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* Merge pull request #36665 from jmschneider/masterRafael Mendonça França2019-07-231-2/+2
|\ | | | | | | Make currency symbols optional for money column type in PostgreSQL
| * Make currency symbols optional for money column type in PostgreSQLJoel Schneider2019-07-121-2/+2
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* | Merge pull request #36706 from kirs/dedup-optimizer-hintsRyuta Kamizono2019-07-191-1/+1
|\ \ | | | | | | [ActiveRecord] Deduplicate optimizer hints
| * | [ActiveRecord] Deduplicate optimizer hintsKir Shatrov2019-07-191-1/+1
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* | | Include common commands in rails help outputTekin Suleyman2019-07-191-4/+4
|/ / | | | | | | | | | | With their descriptions commented out these commands were not included in the rails help command's output, which is a shame as they are useful, particularly during the development of more complex migrations.
* | Support beginless ranges in hash conditions.Josh Goodall2019-07-171-2/+2
| | | | | | | | | | | | | | | | | | Ruby 2.7 introduces beginless ranges (..value and ...value) and as with endless ranges we can turn these into inequalities, enabling expressions such as Order.where(created_at: ..1.year.ago) User.where(karma: ...0)
* | [ActiveRecord] Superclass for aborted queriesKir Shatrov2019-07-161-3/+7
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* | Add missing period [ci skip]Rafael Mendonça França2019-07-161-1/+1
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* | Raise specific exception on Mysql2::Error::TimeoutErrorKir Shatrov2019-07-162-1/+9
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* | active_support/core_ext/object/duplicable is not in use hereRyuta Kamizono2019-07-161-1/+0
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* active_support/deprecation has to be already required via ↵Akira Matsuda2019-07-123-4/+0
| | | | active_support/rails.rb
* No Woman, No tryAkira Matsuda2019-07-121-1/+0
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* Merge pull request #36647 from ↵Ryuta Kamizono2019-07-111-1/+1
|\ | | | | | | | | | | giraffate/fix_exists_with_distinct_and_offset_and_order_in_postgresql Fix `relation.exists?` with giving `distinct`, `offset` and `order` for joined table
| * Fix `relation.exists?` with giving `distinct`, `offset` and `order` for ↵Takayuki Nakata2019-07-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | joined table The error happens in PostgreSQL when using `relation.exists?` with `distinct`, `offset` and `order` for joined table. However, the error does not happen if either `distinct` or `offset` is removed. This behavior is confusing. Fixes #36632
* | Merge pull request #36653 from y-yagi/check_error_number_instead_of_messageYuji Yaginuma2019-07-112-2/+6
|\ \ | | | | | | MySQL: Check error number instead of a message
| * | MySQL: Check error number instead of a messageyuuji.yaginuma2019-07-112-2/+6
| |/ | | | | | | To be able to check regardless of locale.
* | Merge pull request #36645 from Shopify/arel-dispatch-cacheRyuta Kamizono2019-07-111-1/+1
|\ \ | | | | | | Share the Arel dispatch cache between connections
| * | Share the Arel dispatch cache between connectionsJean Boussier2019-07-101-1/+1
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* | Merge pull request #36637 from Shopify/share-quote-cacheRyuta Kamizono2019-07-114-7/+14
|\ \ | | | | | | Share the column and table name quote cache between connections
| * | Share the column and table name quote cache between connectionsJean Boussier2019-07-094-7/+14
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* | Merge pull request #36618 from engwan/fix-query-cache-with-shared-ar-connectionEileen M. Uchitelle2019-07-102-5/+9
|\ \ | |/ |/| Fix query cache when using shared connections
| * Fix query cache when using shared connectionsHeinrich Lee Yu2019-07-082-5/+9
| | | | | | | | | | Enables the query cache on the correct connection when shared connections across threads are enabled
* | Merge pull request #36612 from ↵Yuji Yaginuma2019-07-091-1/+1
|\ \ | | | | | | | | | | | | y-yagi/make_setup_works_when_using_with_locales_other_than_en Make "bin/setup" works when using PostgreSQL with locales other than en locale
| * | Make "bin/setup" works when using PostgreSQL with locales other than en localeyuuji.yaginuma2019-07-071-1/+1
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The PostgreSQL adapter uses an error message to determine if a database exists or not. https://github.com/rails/rails/blob/74ef67b16de67d2ae2f996e50a18a93aebf68fe6/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb#L49 However, this message is properly converted according to the locale. So this check does not work correctly for non-en locales. As a result, `db:prepare` cannot correctly determine if a database exists, and `bin/setup`, which depends on the task, does not work correctly if the database does not exist. It checks to exist if the "does not exist" exists, but that message is also used in other error messages(e.g. "role does not exist"). So cannot check correctly also in en locale. https://github.com/postgres/postgres/blob/master/src/backend/po/ja.po#L10542 It would be fine could check the status, but in my understanding, when a connecting fails, only the status `CONNECTION_BAD` be used, and it seems that details cannot be checked. https://www.postgresql.org/docs/11/libpq-status.html#LIBPQ-PQSTATUS I fixed to check whether the error message contains a database name. This is probably not accurate but can check it better now.
