# Source code for sqlobject.col

    """
    Col -- SQLObject columns

    Note that each column object is named BlahBlahCol, and these are used
    in class definitions.  But there's also a corresponding SOBlahBlahCol
    object, which is used in SQLObject *classes*.

    An explanation: when a SQLObject subclass is created, the metaclass
    looks through your class definition for any subclasses of Col.  It
    collects them together, and indexes them to do all the database stuff
    you like, like the magic attributes and whatnot.  It then asks the Col
    object to create an SOCol object (usually a subclass, actually).  The
    SOCol object contains all the interesting logic, as well as a record
    of the attribute name you used and the class it is bound to (set by
    the metaclass).

    So, in summary: Col objects are what you define, but SOCol objects
    are what gets used.
    """

    from array import array
    from decimal import Decimal
    from itertools import count
    import json
    try:
        import cPickle as pickle
    except ImportError:
        import pickle
    import time
    from uuid import UUID
    import weakref

    from formencode import compound, validators
    from .classregistry import findClass
    # Sadly the name "constraints" conflicts with many of the function
    # arguments in this module, so we rename it:
    from . import constraints as constrs
    from . import converters
    from . import sqlbuilder
    from .styles import capword
    from .compat import PY2, string_type, unicode_type, buffer_type

    import datetime
    datetime_available = True

    try:
        from mx import DateTime as mxDateTime
    except ImportError:
        mxdatetime_available = False
    else:
        mxdatetime_available = True

    try:
        # DateTime from Zope
        import DateTime as zopeDateTime
    except ImportError:
        zope_datetime_available = False
    else:
        zope_datetime_available = True

    DATETIME_IMPLEMENTATION = "datetime"
    MXDATETIME_IMPLEMENTATION = "mxDateTime"
    ZOPE_DATETIME_IMPLEMENTATION = "zopeDateTime"

    if mxdatetime_available and hasattr(mxDateTime, "Time"):
        mxDateTimeType = type(mxDateTime.now())
        mxTimeType = type(mxDateTime.Time())

    if zope_datetime_available:
        zopeDateTimeType = type(zopeDateTime.DateTime())

    __all__ = ["datetime_available", "mxdatetime_available",
               "default_datetime_implementation", "DATETIME_IMPLEMENTATION"]

    if mxdatetime_available:
        __all__.append("MXDATETIME_IMPLEMENTATION")

    if zope_datetime_available:
        __all__.append("ZOPE_DATETIME_IMPLEMENTATION")

    default_datetime_implementation = DATETIME_IMPLEMENTATION

    if not PY2:
        # alias for python 3 compatibility
        long = int
        # This is to satisfy flake8 under python 3
        unicode = str

    NoDefault = sqlbuilder.NoDefault

    def use_microseconds(use=True):
        if use:
            SODateTimeCol.datetimeFormat = '%Y-%m-%d %H:%M:%S.%f'
            SOTimeCol.timeFormat = '%H:%M:%S.%f'
            dt_types = [(datetime.datetime, converters.DateTimeConverterMS),
                        (datetime.time, converters.TimeConverterMS)]
        else:
            SODateTimeCol.datetimeFormat = '%Y-%m-%d %H:%M:%S'
            SOTimeCol.timeFormat = '%H:%M:%S'
            dt_types = [(datetime.datetime, converters.DateTimeConverter),
                        (datetime.time, converters.TimeConverter)]
        for dt_type, converter in dt_types:
            converters.registerConverter(dt_type, converter)

    __all__.append("use_microseconds")

    creationOrder = count()

    ########################################
    # Columns
    ########################################

    # Col is essentially a column definition, it doesn't have much logic to it.

    class SOCol(object):

        def __init__(self,
                     name,
                     soClass,
                     creationOrder,
                     dbName=None,
                     default=NoDefault,
                     defaultSQL=None,
                     foreignKey=None,
                     alternateID=False,
                     alternateMethodName=None,
                     constraints=None,
                     notNull=NoDefault,
                     notNone=NoDefault,
                     unique=NoDefault,
                     sqlType=None,
                     columnDef=None,
                     validator=None,
                     validator2=None,
                     immutable=False,
                     cascade=None,
                     lazy=False,
                     noCache=False,
                     forceDBName=False,
                     title=None,
                     tags=[],
                     origName=None,
                     dbEncoding=None,
                     extra_vars=None):

            super(SOCol, self).__init__()

