1 # Copyright (C) The Arvados Authors. All rights reserved.
3 # SPDX-License-Identifier: AGPL-3.0
5 PERMISSION_VIEW = "materialized_permissions"
6 TRASHED_GROUPS = "trashed_groups"
8 def refresh_permissions
9 ActiveRecord::Base.transaction do
10 ActiveRecord::Base.connection.execute("LOCK TABLE #{PERMISSION_VIEW}")
11 ActiveRecord::Base.connection.execute("DELETE FROM #{PERMISSION_VIEW}")
12 ActiveRecord::Base.connection.execute %{
13 INSERT INTO #{PERMISSION_VIEW}
14 select users.uuid, g.target_uuid, g.val, g.traverse_owned
15 from users, lateral search_permission_graph(users.uuid, 3) as g where g.val > 0
17 "refresh_permission_view.do"
22 ActiveRecord::Base.transaction do
23 ActiveRecord::Base.connection.execute("LOCK TABLE #{TRASHED_GROUPS}")
24 ActiveRecord::Base.connection.execute("DELETE FROM #{TRASHED_GROUPS}")
25 ActiveRecord::Base.connection.execute("INSERT INTO #{TRASHED_GROUPS} select * from compute_trashed()")
29 def update_permissions perm_origin_uuid, starting_uuid, perm_level
31 # Update a subset of the permission table affected by adding or
32 # removing a particular permission relationship (ownership or a
35 # perm_origin_uuid: This is the object that 'gets' the permission.
36 # It is the owner_uuid or tail_uuid.
38 # starting_uuid: The object we are computing permission for (or head_uuid)
40 # perm_level: The level of permission that perm_origin_uuid gets for starting_uuid.
42 # perm_level is a number from 0-3
46 # or call with perm_level=0 to revoke permissions
48 # check: for testing/debugging, compare the result of the
49 # incremental update against a full table recompute. Throws an
50 # error if the contents are not identical (ie they produce different
55 # Give a change in a specific permission relationship, we recompute
56 # the set of permissions (for all users) that could possibly be
57 # affected by that relationship. For example, if a project is
58 # shared with another user, we recompute all permissions for all
59 # projects in the hierarchy. This returns a set of updated
60 # permissions, which we stash in a temporary table.
62 # Then, for each user_uuid/target_uuid in the updated permissions
63 # result set we insert/update a permission row in
64 # materialized_permissions, and delete any rows that exist in
65 # materialized_permissions that are not in the result set or have
68 # see db/migrate/20200501150153_permission_table.rb for details on
69 # how the permissions are computed.
71 ActiveRecord::Base.transaction do
73 # "Conflicts with the ROW EXCLUSIVE, SHARE UPDATE EXCLUSIVE, SHARE
74 # ROW EXCLUSIVE, EXCLUSIVE, and ACCESS EXCLUSIVE lock modes. This
75 # mode protects a table against concurrent data changes."
76 ActiveRecord::Base.connection.execute "LOCK TABLE #{PERMISSION_VIEW} in SHARE MODE"
79 # BUG #15160: planner overestimates number of rows in join when there are more than 200 rows coming from CTE
80 # https://www.postgresql.org/message-id/152395805004.19366.3107109716821067806@wrigleys.postgresql.org
82 # For a crucial join in the compute_permission_subgraph() query, the
83 # planner mis-estimates the number of rows in a Common Table
84 # Expression (CTE, this is a subquery in a WITH clause) and as a
85 # result it chooses the wrong join order. The join starts with the
86 # permissions table because it mistakenly thinks
87 # count(materalized_permissions) < count(new computed permissions)
88 # when actually it is the other way around.
90 # Because of the incorrect join order, it choose the wrong join
91 # strategy (merge join, which works best when two tables are roughly
92 # the same size). As a workaround, we can tell it not to use that
93 # join strategy, this causes it to pick hash join instead, which
94 # turns out to be a bit better. However, because the join order is
95 # still wrong, we don't get the full benefit of the index.
