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|
module ActiveRecord
###
# This class encapsulates a Result returned from calling +exec_query+ on any
# database connection adapter. For example:
#
# result = ActiveRecord::Base.connection.exec_query('SELECT id, title, body FROM posts')
# result # => #<ActiveRecord::Result:0xdeadbeef>
#
# # Get the column names of the result:
# result.columns
# # => ["id", "title", "body"]
#
# # Get the record values of the result:
# result.rows
# # => [[1, "title_1", "body_1"],
# [2, "title_2", "body_2"],
# ...
# ]
#
# # Get an array of hashes representing the result (column => value):
# result.to_hash
# # => [{"id" => 1, "title" => "title_1", "body" => "body_1"},
# {"id" => 2, "title" => "title_2", "body" => "body_2"},
# ...
# ]
#
# # ActiveRecord::Result also includes Enumerable.
# result.each do |row|
# puts row['title'] + " " + row['body']
# end
class Result
include Enumerable
IDENTITY_TYPE = Class.new { def type_cast(v); v; end }.new # :nodoc:
attr_reader :columns, :rows, :column_types
def initialize(columns, rows, column_types = {})
@columns = columns
@rows = rows
@hash_rows = nil
@column_types = column_types
end
def identity_type # :nodoc:
IDENTITY_TYPE
end
def column_type(name)
@column_types[name] || identity_type
end
def each
if block_given?
hash_rows.each { |row| yield row }
else
hash_rows.to_enum { @rows.size }
end
end
def to_hash
hash_rows
end
alias :map! :map
alias :collect! :map
# Returns true if there are no records.
def empty?
rows.empty?
end
def to_ary
hash_rows
end
def [](idx)
hash_rows[idx]
end
def last
hash_rows.last
end
def initialize_copy(other)
@columns = columns.dup
@rows = rows.dup
@column_types = column_types.dup
@hash_rows = nil
end
private
def hash_rows
@hash_rows ||=
begin
# We freeze the strings to prevent them getting duped when
# used as keys in ActiveRecord::Base's @raw_attributes hash
columns = @columns.map { |c| c.dup.freeze }
@rows.map { |row|
# In the past we used Hash[columns.zip(row)]
# though elegant, the verbose way is much more efficient
# both time and memory wise cause it avoids a big array allocation
# this method is called a lot and needs to be micro optimised
hash = {}
index = 0
length = columns.length
while index < length
hash[columns[index]] = row[index]
index += 1
end
hash
}
end
end
end
end
|
