When a class has a belongs_to or has_one relationship with dependent: :destroy
option enabled, objects of this class should not be deleted if it's dependents
cannot be deleted.

Example:

    class Parent
      has_one :child, dependent: :destroy
    end

    class Child
      belongs_to :parent, inverse_of: :child
      before_destroy { throw :abort }
    end

    c = Child.create
    p = Parent.create(child: c)

    p.destroy

    p.destroyed? # expected: false; actual: true;

Fixes #32022

This issue is caused by `@_trigger_update_callback` won't be updated due
to `_update_record` in `Locking::Optimistic` doesn't call `super` when
optimistic locking is enabled.

Now optimistic locking concern when updating is supported by
`_update_row` low level API, therefore overriding `_update_record` is no
longer necessary.

Removing the method just fix the issue.

Closes #29096.
Closes #29321.
Closes #30823.

Currently primary key value can not be updated if a record has a locking
column because of `_update_record` in `Locking::Optimistic` doesn't
respect `id_in_database` as primary key value unlike in `Persistence`.

And also, if a record has dirty primary key value, it may destroy any
other record by the lock version of dirty record itself.

When updating/destroying persisted records, it should identify
themselves by `id_in_database`, not by dirty primary key value.

Related to https://github.com/rails/rails/commit/d4eb0dc89ee6b476e2e10869dc282a96f956c6c7#r27830891

This reverts ignoring polymorphic error introduced at 02da8aea.

What the ignoring want to solve was caused by force eager loading
regardless of whether it is necessary, but it has been fixed by #29043.

The ignoring is now only causing a mismatch of `exists?` behavior with
`to_a`, `count`, etc. It should behave consistently.

This is an alternative of #29722, and follow up of #32048.

This does not change the current behavior, but makes it easier to modify
all polymorphic names consistently.

Since Rails 6 requires Ruby 2.4.1+.

Related to 948b9319

Prevent `ActiveRecord::FinderMethods#limited_ids_for` from using correct primary
key values even if `ORDER BY` columns include other table's primary key.

Fixes #28364.

See 948b9319 for context

Currently the place where we limit what gets sent to the database is in
the implementation for `partial_writes`. We should also be restricting
it to column names when partial writes are turned off.

Note that we're using `&` instead of just defaulting to
`self.class.column_names`, as the instance version of `attribute_names`
does not include attributes which are uninitialized (were not included
in the select clause)

Since #31895, build of 2.5 and AR combination failed.
https://travis-ci.org/rails/rails/jobs/346064349#L1638

It seems to be the reason that model is not loading properly, so I added
require. But I'm not sure if this is correct

This is an alternative of #29722, and revert of #29601 and a1fcbd97.

Currently, association creation and normal association finding doesn't
respect `store_full_sti_class`. But eager loading and preloading respect
the setting. This means that if set `store_full_sti_class = false`
(`true` by default), eager loading and preloading can not find
created polymorphic records.

Association creation and finding should work consistently.

* Add test case for open-ended range.
* Add test case for numeric range for string column.

BC dates are supported by both date and datetime types.

https://www.postgresql.org/docs/current/static/datatype-datetime.html

Since #1097, new datetime allows year zero as 1 BC, but new date does
not. It should be allowed even in new date consistently.

The values infinity and -infinity are supported by both date and
timestamp types.

https://www.postgresql.org/docs/current/static/datatype-datetime.html#DATATYPE-DATETIME-SPECIAL-TABLE

And also, it can not be known whether a value is infinity correctly
unless cast a value.

I've added `QueryAttribute#infinity?` to handle that case.

Closes #27585.

This reverts commit 16f279eb, reversing
changes made to 6c6a30a7.

The config can be named anything, not just default (although all
generated apps will be named default). We can't just delete configs that
don't have a database because that will break three-tier configs. Oh
well.

SQLServerAdapter (gem `activerecord-sqlserver-adapter`) uses square
brackets for quoting column names (e.g. `[id]`). Those brackets must not
be misinterpreted in regular expressions.

Failure:
Expected /SELECT [developers].[id].* FROM developers/ to match "SELECT [developers].[id], [developers].[name], [developers].[salary], [developers].[firm_id], [developers].[mentor_id], [developers].[created_at], [developers].[updated_at], [developers].[created_on], [developers].[updated_on] FROM developers".

Because of this default configuration we're constantly checking if the
database exists when looping through configurations. This is unnecessary
and we should just delete it before we need to loop through
configurations.

Fixes #32021.

This is an alternative of #31877 to fix #31876 caused by #28808.

This issue was caused by a combination of several loose implementation.

* finding automatic inverse association of polymorphic without context (caused by #28808)
* returning `klass` even if `polymorphic?` (exists before #28808)
* loose verification by `valid_inverse_reflection?` (exists before #28808)

This makes `klass` raise if `polymorphic?` not to be misused.
This issue will not happen unless polymorphic `klass` is misused.

Fixes #31876.
Closes #31877.

3acc5d6e was changed the order of scope evaluation from through scope to
the association's own scope to be prioritized over the through scope.
But the sorting order will be prioritized that is evaluated first. It is
unintentional effect, association scope's sorting order should be
prioritized as well.

Fixes #32008.

Closes #31998

Some places we can't remove because Ruby still don't have a method
equivalent to strip_heredoc to be called in an already existent string.

Add #create_or_find_by to lean on unique constraints

* Add Relation#pick as short-hand for single-value plucks

https://travis-ci.org/rails/rails/jobs/338338927#L1043

Related to daf15f58

Currently `_default_attributes` doesn't work unless `load_schema` is
called before.

The `MissingAttributeError` is caused by `reload_schema_from_cache` is
invoked by `serialize`.

I added `load_schema` in `_default_attributes` to `_default_attributes`
works without any dependency like `attribute_types` etc.

Closes #31905.

This can not expand an array of aggregated objects correctly, and is no
longer used internally since 159b21b5.

Follow up of #31724.

If `composed_of` objects have multiple mappings, array predicate handler
can not correctly handle the expanded condition.

We need to handle it like polymorphic association objects.