            # This isn't strictly true, since we *could* use backquotes or
            # " or something (database-specific) around column names, but
            # why would anyone *want* to use a name like that?
            # @@: I suppose we could actually add backquotes to the
            # dbName if we needed to...
            if not forceDBName:
                assert sqlbuilder.sqlIdentifier(name), (
                    'Name must be SQL-safe '
                    '(letters, numbers, underscores): %s (or use forceDBName=True)'
                    % repr(name))
            assert name != 'id', (
                'The column name "id" is reserved for SQLObject use '
                '(and is implicitly created).')
            assert name, "You must provide a name for all columns"

            self.columnDef = columnDef
            self.creationOrder = creationOrder

            self.immutable = immutable

            # cascade can be one of:
            # None: no constraint is generated
            # True: a CASCADE constraint is generated
            # False: a RESTRICT constraint is generated
            # 'null': a SET NULL trigger is generated
            if not isinstance(cascade, (bool, string_type, type(None))):
                raise TypeError(
                    'Expected cascade to be True, False, None or "null", '
                    "(you gave: %r %r)" % (type(cascade), cascade)
                )
            if isinstance(cascade, str) and (cascade != 'null'):
                raise ValueError(
                    "The only string value allowed for cascade is 'null' "
                    "(you gave: %r)" % cascade)
            self.cascade = cascade

            if not isinstance(constraints, (list, tuple)):
                constraints = [constraints]
            self.constraints = self.autoConstraints() + constraints

            self.notNone = False
            if notNull is not NoDefault:
                self.notNone = notNull
                assert notNone is NoDefault or (not notNone) == (not notNull), (
                    "The notNull and notNone arguments are aliases, "
                    "and must not conflict.  "
                    "You gave notNull=%r, notNone=%r" % (notNull, notNone))
            elif notNone is not NoDefault:
                self.notNone = notNone
            if self.notNone:
                self.constraints = [constrs.notNull] + self.constraints

            self.name = name
            self.soClass = soClass
            self._default = default
            self.defaultSQL = defaultSQL
            self.customSQLType = sqlType

            # deal with foreign keys
            self.foreignKey = foreignKey
            if self.foreignKey:
                if origName is not None:
                    idname = soClass.sqlmeta.style.instanceAttrToIDAttr(origName)
                else:
                    idname = soClass.sqlmeta.style.instanceAttrToIDAttr(name)
                if self.name != idname:
                    self.foreignName = self.name
                    self.name = idname
                else:
                    self.foreignName = soClass.sqlmeta.style.\
                        instanceIDAttrToAttr(self.name)
            else:
                self.foreignName = None

            # if they don't give us a specific database name for
            # the column, we separate the mixedCase into mixed_case
            # and assume that.
            if dbName is None:
                self.dbName = soClass.sqlmeta.style.pythonAttrToDBColumn(self.name)
            else:
                self.dbName = dbName

            # alternateID means that this is a unique column that
            # can be used to identify rows
            self.alternateID = alternateID

            if unique is NoDefault:
                self.unique = alternateID
            else:
                self.unique = unique
            if self.unique and alternateMethodName is None:
                self.alternateMethodName = 'by' + capword(self.name)
            else:
                self.alternateMethodName = alternateMethodName

            _validators = self.createValidators()
            if validator:
                _validators.append(validator)
            if validator2:
                _validators.insert(0, validator2)
            _vlen = len(_validators)
            if _vlen:
                for _validator in _validators:
                    _validator.soCol = weakref.proxy(self)
            if _vlen == 0:
                self.validator = None  # Set sef.{from,to}_python
            elif _vlen == 1:
                self.validator = _validators[0]
            elif _vlen > 1:
                self.validator = compound.All.join(
                    _validators[0], *_validators[1:])
            self.noCache = noCache
            self.lazy = lazy
            # this is in case of ForeignKey, where we rename the column
            # and append an ID
            self.origName = origName or name
            self.title = title
            self.tags = tags
            self.dbEncoding = dbEncoding

            if extra_vars:
                for name, value in extra_vars.items():
                    setattr(self, name, value)

        def _set_validator(self, value):
            self._validator = value
            if self._validator:
                self.to_python = self._validator.to_python
                self.from_python = self._validator.from_python
            else:
                self.to_python = None
                self.from_python = None

