<reponame>ContextLogic/sqlalchemy
"""Global database feature support policy.

Provides decorators to mark tests requiring specific feature support from the
target database.

"""

from testing import \
     _block_unconditionally as no_support, \
     _chain_decorators_on, \
     exclude, \
     emits_warning_on,\
     skip_if,\
     only_on,\
     fails_on,\
     fails_on_everything_except,\
     fails_if
from sqlalchemy import util
from test.lib import config
import testing
import sys

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 foreign_keys(fn):
    """Target database must support foreign keys."""
    return _chain_decorators_on(
        fn,
        no_support('sqlite', 'not supported by database'),
        )


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 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'),
        no_support('sybase', 'not supported by database'),
        no_support('maxdb', 'FIXME: verify not supported by database'),
        no_support('informix', 'not supported by database'),
    )

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 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 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', 'Independent connections disabled when '
                            ':memory: connections are used'),
        exclude('mssql', '<', (9, 0, 0),
                'SQL Server 2005+ is required for independent connections'),
        )

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 isolation_level(fn):
    return _chain_decorators_on(
        fn,
        only_on(('postgresql', 'sqlite'), "DBAPI has no isolation level support"),
        fails_on('postgresql+pypostgresql',
                      'pypostgresql bombs on multiple isolation level calls')
    )

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 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 update_from(fn):
    """Target must support UPDATE..FROM syntax"""
    return _chain_decorators_on(
        fn,
        only_on(('postgresql', 'mssql', 'mysql'), 
            "Backend does not support UPDATE..FROM")
    )

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 denormalized_names(fn):
    """Target database must have 'denormalized', i.e. UPPERCASE as case insensitive names."""

    return skip_if(
                lambda: not testing.db.dialect.requires_name_normalize,
                "Backend does not require denomralized names."
            )(fn)

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 sequences(fn):
    """Target database must support SEQUENCEs."""
    return _chain_decorators_on(
        fn,
        no_support('access', 'no SEQUENCE support'),
        no_support('drizzle', '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'),
        no_support('informix', 'no SEQUENCE support'),
        )

def update_nowait(fn):
    """Target database must support SELECT...FOR UPDATE NOWAIT"""
    return _chain_decorators_on(
        fn,
        no_support('access', 'no FOR UPDATE NOWAIT support'),
        no_support('firebird', 'no FOR UPDATE NOWAIT support'),
        no_support('mssql', 'no FOR UPDATE NOWAIT support'),
        no_support('mysql', 'no FOR UPDATE NOWAIT support'),
        no_support('sqlite', 'no FOR UPDATE NOWAIT support'),
        no_support('sybase', 'no FOR UPDATE NOWAIT support'),
    )

def subqueries(fn):
    """Target database must support subqueries."""
    return _chain_decorators_on(
        fn,
        exclude('mysql', '<', (4, 1, 1), 'no subquery support'),
        )

def intersect(fn):
    """Target database must support INTERSECT or equivlaent."""
    return _chain_decorators_on(
        fn,
        fails_on('firebird', 'no support for INTERSECT'),
        fails_on('mysql', 'no support for INTERSECT'),
        fails_on('sybase', 'no support for INTERSECT'),
        fails_on('informix', 'no support for INTERSECT'),
    )

def except_(fn):
    """Target database must support EXCEPT or equivlaent (i.e. MINUS)."""
    return _chain_decorators_on(
        fn,
        fails_on('firebird', 'no support for EXCEPT'),
        fails_on('mysql', 'no support for EXCEPT'),
        fails_on('sybase', 'no support for EXCEPT'),
        fails_on('informix', 'no support for EXCEPT'),
    )

def offset(fn):
    """Target database must support some method of adding OFFSET or equivalent to a result set."""
    return _chain_decorators_on(
        fn,
        fails_on('sybase', 'no support for OFFSET or equivalent'),
    )

