PostgreSQL: Ensure the database time zone matches Ruby's time zone

[kamipo]

This restores bf6661c (reverts 7a7c608).

If AR::Base.default_timezone = :local, incorrect value will be saved
unless the database time zone matches Ruby's time zone.

[pixeltrix]

Since TZ can be set via ENV how does that affect things? Obviously this affects the related MySQL PR too.

[kamipo]

Loading development environment (Rails 5.1.0.beta1)
irb(main):001:0> conn = ActiveRecord::Base.connection
=> #<ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x007fc602edbe60 @transaction_manager=#<ActiveRecord::ConnectionAdapters::TransactionManager:0x007fc602ec10d8 @stack=[], @connection=#<ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x007fc602edbe60 ...>>, @query_cache={}, @query_cache_enabled=false, @connection=#<SQLite3::Database:0x007fc602ee0118 @tracefunc=nil, @authorizer=nil, @encoding=#<Encoding:UTF-8>, @busy_handler=nil, @collations={}, @functions={}, @results_as_hash=true, @type_translation=nil, @readonly=false>, @owner=#<Thread:0x007fc60287f3a0 run>, @instrumenter=#<ActiveSupport::Notifications::Instrumenter:0x007fc60706a728 @id="9d283cffef99e245098c", @notifier=#<ActiveSupport::Notifications::Fanout:0x007fc602a78558 @subscribers=[#<ActiveSupport::Notifications::Fanout::Subscribers::Evented:0x007fc606088828 @pattern="sql.active_record", @delegate=#<ActiveRecord::LogSubscriber:0x007fc606088b70 @queue_key="ActiveRecord::LogSubscriber-70244240737720", @patterns=["sql.active_record"]>, @can_publish=false>, #<ActiveSupport::Notifications::Fanout::Subscribers::Evented:0x007fc603583560 @pattern="logger.action_view", @delegate=#<ActionView::LogSubscriber:0x007fc6035839e8 @root=nil, @queue_key="ActionView::LogSubscriber-70244218182900", @patterns=["logger.action_view", "render_collection.action_view", "render_partial.action_view", "render_template.action_view"]>, @can_publish=false>, #<ActiveSupport::Notifications::Fanout::Subscribers::Evented:0x007fc603583178 @pattern="render_collection.action_view", @delegate=#<ActionView::LogSubscriber:0x007fc6035839e8 @root=nil, @queue_key="ActionView::LogSubscriber-70244218182900", @patterns=["logger.action_view", "render_collection.action_view", "render_partial.action_view", "render_template.action_view"]>, @can_publish=false>, #<ActiveSupport::Notifications::Fanout::Subscribers::Evented:0x007fc603582de0 @pattern="render_partial.action_view", @delegate=#<ActionView::LogSubscriber:0x007fc6035839e8 @root=nil, @queue_key="ActionView::LogSubscriber-70244218182900", @patterns=["logger.action_view", "render_collection.action_view", "render_partial.action_view", "render_template.action_view"]>, @can_publish=false>, #<ActiveSupport::Notifications::Fanout::Subscribers::Evented:0x007fc603582958 @pattern="render_template.action_view", @delegate=#<ActionView::LogSubscriber:0x007fc6035839e8 @root=nil, @queue_key="ActionView::LogSubscriber-70244218182900", @patterns=["logger.action_view", "render_collection.action_view", "render_partial.action_view", "render_template.action_view"]>, @can_publish=false>, #<ActiveSupport::Notifications::Fanout::Subscribers::Evented:0x007fc606404178 @pattern="sql.active_record", @delegate=#<ActiveRecord::ExplainSubscriber:0x007fc6064041f0>, @can_publish=false>], @listeners_for=#<Concurrent::Map:0x007fc602a78468 entries=2 default_proc=nil>, @_mutex=#<Thread::Mutex:0x007fc602a78058>>>, @logger=#<ActiveSupport::Logger:0x007fc602b6a470 @progname=nil, @level=0, @default_formatter=#<Logger::Formatter:0x007fc602b6a3f8 @datetime_format=nil>, @formatter=#<ActiveSupport::Logger::SimpleFormatter:0x007fc60350a728 @datetime_format=nil, @thread_key="activesupport_tagged_logging_tags:70244217934740">, @logdev=#<Logger::LogDevice:0x007fc602b6a3a8 @shift_size=nil, @shift_age=nil, @filename=nil, @dev=#<File:/Users/kamipo/work/issue_25174/log/development.log>, @mon_owner=nil, @mon_count=0, @mon_mutex=#<Thread::Mutex:0x007fc602b6a358>>, @local_levels=#<Concurrent::Map:0x007fc602b6a2b8 entries=0 