[Active Record] Renamed private methods create_record and update_record

 This is to ensure that they are not accidentally called by the app code.
 They are renamed to _create_record and _update_record respectively.
 Closes #11645
Make AS::SafeBuffer#prepend act like String#prepend

Make `#prepend` method modify instance in-place and return self
instead of just returning modified value. That is exactly what
`#prepend!` method was doing previously, so it's deprecated from
now on.
PostgreSQL determine `Column#type` through corresponding OID. #7814

I ran the whole test suite and compared the old to the new types.
Following is the list of types that did change with this patch:

```
DIFFERENT TYPE FOR mood: NEW: enum, BEFORE:
DIFFERENT TYPE FOR floatrange: NEW: floatrange, BEFORE: float
```

The `floatrange` is a custom type. The old type `float` was simply a coincidence
form the name `floatrange` and our type-guessing.
Merge pull request #14513 from senny/pg/responsible_oid

PostgreSQL determine `Column#type` through corresponding OID. #7814
PostgreSQL, register custom domains. Closes #14305.

This patch registers custom domains in our OID-type_map.
They will behave exactly as the type specified by `pg_type.typbasetype`.

/cc @matthewd
refactor, use `typtype` instead of `typinput` to segment PG types.
fix, adjust OID query without range support to include required fields.

This is a follow-up fix to f7a6b115fea9f675190a79b701c7034214678f19 and
06082f66d541e581110406bbac3bc395bace3f86
Clarify 'database does not exist' message and implementation.

* Clarify what the situation is and what to do.
* Advise loading schema using `rake db:setup` instead of migrating.
* Use a rescue in the initializer rather than extending the error
  message in-place.
* Preserve the original backtrace of other errors by using `raise`
  rather than raising again with `raise error`.

References 0ec45cd15d0a2f5aebc75e23d841b6c12f3ba763
only ask if `t` is empty once.
do not create memo objects since we'll just throw them away
combine move_regexp and move_string so we only loop over states once
push move_string in to `move`
Merge branch 'rmc'

* rmc:
  push move_string in to `move`
  combine move_regexp and move_string so we only loop over states once
  do not create memo objects since we'll just throw them away
  only ask if `t` is empty once.
Changed 'so' to 'see'
Allow postgresql enum_test to be run in random order.

Creating and dropping similar tables within the same connection causes postgresql to look up old values in the cache of tables which have already been dropped.
Merge pull request #14560 from abwinkler999/typo-in-RELEASING_RAILS

Changed 'so' to 'see'
Merge pull request #14550 from tgxworld/fix_failing_enum_test_random_order

Allow postgresql enum_test to be run in random order.
cleanup, `reset_pg_session` in range_test.rb

Also do not use transactional fixtures. We drop the type and the
table after every run, so there is nothing for the transaction to clean up.
PostgreSQL, Support for materialized views. [Dave Lee & Yves Senn]

Expand the query used in #table_exists? to include materialized views in the
kinds of relations it searches.
We can conditional define the tests depending on the adapter or
connection.