* | Merge branch 'master' into add_database_exist_methodGuillermo Iguaran2019-07-0821-37/+176
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| * | When DATABASE_URL is specified don't trample envs that use a url: keyWill Jessop2019-07-081-5/+5
| | | | | | | | | | | | fixes #36610
| * | Do not use aliases in GROUP BY clauseRyuta Kamizono2019-07-081-1/+1
| |/ | | | | | | | | | | | | It appears that Oracle does not allow using aliases in GROUP BY clause unlike ORDER BY clause. Fixes #36613.
| * MySQL: Fix schema dumping `enum` and `set` columns correctlyRyuta Kamizono2019-07-052-2/+8
| | | | | | | | | | | | | | | | | | `enum` and `set` are typed cast as `:string`, but currently the `:string` type is incorrectly reused for schema dumping. A cast type on columns is not always the same with `sql_type`, this fixes schema dumping `enum` and `set` columns to use `sql_type` instead of `type` correctly.
| * Add "SCHEMA" to the query in `configure_connection` like as other adaptersRyuta Kamizono2019-06-281-1/+1
| | | | | | | | | | | | | | This makes to be able to ignore the query in `assert_queries` even if accidentally reconnected a connection. https://buildkite.com/rails/rails/builds/61917#4c49187a-3173-4d5c-8a8d-d65768f5bfc9/1000-1799
| * warning: instance variable @serial not initialized (#36556)utilum2019-06-281-0/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Introduced in bba7c63a663b073034f4c73f0d59655751694e5a Before: ``` $ TESTOPTS="-n=/test_yaml_dump_and_load/" bundle exec rake test:postgresql :scisors: ... :scisors: Using postgresql Run options: -n=/test_yaml_dump_and_load/ --seed 36896 /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized /home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15: warning: instance variable @serial not initialized . Finished in 0.195325s, 5.1197 runs/s, 35.8376 assertions/s. 1 runs, 7 assertions, 0 failures, 0 errors, 0 skips ``` Co-authored-by: Ryuta Kamizono <kamipo@gmail.com>
| * Fix broken url configseileencodes2019-06-271-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This PR is to fix #36559 but I also found other issues that haven't been reported. The check for `(config.size == 1 && config.values.all? { |v| v.is_a? String })` was naive. The only reason this passed was because we had tests that had single hash size configs, but that doesn't mean we don't want to create a hash config in other cases. So this now checks for `config["database"] || config["adapter"] || ENV["DATABASE_URL"]`. In the end for url configs we still get a UrlConfig but we need to pass through the HashConfig to create the right kind of UrlConfig. The UrlConfig's are really complex and I don't necessarily understand everything that's needed in order to act the same as Rails 5.2. I edited the connection handler test to demonstrate how the previous implementation was broken when checking config size. Now old and new tests pass so I think this is closer to 5.2. Fixes #36559
| * Load initial database.yml once, and warn if we can't create taskseileencodes2019-06-272-9/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For multiple databases we attempt to generate the tasks by reading the database.yml before the Rails application is booted. This means that we need to strip out ERB since it could be reading Rails configs. In some cases like https://github.com/rails/rails/issues/36540 the ERB is too complex and we can't overwrite with the DummyCompilier we used in https://github.com/rails/rails/pull/35497. For the complex causes we simply issue a warning that says we couldn't infer the database tasks from the database.yml. While working on this I decided to update the code to only load the database.yml once initially so that we avoid having to issue the same warning multiple times. Note that this had no performance impact in my testing and is merely for not having to save the error off somewhere. Also this feels cleaner. Note that this will not break running tasks that exist, it will just mean that tasks for multi-db like `db:create:other_db` will not be generated. If the database.yml is actually unreadable it will blow up during normal rake task calls. Fixes #36540
| * Merge pull request #36210 from ↵Rafael França2019-06-241-1/+1
| |\ | | | | | | | | | | | | vishaltelangre/raise-record-invalid-when-associations-fail-to-save-due-to-uniqueness-failure Fix: ActiveRecord::RecordInvalid is not raised when an associated record fails to #save! due to uniqueness validation failure
| | * Fix: ActiveRecord::RecordInvalid is not raised when an associated record ↵Vishal Telangre2019-05-101-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | fails to #save! due to uniqueness validation failure Add tests Fix tests failing due to introduction of uniquness rule added to Book model
| * | Schema Cache: extract deduplication commonalityKasper Timm Hansen2019-06-211-10/+15
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| * | Also deduplicate schema cache data when using the init_with interfaceJean Boussier2019-06-211-6/+6
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| * | Revert schema dumper to use strings rather than integerseileencodes2019-06-202-3/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | I think we should change this, but not in 6-0-stable since that's already in RC and I was trying to only make changes that won't require any app changes. This reverts a portion of https://github.com/rails/rails/pull/36439 that made all schema migration version numbers get dumped as an integer. While it doesn't _really_ matter it did change behavior. We should bring this back in 6.1 with a deprecation.