default_proc=nil>>, @config={:adapter=>"sqlite3", :pool=>5, :timeout=>5000, :database=>"/Users/kamipo/work/issue_25174/db/development.sqlite3"}, @pool=#<ActiveRecord::ConnectionAdapters::ConnectionPool:0x007fc60706a430 @mon_owner=nil, @mon_count=0, @mon_mutex=#<Thread::Mutex:0x007fc60706a318>, @query_cache_enabled=#<Concurrent::Map:0x007fc60706a2f0 entries=0 default_proc=#<Proc:0x007fc60706a2a0@/Users/kamipo/work/issue_25174/vendor/bundle/ruby/2.3.0/gems/activerecord-5.1.0.beta1/lib/active_record/connection_adapters/abstract/query_cache.rb:27>>, @spec=#<ActiveRecord::ConnectionAdapters::ConnectionSpecification:0x007fc60706a8e0 @name="primary", @config={:adapter=>"sqlite3", :pool=>5, :timeout=>5000, :database=>"/Users/kamipo/work/issue_25174/db/development.sqlite3"}, @adapter_method="sqlite3_connection">, @checkout_timeout=5, @reaper=#<ActiveRecord::ConnectionAdapters::ConnectionPool::Reaper:0x007fc60706a228 @pool=#<ActiveRecord::ConnectionAdapters::ConnectionPool:0x007fc60706a430 ...>, @frequency=nil>, @size=5, @thread_cached_conns=#<Concurrent::Map:0x007fc60706a1d8 entries=1 default_proc=nil>, @connections=[#<ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x007fc602edbe60 ...>], @automatic_reconnect=true, @now_connecting=0, @threads_blocking_new_connections=0, @available=#<ActiveRecord::ConnectionAdapters::ConnectionPool::ConnectionLeasingQueue:0x007fc60706a138 @lock=#<ActiveRecord::ConnectionAdapters::ConnectionPool:0x007fc60706a430 ...>, @cond=#<MonitorMixin::ConditionVariable:0x007fc60706a0e8 @monitor=#<ActiveRecord::ConnectionAdapters::ConnectionPool:0x007fc60706a430 ...>, @cond=#<Thread::ConditionVariable:0x007fc60706a0c0>>, @num_waiting=0, @queue=[]>, @lock_thread=false>, @schema_cache=#<ActiveRecord::ConnectionAdapters::SchemaCache:0x007fc602ec0f98 @connection=#<ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x007fc602edbe60 ...>, @columns={}, @columns_hash={}, @primary_keys={}, @data_sources={}>, @quoted_table_names={}, @quoted_column_names={}, @visitor=#<Arel::Visitors::SQLite:0x007fc602ec0e80 @dispatch={}, @connection=#<ActiveRecord::ConnectionAdapters::SQLite3Adapter:0x007fc602edbe60 ...>>, @lock=#<Monitor:0x007fc602ec0de0 @mon_owner=nil, @mon_count=0, @mon_mutex=#<Thread::Mutex:0x007fc602ec0d40>>, @prepared_statements=true, @active=nil, @statements=#<ActiveRecord::ConnectionAdapters::SQLite3Adapter::StatementPool:0x007fc602ec0ca0 @cache={}, @statement_limit=1000>>
irb(main):002:0> type = ActiveRecord::Type.lookup(:datetime)
=> #<ActiveRecord::Type::DateTime:0x007fc604045fe8 @precision=nil, @scale=nil, @limit=nil>
irb(main):003:0> time = Time.current
=> Sun, 12 Mar 2017 18:10:08 UTC +00:00
irb(main):004:0> ActiveRecord::Base.default_timezone = :utc
=> :utc
irb(main):005:0> ENV['TZ'] = "America/New_York"
=> "America/New_York"
irb(main):006:0> conn.type_cast(type.serialize(time))
=> "2017-03-12 18:10:08.666901"
irb(main):007:0> ActiveRecord::Base.default_timezone = :local
=> :local
irb(main):008:0> conn.type_cast(type.serialize(time))
=> "2017-03-12 14:10:08.666901"

If AR::Base.default_timezone = :utc, conn.type_cast(type.serialize(time)) generates "2017-03-12 18:10:08.666901". Then database regard the time as UTC time.

But if AR::Base.default_timezone = :local, conn.type_cast(type.serialize(time)) generates "2017-03-12 14:10:08.666901" as a local time (-04:00). If the database time zone is Japan (+09:00), it will deviate 13 hours.

The database time zone should match Ruby's time zone to avoid the issue.

[matthewd]

Couple of doubts:

1. I'm concerned this could change the interpretation of people's existing data, if they have a working setup.

2. It ignores DST (and any other offset changes that may occur after boot.. but DST is obviously the most likely to occur).

3. From memory, I thought the connection timezone was mostly relevant for timestamp without timezone. timestamptz refers to an unambiguous moment in time, regardless of TZ... if we're not round-tripping through that, it sounds more like a casting issue than a configuration one. 😕

[rails-bot]

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