def window_functions(fn):
    return _chain_decorators_on(
        fn,
        only_on(('postgresql', 'mssql', 'oracle'),
                "Backend does not support window functions"),
    )

def returning(fn):
    return _chain_decorators_on(
        fn,
        no_support('access', "'returning' not supported by database"),
        no_support('sqlite', "'returning' not supported by database"),
        no_support('mysql', "'returning' not supported by database"),
        no_support('maxdb', "'returning' not supported by database"),
        no_support('sybase', "'returning' not supported by database"),
        no_support('informix', "'returning' not supported by database"),
    )

def two_phase_transactions(fn):
    """Target database must support two-phase transactions."""
    return _chain_decorators_on(
        fn,
        no_support('access', 'not supported by database'),
        no_support('firebird', 'no SA implementation'),
        no_support('maxdb', 'not supported by database'),
        no_support('mssql', 'FIXME: guessing, needs confirmation'),
        no_support('oracle', 'no SA implementation'),
        no_support('drizzle', 'not supported by database'),
        no_support('sqlite', 'not supported by database'),
        no_support('sybase', 'FIXME: guessing, needs confirmation'),
        no_support('postgresql+zxjdbc', 'FIXME: JDBC driver confuses the transaction state, may '
                   'need separate XA implementation'),
        exclude('mysql', '<', (5, 0, 3), 'not supported by database'),
        )

def views(fn):
    """Target database must support VIEWs."""
    return _chain_decorators_on(
        fn,
        no_support('drizzle', 'no VIEW support'),
        )

def unicode_connections(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,
        exclude('mysql', '<', (4, 1, 1), 'no unicode connection 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'),
        no_support('mssql+pymssql', 'no FreeTDS support'),
        exclude('mysql', '<', (4, 1, 1), 'no unicode connection support'),
        )

def sane_rowcount(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: not testing.db.dialect.supports_sane_rowcount)
    )

def cextensions(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: not _has_cextensions(), "C extensions not installed")
    )

def dbapi_lastrowid(fn):
    if util.pypy:
        return _chain_decorators_on(
            fn,
            fails_if(lambda:True)
        )
    else:
        return _chain_decorators_on(
            fn,
            fails_on_everything_except('mysql+mysqldb', 'mysql+oursql',
                                       'sqlite+pysqlite', 'mysql+pymysql'),
        )

def sane_multi_rowcount(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: not testing.db.dialect.supports_sane_multi_rowcount)
    )

def nullsordering(fn):
    """Target backends that support nulls ordering."""
    return _chain_decorators_on(
        fn,
        fails_on_everything_except('postgresql', 'oracle', 'firebird')
    )

def reflects_pk_names(fn):
    """Target driver reflects the name of primary key constraints."""
    return _chain_decorators_on(
        fn,
        fails_on_everything_except('postgresql', 'oracle')
    )

def python2(fn):
    return _chain_decorators_on(
        fn,
        skip_if(
            lambda: sys.version_info >= (3,),
            "Python version 2.xx is required."
            )
    )

def python3(fn):
    return _chain_decorators_on(
        fn,
        skip_if(
            lambda: sys.version_info < (3,),
            "Python version 3.xx is required."
            )
    )

def python26(fn):
    return _chain_decorators_on(
        fn,
        skip_if(
            lambda: sys.version_info < (2, 6),
            "Python version 2.6 or greater is required"
        )
    )

def python25(fn):
    return _chain_decorators_on(
        fn,
        skip_if(
            lambda: sys.version_info < (2, 5),
            "Python version 2.5 or greater is required"
        )
    )

def cpython(fn):
    return _chain_decorators_on(
         fn,
         skip_if(lambda: util.jython or util.pypy, 
           "cPython interpreter needed"
         )
    )

def _has_cextensions():
    try:
        from sqlalchemy import cresultproxy, cprocessors
        return True
    except ImportError:
        return False

def _has_sqlite():
    from sqlalchemy import create_engine
    try:
        e = create_engine('sqlite://')
        return True
    except ImportError:
        return False

def _has_mysql_on_windows():
    return testing.against('mysql') and \
            testing.db.dialect._server_casing == 1

def _has_mysql_fully_case_sensitive():
    return testing.against('mysql') and \
            testing.db.dialect._server_casing == 0

def sqlite(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: not _has_sqlite())
    )

def ad_hoc_engines(fn):
    """Test environment must allow ad-hoc engine/connection creation.
    
