X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/b612ef0640ea45f03ad43ed4b124be1034d21071..32030bce1b67218c91a8ed2a0287ec973221c5f7:/services/api/lib/update_permissions.rb

diff --git a/services/api/lib/update_permissions.rb b/services/api/lib/update_permissions.rb
index d6e6537725..b7e5476404 100644
--- a/services/api/lib/update_permissions.rb
+++ b/services/api/lib/update_permissions.rb
@@ -8,6 +8,8 @@ REVOKE_PERM = 0
 CAN_MANAGE_PERM = 3
 
 def update_permissions perm_origin_uuid, starting_uuid, perm_level, edge_id=nil
+  return if Thread.current[:suppress_update_permissions]
+
   #
   # Update a subset of the permission table affected by adding or
   # removing a particular permission relationship (ownership or a
@@ -50,15 +52,22 @@ def update_permissions perm_origin_uuid, starting_uuid, perm_level, edge_id=nil
   # how the permissions are computed.
 
   if edge_id.nil?
+    # For changes of ownership, edge_id is starting_uuid.  In turns
+    # out most invocations of update_permissions are for changes of
+    # ownership, so make this parameter optional to reduce
+    # clutter.
+    # For permission links, the uuid of the link object will be passed in for edge_id.
     edge_id = starting_uuid
   end
 
   ActiveRecord::Base.transaction do
 
-    # "Conflicts with the ROW EXCLUSIVE, SHARE UPDATE EXCLUSIVE, SHARE
-    # ROW EXCLUSIVE, EXCLUSIVE, and ACCESS EXCLUSIVE lock modes. This
-    # mode protects a table against concurrent data changes."
-    ActiveRecord::Base.connection.execute "LOCK TABLE #{PERMISSION_VIEW} in SHARE MODE"
+    # "Conflicts with the ROW SHARE, ROW EXCLUSIVE, SHARE UPDATE
+    # EXCLUSIVE, SHARE, SHARE ROW EXCLUSIVE, EXCLUSIVE, and ACCESS
+    # EXCLUSIVE lock modes. This mode allows only concurrent ACCESS
+    # SHARE locks, i.e., only reads from the table can proceed in
+    # parallel with a transaction holding this lock mode."
+    ActiveRecord::Base.connection.execute "LOCK TABLE #{PERMISSION_VIEW} in EXCLUSIVE MODE"
 
     # Workaround for
     # BUG #15160: planner overestimates number of rows in join when there are more than 200 rows coming from CTE
@@ -109,6 +118,10 @@ as select * from compute_permission_subgraph($1, $2, $3, $4)
 
     ActiveRecord::Base.connection.exec_query "SET LOCAL enable_mergejoin to true;"
 
+    # Now that we have recomputed a set of permissions, delete any
+    # rows from the materialized_permissions table where (target_uuid,
+    # user_uuid) is not present or has perm_level=0 in the recomputed
+    # set.
     ActiveRecord::Base.connection.exec_delete %{
 delete from #{PERMISSION_VIEW} where
   target_uuid in (select target_uuid from #{temptable_perms}) and
@@ -119,10 +132,18 @@ delete from #{PERMISSION_VIEW} where
 },
                                               "update_permissions.delete"
 
+    # Now insert-or-update permissions in the recomputed set.  The
+    # WHERE clause is important to avoid redundantly updating rows
+    # that haven't actually changed.
     ActiveRecord::Base.connection.exec_query %{
 insert into #{PERMISSION_VIEW} (user_uuid, target_uuid, perm_level, traverse_owned)
   select user_uuid, target_uuid, val as perm_level, traverse_owned from #{temptable_perms} where val>0
-on conflict (user_uuid, target_uuid) do update set perm_level=EXCLUDED.perm_level, traverse_owned=EXCLUDED.traverse_owned;
+on conflict (user_uuid, target_uuid) do update
+set perm_level=EXCLUDED.perm_level, traverse_owned=EXCLUDED.traverse_owned
+where #{PERMISSION_VIEW}.user_uuid=EXCLUDED.user_uuid and
+      #{PERMISSION_VIEW}.target_uuid=EXCLUDED.target_uuid and
+       (#{PERMISSION_VIEW}.perm_level != EXCLUDED.perm_level or
+        #{PERMISSION_VIEW}.traverse_owned != EXCLUDED.traverse_owned);
 },
                                              "update_permissions.insert"
 
@@ -135,7 +156,7 @@ end
 
 def check_permissions_against_full_refresh
   # No-op except when running tests
-  return unless Rails.env == 'test' and !Thread.current[:no_check_permissions_against_full_refresh]
+  return unless Rails.env == 'test' and !Thread.current[:no_check_permissions_against_full_refresh] and !Thread.current[:suppress_update_permissions]
 
   # For checking correctness of the incremental permission updates.
   # Check contents of the current 'materialized_permission' table
@@ -186,6 +207,17 @@ def skip_check_permissions_against_full_refresh
   end
 end
 
+def batch_update_permissions
+  check_perm_was = Thread.current[:suppress_update_permissions]
+  Thread.current[:suppress_update_permissions] = true
+  begin
+    yield
+  ensure
+    Thread.current[:suppress_update_permissions] = check_perm_was
+    refresh_permissions
+  end
+end
+
 # Used to account for permissions that a user gains by having
 # can_manage on another user.
 #