These test cases tests exactly mutating loaded target.

This is not a test case.

Where appropriatei, prefer the more concise Regexp#match?,
String#include?, String#start_with?, or String#end_with?

Fixes #25732.

`AssociationQueryHandler` requires `association` initialized
`TableMetadata` even if `table_name == arel_table.name`.

Fixes #25689.

Actually schema dumper/creation supports composite primary key (#21614).
Therefore it should not show the warning about composite primary key in
connection adapter.

This change moves the warning to `AttributeMethods::PrimaryKey` and
suppress the warning for habtm join table.

Fixes #25388.

`construct_relation_for_association_calculations` pass a string value to
`construct_join_dependency` when setting a string value in `from`.
It should not pass a string value, but always `joins_values`.

Related #14834, #19452.

Fixes #24193.

Currently `exists?` does some hackery where it assumes that we can join
onto anything that we passed to `eager_load` or `includes`, which
doesn't work if we are joining onto a polymorphic association.

Actually figuring out if we want to include something would require
knowledge deep within the join dependency module, which is hard to pull
up. The simplest solution is just to pass a flag down that says we're
not actually going to try to eager load any of the data. It's not the
solution I'd like, but that code really needs to be untangled before we
can do much with it.

This is another attempt at 6d5b1fdf which should address the concerns
that led to reverting it in 4ecabed2.

Fixes #25128

Ruby 2.4 unifies Fixnum and Bignum into Integer: https://bugs.ruby-lang.org/issues/12005

* Forward compat with new unified Integer class in Ruby 2.4+.
* Backward compat with separate Fixnum/Bignum in Ruby 2.2 & 2.3.
* Drops needless Fixnum distinction in docs, preferring Integer.

The error message that we give today makes this error difficult to debug
if you receive it. I have no clue why we're printing the object ID of
the class (the commit doesn't give context), but I've left it as it was
deliberate.

* Fix undefined method `owners' for NullPreloader:Class

Fixing undefined method `owners' for
ActiveRecord::Associations::Preloader::NullPreloader:Class

* Use Ruby 1.9 hash format

Use Ruby 1.9 hash format

#24192

[Rafael Mendonça França + Ladislav Smola]

Closes #23934.

This is a forward port of ac832a43

Previously the scope of all associations with extensions were wrapped in
an instance dependent proc. This made it impossible to preload such
associations.

When the `source_type` option is passed to a has_many through, the
resulting `Reflection` will be an instance of `PolymorphicReflection`
and not `ThroughReflection`, meaning that it will ignore the scopes that
it needs to apply from the through reflections. This adds an additional
delegation call to remedy this. I've been finding the reflection code
completely impenetrable lately, it could use some major love.

Fixes #22726

habtm join tables commonly have two id columns and it's OK to make those
two id columns a primary key.  This commit eliminates the warnings for
join tables that have this setup.

  ManageIQ/manageiq#6713

Changed id-writer to save join table records based on association primary key

relations

This reverts commit 537ac7d6, reversing
changes made to 9c9c54ab.

Reason:
The way we preload associations will change the meaning of GROUP BY
operations. This is illustrated in the SQL generated by the added
test (failing on PG):

Association Load:
D, [2015-12-21T12:26:07.169920 #26969] DEBUG -- :   Post Load (0.7ms)  SELECT "posts".* FROM "posts" LEFT JOIN comments ON comments.post_id = posts.id WHERE "posts"."author_id" = $1 GROUP BY posts.id ORDER BY SUM(comments.tags_count)  [["author_id", 1]]

Preload:
D, [2015-12-21T12:26:07.128305 #26969] DEBUG -- :   Post Load (1.3ms)  SELECT "posts".* FROM "posts" LEFT JOIN comments ON comments.post_id = posts.id WHERE "posts"."author_id" IN (1, 2, 3) GROUP BY posts.id ORDER BY SUM(comments.tags_count)

Fixes problem when added `group()` in association scope was lost
in eager loaded association.

When same association is loaded in the model creation callback
The new object is inserted into association twice

If argument of `build_record` has key and value which is same as
default value of database, we should also except the key from
`create_scope` in `initialize_attributes`.
Because at first `build_record` initialize record object with argument
of `build_record`, then assign attributes derived from Association's scope.
In this case `record.changed` does not include the key, which value is
same as default value of database, so we should add the key to except list.

Fix #21893.

This assumes only one query was ever executed, but it appears to
sometimes be loading schema information. We can just look at the array
of queries, rather than the "first" one that was run

Before this commit, if
`ActiveRecord::Base.belongs_to_required_by_default` is set to `true`,
then creating a record through `has_and_belongs_to_many` fails with the
cryptic error message `Left side must exist`. This is because
`inverse_of` isn't working properly in this case, presumably since we're
doing trickery with anonymous classes in the middle.

Rather than following this rabbit hole to try and get `inverse_of` to
work in a case that we know is not publicly supported, we can just turn
off this validation to match the behavior of 4.2 and earlier.

This is part of a refactoring to make it easier to allow `order` to use
sanitize like just about everything else on relation. The deleted test
doesn't give any reasoning as to why passing `nil` to `order` needs to
be supported, and it's rather nonsensical. I can almost see allowing an
empty string being passed (though I'm tempted to just disallow it...)

This reverts commit 52439460.

This fixes an issue with the build where tests would fail on mysql and
postgresql due to different ordering.

This reverts commit 6dc6a0b1, reversing
changes made to ec94f00b.

This pull request broke the build.