    DBs that scale poorly for many connections, even when closed, i.e.
    Oracle, may use the "--low-connections" option which flags this requirement
    as not present.
    
    """
    return _chain_decorators_on(
        fn,
        skip_if(lambda: config.options.low_connections)
    )

def skip_mysql_on_windows(fn):
    """Catchall for a large variety of MySQL on Windows failures"""

    return _chain_decorators_on(
        fn,
        skip_if(_has_mysql_on_windows,
            "Not supported on MySQL + Windows"
        )
    )

def english_locale_on_postgresql(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: testing.against('postgresql') \
                and not testing.db.scalar('SHOW LC_COLLATE').startswith('en'))
    )

"""Global database feature support policy.

Provides decorators to mark tests requiring specific feature support from the
target database.

"""

from testing import \
     _block_unconditionally as no_support, \
     _chain_decorators_on, \
     exclude, \
     emits_warning_on,\
     skip_if,\
     only_on,\
     fails_on,\
     fails_on_everything_except,\
     fails_if
from sqlalchemy import util
from test.lib import config
import testing
import sys

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 foreign_keys(fn):
    """Target database must support foreign keys."""
    return _chain_decorators_on(
        fn,
        no_support('sqlite', 'not supported by database'),
        )


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 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'),
        no_support('sybase', 'not supported by database'),
        no_support('maxdb', 'FIXME: verify not supported by database'),
        no_support('informix', 'not supported by database'),
    )

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 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 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', 'Independent connections disabled when '
                            ':memory: connections are used'),
        exclude('mssql', '<', (9, 0, 0),
                'SQL Server 2005+ is required for independent connections'),
        )

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 isolation_level(fn):
    return _chain_decorators_on(
        fn,
        only_on(('postgresql', 'sqlite'), "DBAPI has no isolation level support"),
        fails_on('postgresql+pypostgresql',
                      'pypostgresql bombs on multiple isolation level calls')
    )

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 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 update_from(fn):
    """Target must support UPDATE..FROM syntax"""
    return _chain_decorators_on(
        fn,
        only_on(('postgresql', 'mssql', 'mysql'), 
            "Backend does not support UPDATE..FROM")
    )

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 denormalized_names(fn):
    """Target database must have 'denormalized', i.e. UPPERCASE as case insensitive names."""

    return skip_if(
                lambda: not testing.db.dialect.requires_name_normalize,
                "Backend does not require denomralized names."
            )(fn)

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 sequences(fn):
    """Target database must support SEQUENCEs."""
    return _chain_decorators_on(
        fn,
        no_support('access', 'no SEQUENCE support'),
        no_support('drizzle', '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'),
        no_support('informix', 'no SEQUENCE support'),
        )

def update_nowait(fn):
    """Target database must support SELECT...FOR UPDATE NOWAIT"""
    return _chain_decorators_on(
        fn,
        no_support('access', 'no FOR UPDATE NOWAIT support'),
        no_support('firebird', 'no FOR UPDATE NOWAIT support'),
        no_support('mssql', 'no FOR UPDATE NOWAIT support'),
        no_support('mysql', 'no FOR UPDATE NOWAIT support'),
        no_support('sqlite', 'no FOR UPDATE NOWAIT support'),
        no_support('sybase', 'no FOR UPDATE NOWAIT support'),
    )

def subqueries(fn):
    """Target database must support subqueries."""
    return _chain_decorators_on(
        fn,
        exclude('mysql', '<', (4, 1, 1), 'no subquery support'),
        )

