Added new keywords :paramref:`.Sequence.cache` and
:paramref:`.Sequence.order` to :class:`.Sequence`, to allow rendering
of the CACHE parameter understood by Oracle and PostgreSQL, and the
ORDER parameter understood by Oracle.  Pull request
courtesy David Moore.

Change-Id: I082c3f8ef56ef89dbaad5da9d5695be5313b0614
Pull-request: https://bitbucket.org/zzzeek/sqlalchemy/pull-requests/96

Added a new kind of :func:`.bindparam` called "expanding".  This is
for use in ``IN`` expressions where the list of elements is rendered
into individual bound parameters at statement execution time, rather
than at statement compilation time.  This allows both a single bound
parameter name to be linked to an IN expression of multiple elements,
as well as allows query caching to be used with IN expressions.  The
new feature allows the related features of "select in" loading and
"polymorphic in" loading to make use of the baked query extension
to reduce call overhead.   This feature should be considered to be
**experimental** for 1.2.

Fixes: #3953
Change-Id: Ie708414a3ab9c0af29998a2c7f239ff7633b1f6e

This patch moves the "doubling" of percent signs into
the base compiler and makes it completely a product
of whether or not the paramstyle is format/pyformat or
not.   Without this paramstyle, percent signs
are not doubled across text(), literal_column(), and
column().

Change-Id: Ie2f278ab1dbb94b5078f85c0096d74dbfa049197
Fixes: #3740

Fixed bug where a column-level :class:`.CheckConstraint` would fail
to compile the SQL expression using the underlying dialect compiler
as well as apply proper flags to generate literal values as
inline, in the case that the sqltext is a Core expression and
not just a plain string.   This was long-ago fixed for table-level
check constraints in 0.9 as part of :ticket:`2742`, which more commonly
feature Core SQL expressions as opposed to plain string expressions.

Change-Id: I1301ba4b40063e91bc47726aecc5f4990ffcaeda
Fixes: #3957

After bump minimum supported version to 2.7 (1da9d3752160430c91534a8868ceb8c5ad1451d4), we can use new syntax.

Change-Id: Ib064c75a00562e641d132f9c57e5e69744200e05
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/347

Added support for SQL comments on :class:`.Table` and :class:`.Column`
objects, via the new :paramref:`.Table.comment` and
:paramref:`.Column.comment` arguments.   The comments are included
as part of DDL on table creation, either inline or via an appropriate
ALTER statement, and are also reflected back within table reflection,
as well as via the :class:`.Inspector`.   Supported backends currently
include MySQL, Postgresql, and Oracle.

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Fixes: #1546
Change-Id: Ib90683850805a2b4ee198e420dc294f32f15d35d

The longstanding behavior of the :meth:`.Operators.in_` and
:meth:`.Operators.not_in_` operators emitting a warning when
the right-hand condition is an empty sequence has been revised;
a new flag :paramref:`.create_engine.empty_in_strategy` allows an
empty "IN" expression to generate a simple boolean expression, or
to invoke the previous behavior of dis-equating the expression to
itself, with or without a warning.  The default behavior is now
to emit the simple boolean expression, allowing an empty IN to
be evaulated without any performance penalty.

Change-Id: I65cc37f2d7cf65a59bf217136c42fee446929352
Fixes: #3907

Fixed bug in compiler where the string identifier of a savepoint would
be cached in the identifier quoting dictionary; as these identifiers
are arbitrary, a small memory leak could occur if a single
:class:`.Connection` had an unbounded number of savepoints used,
as well as if the savepoint clause constructs were used directly
with an unbounded umber of savepoint names.   The memory leak does
**not** impact the vast majority of cases as normally the
:class:`.Connection`, which renders savepoint names with a simple
counter starting at "1", is used on a per-transaction or
per-fixed-number-of-transactions basis before being discarded.

The savepoint name in virtually all cases does not require quoting
at all, however to support potential third party use cases
the "check for quotes needed" logic is retained, at a small
performance cost.   Uncondtionally quoting the name is another
option, but this would turn the name into a case sensitive name
which runs the risk of poor interactions with existing deployments
that may be looking at these names in other contexts.

Change-Id: I6b53c96abf7fdf1840592bbca5da81347911844c
Fixes: #3931

Corrects some warnings and adds tox config.  Adds DeprecationWarning
to the error category.   Large sweep for string literals w/ backslashes
as this is common in docstrings

Co-authored-by: Andrii Soldatenko
Fixes: #3886
Change-Id: Ia7c838dfbbe70b262622ed0803d581edc736e085
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/337