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
|
# frozen-string-literal: true
#
# The select_remove extension adds select_remove for removing existing selected
# columns from a dataset. It's not part of Sequel core as it is rarely needed and has
# some corner cases where it can't work correctly.
#
# You can load this extension into specific datasets:
#
# ds = DB[:table]
# ds = ds.extension(:select_remove)
#
# Or you can load it into all of a database's datasets, which
# is probably the desired behavior if you are using this extension:
#
# DB.extension(:select_remove)
#
# Related module: Sequel::SelectRemove
#
module Sequel
module SelectRemove
# Remove columns from the list of selected columns. If any of the currently selected
# columns use expressions/aliases, this will remove selected columns with the given
# aliases. It will also remove entries from the selection that match exactly:
#
# # Assume columns a, b, and c in items table
# DB[:items] # SELECT * FROM items
# DB[:items].select_remove(:c) # SELECT a, b FROM items
# DB[:items].select(:a, Sequel[:b].as(:c), Sequel[:c].as(:b)).select_remove(:c) # SELECT a, c AS b FROM items
# DB[:items].select(:a, Sequel[:b][:c], Sequel[:c][:b]).select_remove(Sequel[:c][:b]) # SELECT a, b AS c FROM items
#
# Note that there are a few cases where this method may not work correctly:
#
# * This dataset joins multiple tables and does not have an existing explicit selection.
# In this case, the code will currently use unqualified column names for all columns
# the dataset returns, except for the columns given.
# * This dataset has an existing explicit selection containing an item that returns
# multiple database columns (e.g. Sequel[:table].*, Sequel.lit('column1, column2')). In this case,
# the behavior is undefined and this method should not be used.
#
# There may be other cases where this method does not work correctly, use it with caution.
def select_remove(*cols)
if (sel = @opts[:select]) && !sel.empty?
select(*(columns.zip(sel).reject{|c, s| cols.include?(c)}.map{|c, s| s} - cols))
else
select(*(columns - cols))
end
end
end
Dataset.register_extension(:select_remove, SelectRemove)
end
|
