def updateable_autoincrement_pks(fn):
    """Target must support UPDATE on autoincrement/integer primary key."""
    return _chain_decorators_on(
        fn,
        no_support('mssql', "IDENTITY cols can't be updated"),
        no_support('sybase', "IDENTITY cols can't be updated"),
    )

def independent_cursors(fn):
    """Target must support simultaneous, independent database cursors on a single connection."""

    return _chain_decorators_on(
        fn,
        no_support('mssql+pyodbc', 'no driver support'),
        no_support('mssql+mxodbc', 'no driver support'),
        )

def unbounded_varchar(fn):
    """Target database must support VARCHAR with no length"""
    return _chain_decorators_on(
        fn,
        no_support('firebird', 'not supported by database'),
        no_support('oracle', 'not supported by database'),
        no_support('mysql', 'not supported by database'),
    )

def deferrable_constraints(fn):
    """Target database must support derferable constraints."""
    return _chain_decorators_on(
        fn,
        no_support('firebird', 'not supported by database'),
        no_support('mysql', 'not supported by database'),
        no_support('mssql', 'not supported by database'),
        )

def boolean_col_expressions(fn):
    """Target database must support boolean expressions as columns"""
    return _chain_decorators_on(
        fn,
        no_support('firebird', 'not supported by database'),
        no_support('oracle', 'not supported by database'),
        no_support('mssql', 'not supported by database'),
    )

def schemas(fn):
    """Target database must support external schemas, and have one named 'test_schema'."""

    return _chain_decorators_on(
        fn,
        no_support('sqlite', 'no schema support'),
        no_support('firebird', 'no schema support')
    )

def deferrable_constraints(fn):
    """Target database must support derferable constraints."""
    return _chain_decorators_on(
        fn,
        no_support("firebird", "not supported by database"),
        no_support("mysql", "not supported by database"),
        no_support("mssql", "not supported by database"),
    )

def row_triggers(fn):
    """Target must support standard statement-running EACH ROW triggers."""
    return _chain_decorators_on(
        fn,
        # no access to same table
        no_support('mysql', 'requires SUPER priv'),
        exclude('mysql', '<', (5, 0, 10), 'not supported by database'),
        no_support('postgres', 'not supported by database: no statements'),
        )

def sequences(fn):
    """Target database must support SEQUENCEs."""
    return _chain_decorators_on(
        fn,
        no_support('access', 'no SEQUENCE support'),
        no_support('mssql', 'no SEQUENCE support'),
        no_support('mysql', 'no SEQUENCE support'),
        no_support('sqlite', 'no SEQUENCE support'),
        no_support('sybase', 'no SEQUENCE support'),
        )

def sequences(fn):
    """Target database must support SEQUENCEs."""
    return _chain_decorators_on(
        fn,
        no_support("access", "no SEQUENCE support"),
        no_support("mssql", "no SEQUENCE support"),
        no_support("mysql", "no SEQUENCE support"),
        no_support("sqlite", "no SEQUENCE support"),
        no_support("sybase", "no SEQUENCE support"),
    )

def unicode_ddl(fn):
    """Target driver must support some encoding of Unicode across the wire."""
    # TODO: expand to exclude MySQLdb versions w/ broken unicode
    return _chain_decorators_on(
        fn,
        no_support('maxdb', 'database support flakey'),
        no_support('oracle', 'FIXME: no support in database?'),
        no_support('sybase', 'FIXME: guessing, needs confirmation'),
        exclude('mysql', '<', (4, 1, 1), 'no unicode connection support'),
        )

def savepoints(fn):
    """Target database must support savepoints."""
    return _chain_decorators_on(
        fn,
        emits_warning_on("mssql", "Savepoint support in mssql is experimental and may lead to data loss."),
        no_support("access", "not supported by database"),
        no_support("sqlite", "not supported by database"),
        no_support("sybase", "FIXME: guessing, needs confirmation"),
        exclude("mysql", "<", (5, 0, 3), "not supported by database"),
    )

def row_triggers(fn):
    """Target must support standard statement-running EACH ROW triggers."""
    return _chain_decorators_on(
        fn,
        # no access to same table
        no_support("mysql", "requires SUPER priv"),
        exclude("mysql", "<", (5, 0, 10), "not supported by database"),
        # huh?  TODO: implement triggers for PG tests, remove this
        no_support("postgresql", "PG triggers need to be implemented for tests"),
    )

def savepoints(fn):
    """Target database must support savepoints."""
    return _chain_decorators_on(
        fn,
        no_support('access', 'savepoints not supported'),
        no_support('sqlite', 'savepoints not supported'),
        no_support('sybase', 'savepoints not supported'),
        exclude('mysql', '<', (5, 0, 3), 'savepoints not supported'),
        exclude('informix', '<', (11, 55, 'xC3'), 'savepoints not supported'),
        )

def unicode_ddl(fn):
    """Target driver must support some encoding of Unicode across the wire."""
    # TODO: expand to exclude MySQLdb versions w/ broken unicode
    return _chain_decorators_on(
        fn,
        no_support("maxdb", "database support flakey"),
        no_support("oracle", "FIXME: no support in database?"),
        no_support("sybase", "FIXME: guessing, needs confirmation"),
        exclude("mysql", "<", (4, 1, 1), "no unicode connection support"),
    )

def savepoints(fn):
    """Target database must support savepoints."""
    return _chain_decorators_on(
        fn,
        emits_warning_on('mssql', 'Savepoint support in mssql is experimental and may lead to data loss.'),
        no_support('access', 'not supported by database'),
        no_support('sqlite', 'not supported by database'),
        no_support('sybase', 'FIXME: guessing, needs confirmation'),
        exclude('mysql', '<', (5, 0, 3), 'not supported by database'),
        )

def savepoints(fn):
    """Target database must support savepoints."""
    return _chain_decorators_on(
        fn,
        emits_warning_on('mssql', 'Savepoint support in mssql is experimental and may lead to data loss.'),
        no_support('access', 'savepoints not supported'),
        no_support('sqlite', 'savepoints not supported'),
        no_support('sybase', 'savepoints not supported'),
        exclude('mysql', '<', (5, 0, 3), 'savepoints not supported'),
        exclude('informix', '<', (11, 55, 'xC3'), 'savepoints not supported'),
        )

def identity(fn):
    """Target database must support GENERATED AS IDENTITY or a facsimile.

    Includes GENERATED AS IDENTITY, AUTOINCREMENT, AUTO_INCREMENT, or other
    column DDL feature that fills in a DB-generated identifier at INSERT-time
    without requiring pre-execution of a SEQUENCE or other artifact.

    """
    return _chain_decorators_on(
        fn,
        no_support('firebird', 'not supported by database'),
        no_support('oracle', 'not supported by database'),
        no_support('postgresql', 'not supported by database'),
        no_support('sybase', 'not supported by database'),
        )

def correlated_outer_joins(fn):
    """Target must support an outer join to a subquery which correlates to the parent."""

    return _chain_decorators_on(
        fn,
        no_support('oracle', 'Raises "ORA-01799: a column may not be outer-joined to a subquery"')
    )

def independent_connections(fn):
    """Target must support simultaneous, independent database connections."""

    # This is also true of some configurations of UnixODBC and probably win32
    # ODBC as well.
    return _chain_decorators_on(
        fn,
        no_support('sqlite', 'no driver support')
        )