        def _get_validator(self):
            return self._validator

        validator = property(_get_validator, _set_validator)

        def createValidators(self):
            """Create a list of validators for the column."""
            return []

        def autoConstraints(self):
            return []

        def _get_default(self):
            # A default can be a callback or a plain value,
            # here we resolve the callback
            if self._default is NoDefault:
                return NoDefault
            elif hasattr(self._default, '__sqlrepr__'):
                return self._default
            elif callable(self._default):
                return self._default()
            else:
                return self._default
        default = property(_get_default, None, None)

        def _get_joinName(self):
            return self.soClass.sqlmeta.style.instanceIDAttrToAttr(self.name)
        joinName = property(_get_joinName, None, None)

        def __repr__(self):
            r = '<%s %s' % (self.__class__.__name__, self.name)
            if self.default is not NoDefault:
                r += ' default=%s' % repr(self.default)
            if self.foreignKey:
                r += ' connected to %s' % self.foreignKey
            if self.alternateID:
                r += ' alternate ID'
            if self.notNone:
                r += ' not null'
            return r + '>'

        def createSQL(self):
            return ' '.join([self._sqlType()] + self._extraSQL())

        def _extraSQL(self):
            result = []
            if self.notNone or self.alternateID:
                result.append('NOT NULL')
            if self.unique or self.alternateID:
                result.append('UNIQUE')
            if self.defaultSQL is not None:
                result.append("DEFAULT %s" % self.defaultSQL)
            return result

        def _sqlType(self):
            if self.customSQLType is None:
                raise ValueError("Col %s (%s) cannot be used for automatic "
                                 "schema creation (too abstract)" %
                                 (self.name, self.__class__))
            else:
                return self.customSQLType

        def _mysqlType(self):
            return self._sqlType()

        def _postgresType(self):
            return self._sqlType()

        def _sqliteType(self):
            # SQLite is naturally typeless, so as a fallback it uses
            # no type.
            try:
                return self._sqlType()
            except ValueError:
                return ''

        def _sybaseType(self):
            return self._sqlType()

        def _mssqlType(self):
            return self._sqlType()

        def _firebirdType(self):
            return self._sqlType()

        def _maxdbType(self):
            return self._sqlType()

        def mysqlCreateSQL(self, connection=None):
            self.connection = connection
            return ' '.join([self.dbName, self._mysqlType()] + self._extraSQL())

        def postgresCreateSQL(self):
            return ' '.join([self.dbName, self._postgresType()] + self._extraSQL())

        def sqliteCreateSQL(self):
            return ' '.join([self.dbName, self._sqliteType()] + self._extraSQL())

        def sybaseCreateSQL(self):
            return ' '.join([self.dbName, self._sybaseType()] + self._extraSQL())

        def mssqlCreateSQL(self, connection=None):
            self.connection = connection
            return ' '.join([self.dbName, self._mssqlType()] + self._extraSQL())

        def firebirdCreateSQL(self):
            # Ian Sparks pointed out that fb is picky about the order
            # of the NOT NULL clause in a create statement.  So, we handle
            # them differently for Enum columns.
            if not isinstance(self, SOEnumCol):
                return ' '.join(
                    [self.dbName, self._firebirdType()] + self._extraSQL())
            else:
                return ' '.join(
                    [self.dbName] + [self._firebirdType()[0]]
                    + self._extraSQL() + [self._firebirdType()[1]])

        def maxdbCreateSQL(self):
            return ' '.join([self.dbName, self._maxdbType()] + self._extraSQL())

        def __get__(self, obj, type=None):
            if obj is None:
                # class attribute, return the descriptor itself
                return self
            if obj.sqlmeta._obsolete:
                raise RuntimeError('The object <%s %s> is obsolete' % (
                    obj.__class__.__name__, obj.id))
            if obj.sqlmeta.cacheColumns:
                columns = obj.sqlmeta._columnCache
                if columns is None:
                    obj.sqlmeta.loadValues()
                try:
                    return columns[name]  # noqa
                except KeyError:
                    return obj.sqlmeta.loadColumn(self)
            else:
                return obj.sqlmeta.loadColumn(self)

        def __set__(self, obj, value):
            if self.immutable:
                raise AttributeError("The column %s.%s is immutable" %
                                     (obj.__class__.__name__,
                                      self.name))
            obj.sqlmeta.setColumn(self, value)

