Eagerly loaded collection and singular associations are ignored by the StatementCache, which causes errors when the queries they generate reference columns that were not eagerly loaded.

This commit skips the creation of the StatementCache as a fix for these scenarios.

We convert all other scopes to lambda's so it makes sense that we should
always returns a lambda on a ThroughReflection as well. This eliminates
the need to check if the scope is a Relation.

Remove chain from parameters, it's no longer needed since chain and i
are being passed via next_reflection

Change name of `reflection` to `owner_reflection` because of shadow
variable warning. The last reflection will always be the owner.

Added a few more methods on Module/Class to the dangerous class methods
blacklist. (Technically, allocate and new are already protected currently because
we happen to redefine them in the current implantation.)

Closes #16792

Warning looked like this:

```
/Users/senny/Projects/rails/activerecord/lib/active_record/associations/association_scope.rb:142: warning: shadowing outer local variable - reflection
```

[Joshua Cody & Yves Senn]

Closes #16757.

Prior to this patch schema loading rake tasks had the potential to leak a
connection to a different database. This had side-effects when rake tasks
operating on the current connection (like `db:seed`) were chained.

TableDefinition#column is not called from `add_column`.
Use TableDefinition#new_column_definition for column option handling.

Since 'drop table if exists' statement does not always work with
some databases such as Oracle.

Method .strip_heredoc is defined in
active_support/core_ext/string/strip.rb so we need to require it.

[fixes #16677]

We're seeing too many failures to believe otherwise.

This reverts commits bc116a55,
cbde413d,
bf0a6793, and
2440933f.

This breaks the two branches of the `if reflection.last` and `else`
to clearer see where the two methods can be refactored. Eventually
we hope to remove the need for these separated methods altogether.

Move the first branch outside the loop

This code doesn't need to be in the loop because it it always affects
the last chain. `get_bind_values` and `add_constraints` must match
in this context because `get_bind_values` is the caching of `add_constraints`

Use each_cons to remove need for `chain[i + 1]`

The `chain[i + 1]` is confusing because it's not immediately obvious
what it's trying to achieve. The use of `each_cons` makes it clear
we need to get the `next_reflection`.

Sets the connection collation to the database collation configured
in database.yml. Otherwise, `SET NAMES utf8mb4` will use the default
collation for that charset (utf8mb4_general_ci) when you may have chosen
a different collation, like utf8mb4_unicode_ci.

This only applies to literal string comparisons, not column values, so
it is unlikely to affect you.

so this assertion causes random test fail

When we are loading a component and we want to know its version, we are
actually not speaking about the constant but the library itself.

[ci skip]

[Godfrey Chan & Xavier Noria]

This fixes random test failure in migrator_test.rb

Asserting that the message contains "QUERY PLAN" is enough for the adapter's test.
The plan may vary according to number of tuples etc. but that's out of our concern.

This reverts commit 16fe1983, reversing
changes made to 4c81c8ce.

The call to `Model.reset_column_information` was to express the intent of the test.
`reset_column_information` itself can trigger SQL queries because it checks
for a tables existance. Let's move it outside of the block.

/cc @sgrif

Using heredoc would enforce line wrapping to whatever column width we decided to
use in the code, making it difficult for the users to read on some consoles.

This does make the source code read slightly worse and a bit more error-prone,
but this seems like a fair price to pay since the primary purpose for these
messages are for the users to read and the code will not stick around for too
long.

[ci skip]

This test would fail when executed after any test that calls fixtures(:binaries)

There exists some other test files that load :minivans fixtures but don't load :speedometers.
Loading :speedometers here prevents the following error when this test was run after such test:
CalculationsTest#test_should_group_by_association_with_non_numeric_foreign_key:
ActiveRecord::RecordNotFound: Couldn't find all Speedometers with 'speedometer_id': (ABC, s1) (found 1 results, but was looking for 2)

Dir.glob result must be already sorted anyway