this must have been an oversight.   Leave mysql.JSON in place still
as we might need to add things to it.
- CAST(json, String) still confusing MySQL drivers even mysqlclient.
Since here we're checking for the raw form of the JSON and not a typical
round trip, add a force for unicode

Change-Id: I727f4526a01a0875037cf0dede45cd074da5205a

This modifies the Oracle ROWNUM limit/offset approach
to accommodate for the "OF" clause in a "FOR UPDATE"
phrase.  The column expressions must be added to the selected
subquery if necessary and adapted on the outside.

Change-Id: Ia71b5fc4df6d326e73863f8ae9f96e8f1a5acfc1
Fixes: #3741

Some of the dialect impl memoization for TypeDecorator
necessarily keeps the top-level TypeDecorator type
around, since a user-defined type will have bind and result
set processing behavior.  For both TypeDecorator and Variant,
PG dialect needs to ensure it's looking at the SQLAlchemy
type to check for SmallInteger / BigInteger.

Fixes: 3739
Change-Id: I2d45fb997f17c6272d6bb826a77d2dba665adae7
(cherry picked from commit 421fa6b8bf9f0c3c5041579c89ec405ce0f5e0b0)

Rolled back the validation rules a bit in :class:`.Enum` to allow
unknown string values to pass through, unless the flag
``validate_string=True`` is passed to the Enum; any other kind of object is
still of course rejected.  While the immediate use
is to allow comparisons to enums with LIKE, the fact that this
use exists indicates there may be more unknown-string-comparsion use
cases than we expected, which hints that perhaps there are some
unknown string-INSERT cases too.

Change-Id: I7d1d79b374a7d47966d410998f77cd19294ab7b0
Fixes: #3725

Fixes: #3529
Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Change-Id: Ie3bf6ad70d9be9f0e44938830e922db03573991a
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/258

Also adds version detection so that DROP INDEX CONCURRENTLY
only renders if the Postgresql version is 9.2 or higher;
for CREATE INDEX CONCURRENTLY, version detection is added
to allow the phrase to omit if the Postgresql version is
less than 8.2.

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Change-Id: I597287e0ebbbe256c957a3579b58ace6848ab4f4
Pull-request: https://bitbucket.org/zzzeek/sqlalchemy/pull-requests/84

Adds ``key_share=True`` for with_for_update().

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Change-Id: I74e0c3fcbc023e1dc98a1fa0c7db67b4c3693a31
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/279

Fixes: #3588
Change-Id: Ifbfcab67375f289ddb5c4522f4b803cb8b7c34de
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/250