required' unless options.key? :page
if options[:count] and options[:total_entries]
raise ArgumentError, ':count and :total_entries are mutually exclusive'
end
page = options[:page] || 1
per_page = options[:per_page] || self.per_page
total = options[:total_entries]
[page, per_page, total]
end
private
# def find_every_with_paginate(options)
# @options_from_last_find = options
# find_every_without_paginate(options)
# end
end
end
end