Closes #7364.

Collection associations behave similar to Arrays. However there is no
way to prepend records. And to append one should use `<<`. Before this
patch `#append` and `#prepend` did not add the record to the loaded
association.

`#append` now behaves like `<<` and `#prepend` is not defined.

In an AR model a timestamptz attribute would return a ruby string and AR
tests did not check for any type casting.  Previous tests would pass
only because an assert_equal was being used on a Time.utc object, which
will parse the right side of the eq to a valid Time instance for
comparision.

switch to test instance of Time instead of ActiveSupport::TimeWithZone

Closes #9480.

We use `TableDefinition` for `#create_table` and `Table` for `#change_table`.
The PostgreSQL sepcifc types were only defined on `TableDefinition` so I
also added them to `Table`.

This reverts commit 408227d9, reversing
changes made to dca0b57d.

If the parent of a `belongs_to` record fails to be saved due to
validation errors, `touch` will be called on a new record, which causes
an exception (see https://github.com/rails/rails/pull/9320).

Example:

    class Owner < ActiveRecord::Base
      validates_presence_of :name
    end

    class Pet < ActiveRecord::Base
      belongs_to :owner, touch: true
    end

    pet = Pet.new(owner: Owner.new)

    # Before, this line would raise ActiveRecord::ActiveRecordError
    # "can not touch on a new record object"
    pet.save

It turns out this file is required in active_record.rb.

Fixes #9275.

When `#order` is called with a Symbol this patch will prepend the quoted_table_name.
Before the postgresql adapter failed to build queries containg a join and an order
with a symbol.

This expansion happens for all adapters.

to use it on an unpersisted object.

object that has not yet been persisted. This behavior follows the
precedent set by update_columns.

Taking the wise advice of @carlosantoniodasilva

closes #8663.

When preloading a hmt association there two possible scenarios:

1.) preload with 2 queries: first hm association, then hmt with id IN ()
2.) preload with join: hmt association is loaded with a join on the hm association

The bug was happening in scenario 1.) with a normal order clause on the hmt association.
The ordering was also applied when loading the hm association, which resulted in the error.

This patch only applies the ordering the the hm-relation if we are performing a join (2).
Otherwise the order will only appear in the second query (1).

We discussed that the auto explain feature is rarely used.
This PR removes only the automatic explain. You can still display
the explain output for any given relation using `ActiveRecord::Relation#explain`.

As a side-effect this should also fix the connection problem during
asset compilation (#9385). The auto explain initializer in the `ActiveRecord::Railtie`
forced a connection.

delete_all will call callbacks if depdent option is specified as
:destroy. This behavior is not very clear from the documetation and
hence issue #7832 was raised.

closes #7832

We should only type cast when we need to use.

Related to 4b005fb3

Closes #988.

As requested by @fxn
https://github.com/schuetzm/rails/commit/743d15bba182df80d003d205690ead988970299c#commitcomment-2661417

Explain that it doesn't create indices by default and
that it also has a block form.

When a table or a column is renamed related indexes kept their name. This will lead to confusing names. This patch renames related indexes when a column or a table is renamed. Only indexes with names generated by rails will be renamed. Indexes with custom names will not be renamed.

The function is now called has_arguments? so that it's easier to tell
that it's just checking to see if the args are blank or not.

Some adapter (SQLite3) need to perform renaming operations to support
the rails DDL. These rename prefixes operate with prefixes. When an
index name already uses up the full space provieded by
`index_name_length` these internal operations will fail. This patch
introduces `allowed_index_name_length` which respects the amount of
characters used for internal operations. It will always be <=
`index_name_length` and every adapter can define how many characters
need to be reserved.

for query methods in a where_clause. Also, modified the CHANGELOG entry
because it had false information and added tests.

Reduced memory leak problem in transactions by lazily updating AR objects with new transaction state. If AR object has a callback, the callback will be performed immediately (non-lazily) so the transaction still has to keep records with callbacks.