        def __delete__(self, obj):
            raise AttributeError("I can't be deleted from %r" % obj)

        def getDbEncoding(self, state, default='utf-8'):
            if self.dbEncoding:
                return self.dbEncoding
            dbEncoding = state.soObject.sqlmeta.dbEncoding
            if dbEncoding:
                return dbEncoding
            try:
                connection = state.connection or state.soObject._connection
            except AttributeError:
                dbEncoding = None
            else:
                dbEncoding = getattr(connection, "dbEncoding", None)
            if not dbEncoding:
                dbEncoding = default
            return dbEncoding

    class Col(object):

        baseClass = SOCol

        def __init__(self, name=None, **kw):
            super(Col, self).__init__()
            self.__dict__['_name'] = name
            self.__dict__['_kw'] = kw
            self.__dict__['creationOrder'] = next(creationOrder)
            self.__dict__['_extra_vars'] = {}

        def _set_name(self, value):
            assert self._name is None or self._name == value, (
                "You cannot change a name after it has already been set "
                "(from %s to %s)" % (self.name, value))
            self.__dict__['_name'] = value

        def _get_name(self):
            return self._name

        name = property(_get_name, _set_name)

        def withClass(self, soClass):
            return self.baseClass(soClass=soClass, name=self._name,
                                  creationOrder=self.creationOrder,
                                  columnDef=self,
                                  extra_vars=self._extra_vars,
                                  **self._kw)

        def __setattr__(self, var, value):
            if var == 'name':
                super(Col, self).__setattr__(var, value)
                return
            self._extra_vars[var] = value

        def __repr__(self):
            return '<%s %s %s>' % (
                self.__class__.__name__, hex(abs(id(self)))[2:],
                self._name or '(unnamed)')

    class SOValidator(validators.Validator):
        def getDbEncoding(self, state, default='utf-8'):
            try:
                return self.dbEncoding
            except AttributeError:
                return self.soCol.getDbEncoding(state, default=default)

    class SOStringLikeCol(SOCol):
        """A common ancestor for SOStringCol and SOUnicodeCol"""
        def __init__(self, **kw):
            self.length = kw.pop('length', None)
            self.varchar = kw.pop('varchar', 'auto')
            self.char_binary = kw.pop('char_binary', None)  # A hack for MySQL
            if not self.length:
                assert self.varchar == 'auto' or not self.varchar, \
                    "Without a length strings are treated as TEXT, not varchar"
                self.varchar = False
            elif self.varchar == 'auto':
                self.varchar = True

            super(SOStringLikeCol, self).__init__(**kw)

        def autoConstraints(self):
            constraints = [constrs.isString]
            if self.length is not None:
                constraints += [constrs.MaxLength(self.length)]
            return constraints

        def _sqlType(self):
            if self.customSQLType is not None:
                return self.customSQLType
            if not self.length:
                return 'TEXT'
            elif self.varchar:
                return 'VARCHAR(%i)' % self.length
            else:
                return 'CHAR(%i)' % self.length

        def _check_case_sensitive(self, db):
            if self.char_binary:
                raise ValueError("%s does not support "
                                 "binary character columns" % db)

        def _mysqlType(self):
            type = self._sqlType()
            if self.char_binary:
                type += " BINARY"
            return type

        def _postgresType(self):
            self._check_case_sensitive("PostgreSQL")
            return super(SOStringLikeCol, self)._postgresType()

        def _sqliteType(self):
            self._check_case_sensitive("SQLite")
            return super(SOStringLikeCol, self)._sqliteType()

        def _sybaseType(self):
            self._check_case_sensitive("SYBASE")
            type = self._sqlType()
            return type

        def _mssqlType(self):
            if self.customSQLType is not None:
                return self.customSQLType
            if not self.length:
                if self.connection and self.connection.can_use_max_types():
                    type = 'VARCHAR(MAX)'
                else:
                    type = 'VARCHAR(4000)'
            elif self.varchar:
                type = 'VARCHAR(%i)' % self.length
            else:
                type = 'CHAR(%i)' % self.length
            return type

        def _firebirdType(self):
            self._check_case_sensitive("FireBird")
            if not self.length:
                return 'BLOB SUB_TYPE TEXT'
            else:
                return self._sqlType()