| * | Merge pull request #36518 from Shopify/drop-schema-cache-column-hashKasper Timm Hansen2019-06-191-8/+5
| |\ \ | | | | | | | | Stop serializing and parsing columns_hash in Active Record schema caches
| | * | Stop serializing and parsing columns_hash in Active Record schema cachesJean Boussier2019-06-191-8/+5
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| * | | Better error message for calling columns_hashGuilherme Mansur2019-06-192-0/+7
| |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When a record does not have a table name, as in the case for a record with `self.abstract_class = true` and no `self.table_name` set the error message raises a cryptic: "ActiveRecord::StatementInvalid: Could not find table ''" this patch now raises a new `TableNotSpecified Error` Fixes: #36274 Co-Authored-By: Eugene Kenny <elkenny@gmail.com>
| * | Merge pull request #35891 from Shopify/schema-cache-deduplicationKasper Timm Hansen2019-06-198-2/+105
| |\ \ | | | | | | | | Deduplicate various Active Record schema cache structures
| | * | Deduplicate various Active Record schema cache structuresJean Boussier2019-06-038-2/+105
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Real world database schemas contain a lot of duplicated data. Some column names like `id`, `created_at` etc can easily be repeated hundreds of times. Same for SqlTypeMetada, most database will contain only a limited number of possible combinations. This result in a lot of wasted memory. The idea here is to make these data sctructures immutable, use a registry to substitute similar instances with pre-existing ones.
| * | | Avoid redundant `time.getutc` call if it is already utc time objectRyuta Kamizono2019-06-181-5/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently `type.serialize` and `connection.{quote|type_cast}` for a time object always does `time.getutc` call regardless of whether it is already utc time object or not, that duplicated proccess (`connection.type_cast(type.serialize(time))`) allocates extra/useless time objects for each type casting. This avoids that redundant `time.getutc` call if it is already utc time object. In the case of a model has timestamps (`created_at` and `updated_at`), it avoids 6,000 time objects allocation for 1,000 times `model.save`. ```ruby ObjectSpace::AllocationTracer.setup(%i{path line type}) pp ObjectSpace::AllocationTracer.trace { 1_000.times { User.create } }.select { |k, _| k[0].end_with?("quoting.rb", "time_value.rb") } ``` Before (c104bfe424e6cebe9c8e85a38515327a6c88b1f8): ``` {["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 203, :T_ARRAY]=>[1004, 0, 778, 0, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 220, :T_STRING]=>[2, 0, 2, 1, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 209, :T_ARRAY]=>[8, 0, 8, 1, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 57, :T_ARRAY]=>[4, 0, 4, 1, 1, 0], ["~/rails/activemodel/lib/active_model/type/helpers/time_value.rb", 17, :T_DATA]=>[4000, 0, 3096, 0, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 120, :T_DATA]=>[2000, 0, 1548, 0, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 126, :T_STRING]=>[4000, 0, 3096, 0, 1, 0]} ``` After (this change): ``` {["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 203, :T_ARRAY]=>[1004, 0, 823, 0, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 220, :T_STRING]=>[2, 0, 2, 1, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 209, :T_ARRAY]=>[8, 0, 8, 1, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 57, :T_ARRAY]=>[4, 0, 4, 1, 1, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/abstract/quoting.rb", 126, :T_STRING]=>[2000, 0, 1638, 0, 1, 0]} ```
* | | | Add database_exists? method to connection adaptersGuilherme Mansur2019-06-174-0/+27
|/ / / | | | | | | | | | | | | | | | | | | | | | When SQLite connects it will silently create a database if the database does not exist. This behaviour causes different issues because of inconsistent behaviour between adapters: #36383, #32914. This commit adds a `database_exists?` method as a way to check the database without creating it. This is a stepping stone to fully resolving the above issues.
* | | PostgreSQL: Fix GROUP BY with ORDER BY virtual count attributeRyuta Kamizono2019-06-171-10/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | GROUP BY with virtual count attribute is invalid for almost all databases, but it is valid for PostgreSQL, and it had worked until Rails 5.2.2, so it is a regression for Rails 5.2.3 (caused by 311f001). I can't find perfectly solution for fixing this for now, but I would not like to break existing apps, so I decided to allow referencing virtual count attribute in ORDER BY clause when GROUP BY aggrigation (it partly revert the effect of 311f001) to fix the regression #36022. Fixes #36022.