97 # This is very unfortunate because it makes the query performance
98 # dependent on the size of the materalized_permissions table, when
99 # the goal of this design was to make permission updates scale-free
100 # and only depend on the number of permissions affected and not the
101 # total table size. In several hours of researching I wasn't able
102 # to find a way to force the correct join order, so I'm calling it
103 # here and I have to move on.
105 # This is apparently addressed in Postgres 12, but I developed &
106 # tested this on Postgres 9.6, so in the future we should reevaluate
107 # the performance & query plan on Postgres 12.
109 # https://git.furworks.de/opensourcemirror/postgresql/commit/a314c34079cf06d05265623dd7c056f8fa9d577f
111 # Disable merge join for just this query (also local for this transaction), then reenable it.
112 ActiveRecord::Base.connection.exec_query "SET LOCAL enable_mergejoin to false;"
114 temptable_perms = "temp_perms_#{rand(2**64).to_s(10)}"
115 ActiveRecord::Base.connection.exec_query %{
116 create temporary table #{temptable_perms} on commit drop
117 as select * from compute_permission_subgraph($1, $2, $3)
119 'update_permissions.select',
120 [[nil, perm_origin_uuid],
121 [nil, starting_uuid],
124 ActiveRecord::Base.connection.exec_query "SET LOCAL enable_mergejoin to true;"
126 ActiveRecord::Base.connection.exec_delete %{
127 delete from #{PERMISSION_VIEW} where
128 target_uuid in (select target_uuid from #{temptable_perms}) and
129 not exists (select 1 from #{temptable_perms}
130 where target_uuid=#{PERMISSION_VIEW}.target_uuid and
131 user_uuid=#{PERMISSION_VIEW}.user_uuid and
134 "update_permissions.delete"
136 ActiveRecord::Base.connection.exec_query %{
137 insert into #{PERMISSION_VIEW} (user_uuid, target_uuid, perm_level, traverse_owned)
138 select user_uuid, target_uuid, val as perm_level, traverse_owned from #{temptable_perms} where val>0
139 on conflict (user_uuid, target_uuid) do update set perm_level=EXCLUDED.perm_level, traverse_owned=EXCLUDED.traverse_owned;
141 "update_permissions.insert"
144 check_permissions_against_full_refresh
150 def check_permissions_against_full_refresh
151 # No-op except when running tests
152 return unless Rails.env == 'test' and !Thread.current[:no_check_permissions_against_full_refresh]
154 # For checking correctness of the incremental permission updates.
155 # Check contents of the current 'materialized_permission' table
156 # against a from-scratch permission refresh.
158 q1 = ActiveRecord::Base.connection.exec_query %{
159 select user_uuid, target_uuid, perm_level, traverse_owned from #{PERMISSION_VIEW}
160 order by user_uuid, target_uuid
161 }, "check_permissions_against_full_refresh.permission_table"
163 q2 = ActiveRecord::Base.connection.exec_query %{
164 select users.uuid as user_uuid, g.target_uuid, g.val as perm_level, g.traverse_owned
165 from users, lateral search_permission_graph(users.uuid, 3) as g where g.val > 0
166 order by users.uuid, target_uuid
167 }, "check_permissions_against_full_refresh.full_recompute"
169 if q1.count != q2.count
170 puts "Didn't match incremental+: #{q1.count} != full refresh-: #{q2.count}"
173 if q1.count > q2.count
174 q1.each_with_index do |r, i|
176 puts "+#{r}\n-#{q2[i]}"
181 q2.each_with_index do |r, i|
183 puts "+#{q1[i]}\n-#{r}"
190 def skip_check_permissions_against_full_refresh
191 check_perm_was = Thread.current[:no_check_permissions_against_full_refresh]
192 Thread.current[:no_check_permissions_against_full_refresh] = true
196 Thread.current[:no_check_permissions_against_full_refresh] = check_perm_was