/usr/lib/ruby/vendor_ruby/sequel/extensions/null_dataset.rb is in ruby-sequel 4.15.0-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 | # The null_dataset extension adds the Dataset#nullify method, which
# returns a cloned dataset that will never issue a query to the
# database. It implements the null object pattern for datasets.
#
# The most common usage is probably in a method that must return
# a dataset, where the method knows the dataset shouldn't return
# anything. With standard Sequel, you'd probably just add a
# WHERE condition that is always false, but that still results
# in a query being sent to the database, and can be overridden
# using #unfiltered, the OR operator, or a UNION.
#
# Usage:
#
# ds = DB[:items].nullify.where(:a=>:b).select(:c)
# ds.sql # => "SELECT c FROM items WHERE (a = b)"
# ds.all # => [] # no query sent to the database
#
# Note that there is one case where a null dataset will sent
# a query to the database. If you call #columns on a nulled
# dataset and the dataset doesn't have an already cached
# version of the columns, it will create a new dataset with
# the same options to get the columns.
#
# This extension uses Object#extend at runtime, which can hurt performance.
#
# To add the nullify method to a single dataset:
#
# ds = ds.extension(:null_dataset)
#
# To add the nullify method to all datasets on a single database:
#
# DB.extension(:null_dataset)
#
module Sequel
class Dataset
module Nullifiable
# Return a cloned nullified dataset.
def nullify
clone.nullify!
end
# Nullify the current dataset
def nullify!
extend NullDataset
end
end
module NullDataset
# Create a new dataset from the dataset (which won't
# be nulled) to get the columns if they aren't already cached.
def columns
@columns ||= db.dataset.clone(@opts).columns
end
# Return 0 without sending a database query.
def delete
0
end
# Return self without sending a database query, never yielding.
def each
self
end
# Return nil without sending a database query, never yielding.
def fetch_rows(sql)
nil
end
# Return nil without sending a database query.
def insert(*)
nil
end
# Return nil without sending a database query.
def truncate
nil
end
# Return 0 without sending a database query.
def update(v=OPTS)
0
end
protected
# Return nil without sending a database query.
def _import(columns, values, opts)
nil
end
private
# Just in case these are called directly by some internal code,
# make them noops. There's nothing we can do if the db
# is accessed directly to make a change, though.
(%w'_ddl _dui _insert' << '').each do |m|
class_eval("private; def execute#{m}(sql, opts=OPTS) end", __FILE__, __LINE__)
end
end
end
Dataset.register_extension(:null_dataset, Dataset::Nullifiable)
end
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