Fix error when users table does not exist (#21482)

* Fix error when users table does not exist

In multitenant context, when schema is switched to and the tables are
not created yet, getting `User.current` will fail with

    ActiveRecord::StatementInvalid:"PG::UndefinedTable: ERROR:  relation \"users\" does not exist" [...]

To prevent it, check if the table exists first and return `nil` if not.

* Avoid logging "slow sql" for database creation

* Better performance for handling unexisting users table

Checking multiple times the users table existence when something is
logged is probably a bad idea. Better rescue errors.

Also cache the return value of `#current_user` to call the method only
once.

config/initializers/log_slow_sql_queries.rb

@@ -42,8 +42,8 @@ Rails.application.configure do
       # Skip transaction that may be blocked
       next if data[:sql].match?(/BEGIN|COMMIT/)
 
-      # Skip tenant creation (load dump)
-      next if data[:sql][..120].include?("Dumped by pg_dump")
+      # Skip tenant creation (load dump sql which is around 300kB)
+      next if data[:sql][..120].include?("Dumped by pg_dump") || data[:sql].size > 200_000
 
       # Skip smaller durations
       duration = ((finish - start) * 1000).round(4)

lib/open_project/logging/log_delegator.rb

@@ -5,7 +5,7 @@ module OpenProject
         ##
         # Consume a message and let it be handled
         # by all handlers
-        def log(exception, context = {})
+        def log(exception, context = {}) # rubocop:disable Metrics/AbcSize, Metrics/PerceivedComplexity
           # in case we're getting ActionController::Parameters
           context = if context.respond_to?(:to_unsafe_h)
                       context.to_unsafe_h
@@ -28,9 +28,11 @@ module OpenProject
 
           # Set current contexts
           context[:level] ||= context[:exception] ? :error : :info
-          context[:current_user] ||= User.current
+          if the_current_user = current_user
+            context[:current_user] ||= the_current_user
+          end
 
-          registered_handlers.values.each do |handler|
+          registered_handlers.each_value do |handler|
             handler.call message, context
           rescue StandardError => e
             Rails.logger.error "Failed to delegate log to #{handler.inspect}: #{e.inspect}\nMessage: #{message.inspect}"
@@ -103,6 +105,14 @@ module OpenProject
           extended = OpenProject::Logging.extend_payload!(payload, context)
           OpenProject::Logging.formatter.call extended
         end
+
+        def current_user
+          User.current
+        # Probably more performant to rescue "ActiveRecord::StatementInvalid: PG::UndefinedTable"
+        # than to check for table existence with `User.connection.data_source_exists?(User.table_name)`
+        rescue StandardError
+          nil
+        end
       end
     end
   end