* | | Remove unused `Arel::Attributes.for`Ryuta Kamizono2019-06-153-29/+1
| | | | | | | | | | | | `Arel::Attributes.for` is no longer used since https://github.com/rails/arel/pull/196.
* | | No allocation `Arel::Visitors::ToSql#visit`Ryuta Kamizono2019-06-154-33/+34
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Each `visit o, collector` allocates one extra array due to receiving args by splat array. https://github.com/rails/rails/blob/2c3332cc4c0fa77dbe2e13e8a792f80fbd8f4ad3/activerecord/lib/arel/visitors/visitor.rb#L27-L29 Currently 1,000 times `User.where(id: 1).to_sql` allocates 13,000 arrays in `visitor.accept`. This avoids receiving args by splat array, it makes `visitor.accept` no array allocation. ```ruby ObjectSpace::AllocationTracer.setup(%i{path line type}) pp ObjectSpace::AllocationTracer.trace { 1_000.times { User.where(id: 1).to_sql } }.select { |k, _| k[2] == :T_ARRAY && k[0].end_with?("visitor.rb", "to_sql.rb") } ``` Before (2c3332cc4c0fa77dbe2e13e8a792f80fbd8f4ad3): ``` {["~/rails/activerecord/lib/arel/visitors/to_sql.rb", 18, :T_ARRAY]=>[1000, 0, 0, 0, 0, 0], ["~/rails/activerecord/lib/active_record/connection_adapters/determine_if_preparable_visitor.rb", 11, :T_ARRAY]=>[1000, 0, 0, 0, 0, 0], ["~/rails/activerecord/lib/arel/visitors/visitor.rb", 12, :T_ARRAY]=>[1000, 0, 0, 0, 0, 0], ["~/rails/activerecord/lib/arel/visitors/to_sql.rb", 788, :T_ARRAY]=>[3000, 0, 0, 0, 0, 0], ["~/rails/activerecord/lib/arel/visitors/to_sql.rb", 794, :T_ARRAY]=>[3000, 0, 0, 0, 0, 0], ["~/rails/activerecord/lib/arel/visitors/to_sql.rb", 156, :T_ARRAY]=>[1000, 0, 0, 0, 0, 0], ["~/rails/activerecord/lib/arel/visitors/to_sql.rb", 443, :T_ARRAY]=>[1000, 0, 0, 0, 0, 0], ["~/rails/activerecord/lib/arel/visitors/to_sql.rb", 603, :T_ARRAY]=>[1000, 0, 0, 0, 0, 0], ["~/rails/activerecord/lib/arel/visitors/to_sql.rb", 611, :T_ARRAY]=>[1000, 0, 0, 0, 0, 0]} ``` After (this change): ``` {} ```
* | | Move while_preventing_writes from conn to handlereileencodes2019-06-143-17/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If we put the `while_preventing_writes` on the connection then the middleware that sends reads to the primary and ensures they can't write will not work. The `while_preventing_writes` will only be applied to the connection which it's called on - which in the case of the middleware is Ar::Base. This worked fine if you called it directly like `OtherDbConn.connection.while_preventing_writes` but Rails didn't have a way of knowing you wanted to call it on all the connections. The change here moves the `while_preventing_writes` method from the connection to the handler so that it can block writes to all queries for that handler. This will apply to all the connections associated with that handler.
* | | Merge pull request #36439 from ↵Eileen M. Uchitelle2019-06-146-32/+52
|\ \ \ | | | | | | | | | | | | | | | | eileencodes/move-schema-migration-to-migration-context Move SchemaMigration to migration_context
| * | | Move SchemaMigration to migration_contexteileencodes2019-06-146-32/+52
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This PR moves the `schema_migration` to `migration_context` so that we can access the `schema_migration` per connection. This does not change behavior of the SchemaMigration if you are using one database. This also does not change behavior of any public APIs. `Migrator` is private as is `MigrationContext` so we can change these as needed. We now need to pass a `schema_migration` to `Migrator` so that we can run migrations on the right connection outside the context of a rake task. The bugs this fixes were discovered while debugging the issues around the SchemaCache on initialization with multiple database. It was clear that `get_all_versions` wouldn't work without these changes outside the context of a rake task (because in the rake task we establish a connection and change AR::Base.connection to the db we're running on). Because the `SchemaCache` relies on the `SchemaMigration` information we need to make sure we store it per-connection rather than on ActiveRecord::Base. [Eileen M. Uchitelle & Aaron Patterson]