def intersect(fn):
    """Target database must support INTERSECT or equivlaent."""
    return _chain_decorators_on(
        fn,
        fails_on('firebird', 'no support for INTERSECT'),
        fails_on('mysql', 'no support for INTERSECT'),
        fails_on('sybase', 'no support for INTERSECT'),
        fails_on('informix', 'no support for INTERSECT'),
    )

def except_(fn):
    """Target database must support EXCEPT or equivlaent (i.e. MINUS)."""
    return _chain_decorators_on(
        fn,
        fails_on('firebird', 'no support for EXCEPT'),
        fails_on('mysql', 'no support for EXCEPT'),
        fails_on('sybase', 'no support for EXCEPT'),
        fails_on('informix', 'no support for EXCEPT'),
    )

def offset(fn):
    """Target database must support some method of adding OFFSET or equivalent to a result set."""
    return _chain_decorators_on(
        fn,
        fails_on('sybase', 'no support for OFFSET or equivalent'),
    )

def window_functions(fn):
    return _chain_decorators_on(
        fn,
        only_on(('postgresql', 'mssql', 'oracle'),
                "Backend does not support window functions"),
    )

def returning(fn):
    return _chain_decorators_on(
        fn,
        no_support('access', "'returning' not supported by database"),
        no_support('sqlite', "'returning' not supported by database"),
        no_support('mysql', "'returning' not supported by database"),
        no_support('maxdb', "'returning' not supported by database"),
        no_support('sybase', "'returning' not supported by database"),
        no_support('informix', "'returning' not supported by database"),
    )

def two_phase_transactions(fn):
    """Target database must support two-phase transactions."""
    return _chain_decorators_on(
        fn,
        no_support('access', 'not supported by database'),
        no_support('firebird', 'no SA implementation'),
        no_support('maxdb', 'not supported by database'),
        no_support('mssql', 'FIXME: guessing, needs confirmation'),
        no_support('oracle', 'no SA implementation'),
        no_support('drizzle', 'not supported by database'),
        no_support('sqlite', 'not supported by database'),
        no_support('sybase', 'FIXME: guessing, needs confirmation'),
        no_support('postgresql+zxjdbc', 'FIXME: JDBC driver confuses the transaction state, may '
                   'need separate XA implementation'),
        exclude('mysql', '<', (5, 0, 3), 'not supported by database'),
        )

def views(fn):
    """Target database must support VIEWs."""
    return _chain_decorators_on(
        fn,
        no_support('drizzle', 'no VIEW support'),
        )

def unicode_connections(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,
        exclude('mysql', '<', (4, 1, 1), 'no unicode connection 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'),
        no_support('mssql+pymssql', 'no FreeTDS support'),
        exclude('mysql', '<', (4, 1, 1), 'no unicode connection support'),
        )

def sane_rowcount(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: not testing.db.dialect.supports_sane_rowcount)
    )

def cextensions(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: not _has_cextensions(), "C extensions not installed")
    )

def dbapi_lastrowid(fn):
    if util.pypy:
        return _chain_decorators_on(
            fn,
            fails_if(lambda:True)
        )
    else:
        return _chain_decorators_on(
            fn,
            fails_on_everything_except('mysql+mysqldb', 'mysql+oursql',
                                       'sqlite+pysqlite', 'mysql+pymysql'),
        )

def sane_multi_rowcount(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: not testing.db.dialect.supports_sane_multi_rowcount)
    )

def nullsordering(fn):
    """Target backends that support nulls ordering."""
    return _chain_decorators_on(
        fn,
        fails_on_everything_except('postgresql', 'oracle', 'firebird')
    )

def reflects_pk_names(fn):
    """Target driver reflects the name of primary key constraints."""
    return _chain_decorators_on(
        fn,
        fails_on_everything_except('postgresql', 'oracle')
    )

def python2(fn):
    return _chain_decorators_on(
        fn,
        skip_if(
            lambda: sys.version_info >= (3,),
            "Python version 2.xx is required."
            )
    )