        def _maxdbType(self):
            self._check_case_sensitive("SAP DB/MaxDB")
            if not self.length:
                return 'LONG ASCII'
            else:
                return self._sqlType()

    class StringValidator(SOValidator):

        def to_python(self, value, state):
            if value is None:
                return None
            try:
                connection = state.connection or state.soObject._connection
                binaryType = connection._binaryType
                dbName = connection.dbName
            except AttributeError:
                binaryType = type(None)  # Just a simple workaround
            dbEncoding = self.getDbEncoding(state, default='ascii')
            if isinstance(value, unicode_type):
                if PY2:
                    return value.encode(dbEncoding)
                return value
            if self.dataType and isinstance(value, self.dataType):
                return value
            if isinstance(value,
                          (str, bytes, buffer_type, binaryType,
                           sqlbuilder.SQLExpression)):
                return value
            if hasattr(value, '__unicode__'):
                return unicode(value).encode(dbEncoding)
            if dbName == 'mysql':
                if isinstance(value, bytearray):
                    if PY2:
                        return bytes(value)
                    else:
                        return value.decode(dbEncoding, errors='surrogateescape')
                if not PY2 and isinstance(value, bytes):
                    return value.decode('ascii', errors='surrogateescape')
            raise validators.Invalid(
                "expected a str in the StringCol '%s', got %s %r instead" % (
                    self.name, type(value), value), value, state)

        from_python = to_python

    class SOStringCol(SOStringLikeCol):

        def createValidators(self, dataType=None):
            return [StringValidator(name=self.name, dataType=dataType)] + \
                super(SOStringCol, self).createValidators()

    class StringCol(Col):
        baseClass = SOStringCol

    class NQuoted(sqlbuilder.SQLExpression):
        def __init__(self, value):
            self.value = value

        def __hash__(self):
            return hash(self.value)

        def __sqlrepr__(self, db):
            assert db == 'mssql'
            return "N" + sqlbuilder.sqlrepr(self.value, db)

    class UnicodeStringValidator(SOValidator):

        def to_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, (unicode_type, sqlbuilder.SQLExpression)):
                return value
            if isinstance(value, str):
                return value.decode(self.getDbEncoding(state))
            if isinstance(value, array):  # MySQL
                return value.tostring().decode(self.getDbEncoding(state))
            if hasattr(value, '__unicode__'):
                return unicode(value)
            raise validators.Invalid(
                "expected a str or a unicode in the UnicodeCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

        def from_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, (str, sqlbuilder.SQLExpression)):
                return value
            if isinstance(value, unicode_type):
                try:
                    connection = state.connection or state.soObject._connection
                except AttributeError:
                    pass
                else:
                    if connection.dbName == 'mssql':
                        if PY2:
                            value = value.encode(self.getDbEncoding(state))
                        return NQuoted(value)
                return value.encode(self.getDbEncoding(state))
            if hasattr(value, '__unicode__'):
                return unicode(value).encode(self.getDbEncoding(state))
            raise validators.Invalid(
                "expected a str or a unicode in the UnicodeCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

    class SOUnicodeCol(SOStringLikeCol):
        def _mssqlType(self):
            if self.customSQLType is not None:
                return self.customSQLType
            return 'N' + super(SOUnicodeCol, self)._mssqlType()

        def createValidators(self):
            return [UnicodeStringValidator(name=self.name)] + \
                super(SOUnicodeCol, self).createValidators()

    class UnicodeCol(Col):
        baseClass = SOUnicodeCol

    class IntValidator(SOValidator):

        def to_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, (int, long, sqlbuilder.SQLExpression)):
                return value
            for converter, attr_name in (int, '__int__'), (long, '__long__'):
                if hasattr(value, attr_name):
                    try:
                        return converter(value)
                    except Exception:
                        break
            raise validators.Invalid(
                "expected an int in the IntCol '%s', got %s %r instead" % (
                    self.name, type(value), value), value, state)

        from_python = to_python

    class SOIntCol(SOCol):
        # 3-03 @@: support precision, maybe max and min directly
        def __init__(self, **kw):
            self.length = kw.pop('length', None)
            self.unsigned = bool(kw.pop('unsigned', None))
            self.zerofill = bool(kw.pop('zerofill', None))
            SOCol.__init__(self, **kw)