def python3(fn):
    return _chain_decorators_on(
        fn,
        skip_if(
            lambda: sys.version_info < (3,),
            "Python version 3.xx is required."
            )
    )

def python26(fn):
    return _chain_decorators_on(
        fn,
        skip_if(
            lambda: sys.version_info < (2, 6),
            "Python version 2.6 or greater is required"
        )
    )

def python25(fn):
    return _chain_decorators_on(
        fn,
        skip_if(
            lambda: sys.version_info < (2, 5),
            "Python version 2.5 or greater is required"
        )
    )

def cpython(fn):
    return _chain_decorators_on(
         fn,
         skip_if(lambda: util.jython or util.pypy, 
           "cPython interpreter needed"
         )
    )

def _has_cextensions():
    try:
        from sqlalchemy import cresultproxy, cprocessors
        return True
    except ImportError:
        return False

def _has_sqlite():
    from sqlalchemy import create_engine
    try:
        e = create_engine('sqlite://')
        return True
    except ImportError:
        return False

def _has_mysql_on_windows():
    return testing.against('mysql') and \
            testing.db.dialect._server_casing == 1

def _has_mysql_fully_case_sensitive():
    return testing.against('mysql') and \
            testing.db.dialect._server_casing == 0

def sqlite(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: not _has_sqlite())
    )

def ad_hoc_engines(fn):
    """Test environment must allow ad-hoc engine/connection creation.
    
    DBs that scale poorly for many connections, even when closed, i.e.
    Oracle, may use the "--low-connections" option which flags this requirement
    as not present.
    
    """
    return _chain_decorators_on(
        fn,
        skip_if(lambda: config.options.low_connections)
    )

def skip_mysql_on_windows(fn):
    """Catchall for a large variety of MySQL on Windows failures"""

    return _chain_decorators_on(
        fn,
        skip_if(_has_mysql_on_windows,
            "Not supported on MySQL + Windows"
        )
    )

def english_locale_on_postgresql(fn):
    return _chain_decorators_on(
        fn,
        skip_if(lambda: testing.against('postgresql') \
                and not testing.db.scalar('SHOW LC_COLLATE').startswith('en'))
    )
Global database feature support policy.  Provides decorators to mark tests requiring specific feature support from the target database. Target database must support derferable constraints. Target database must support foreign keys. Target database must support VARCHAR with no length Target database must support boolean expressions as columns 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. Target must support simultaneous, independent database cursors on a single connection. Target must support simultaneous, independent database connections. # This is also true of some configurations of UnixODBC and probably win32 # ODBC as well. Target must support UPDATE on autoincrement/integer primary key. Target must support standard statement-running EACH ROW triggers. # no access to same table # huh?  TODO: implement triggers for PG tests, remove this Target must support an outer join to a subquery which correlates to the parent. Target must support UPDATE..FROM syntax Target database must support savepoints. Target database must have 'denormalized', i.e. UPPERCASE as case insensitive names. Target database must support external schemas, and have one named 'test_schema'. Target database must support SEQUENCEs. Target database must support SELECT...FOR UPDATE NOWAIT Target database must support subqueries. Target database must support INTERSECT or equivlaent. Target database must support EXCEPT or equivlaent (i.e. MINUS). Target database must support some method of adding OFFSET or equivalent to a result set. Target database must support two-phase transactions. Target database must support VIEWs. Target driver must support some encoding of Unicode across the wire. # TODO: expand to exclude MySQLdb versions w/ broken unicode Target driver must support some encoding of Unicode across the wire. # TODO: expand to exclude MySQLdb versions w/ broken unicode Target backends that support nulls ordering. Target driver reflects the name of primary key constraints. Test environment must allow ad-hoc engine/connection creation.          DBs that scale poorly for many connections, even when closed, i.e.     Oracle, may use the "--low-connections" option which flags this requirement     as not present. Catchall for a large variety of MySQL on Windows failures