        def autoConstraints(self):
            return [constrs.isInt]

        def createValidators(self):
            return [IntValidator(name=self.name)] + \
                super(SOIntCol, self).createValidators()

        def addSQLAttrs(self, str):
            _ret = str
            if str is None or len(str) < 1:
                return None

            if self.length and self.length >= 1:
                _ret = "%s(%d)" % (_ret, self.length)
            if self.unsigned:
                _ret += " UNSIGNED"
            if self.zerofill:
                _ret += " ZEROFILL"
            return _ret

        def _sqlType(self):
            return self.addSQLAttrs("INT")

    class IntCol(Col):
        baseClass = SOIntCol

    class SOTinyIntCol(SOIntCol):
        def _sqlType(self):
            return self.addSQLAttrs("TINYINT")

    class TinyIntCol(Col):
        baseClass = SOTinyIntCol

    class SOSmallIntCol(SOIntCol):
        def _sqlType(self):
            return self.addSQLAttrs("SMALLINT")

    class SmallIntCol(Col):
        baseClass = SOSmallIntCol

    class SOMediumIntCol(SOIntCol):
        def _sqlType(self):
            return self.addSQLAttrs("MEDIUMINT")

    class MediumIntCol(Col):
        baseClass = SOMediumIntCol

    class SOBigIntCol(SOIntCol):
        def _sqlType(self):
            return self.addSQLAttrs("BIGINT")

    class BigIntCol(Col):
        baseClass = SOBigIntCol

    class BoolValidator(SOValidator):

        def to_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, (bool, sqlbuilder.SQLExpression)):
                return value
            if PY2 and hasattr(value, '__nonzero__') \
                    or not PY2 and hasattr(value, '__bool__'):
                return bool(value)
            try:
                connection = state.connection or state.soObject._connection
            except AttributeError:
                pass
            else:
                if connection.dbName == 'postgres' and \
                        connection.driver in ('odbc', 'pyodbc', 'pypyodbc') and \
                        isinstance(value, string_type):
                    return bool(int(value))
            raise validators.Invalid(
                "expected a bool or an int in the BoolCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

        from_python = to_python

    class SOBoolCol(SOCol):

        def autoConstraints(self):
            return [constrs.isBool]

        def createValidators(self):
            return [BoolValidator(name=self.name)] + \
                super(SOBoolCol, self).createValidators()

        def _postgresType(self):
            return 'BOOL'

        def _mysqlType(self):
            return "BOOL"

        def _sybaseType(self):
            return "BIT"

        def _mssqlType(self):
            return "BIT"

        def _firebirdType(self):
            return 'INT'

        def _maxdbType(self):
            return "BOOLEAN"

        def _sqliteType(self):
            return "BOOLEAN"

    class BoolCol(Col):
        baseClass = SOBoolCol

    class FloatValidator(SOValidator):

        def to_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, (float, int, long, sqlbuilder.SQLExpression)):
                return value
            for converter, attr_name in (
                    (float, '__float__'), (int, '__int__'), (long, '__long__')):
                if hasattr(value, attr_name):
                    try:
                        return converter(value)
                    except Exception:
                        break
            raise validators.Invalid(
                "expected a float in the FloatCol '%s', got %s %r instead" % (
                    self.name, type(value), value), value, state)

        from_python = to_python

    class SOFloatCol(SOCol):
        # 3-03 @@: support precision (e.g., DECIMAL)

        def autoConstraints(self):
            return [constrs.isFloat]

        def createValidators(self):
            return [FloatValidator(name=self.name)] + \
                super(SOFloatCol, self).createValidators()

        def _sqlType(self):
            return 'FLOAT'

        def _mysqlType(self):
            return "DOUBLE PRECISION"

    class FloatCol(Col):
        baseClass = SOFloatCol

    class SOKeyCol(SOCol):
        key_type = {int: "INT", str: "TEXT"}

        # 3-03 @@: this should have a simplified constructor
        # Should provide foreign key information for other DBs.

        def __init__(self, **kw):
            self.refColumn = kw.pop('refColumn', None)
            super(SOKeyCol, self).__init__(**kw)

        def _idType(self):
            return self.soClass.sqlmeta.idType

        def _sqlType(self):
            return self.key_type[self._idType()]

        def _sybaseType(self):
            key_type = {int: "NUMERIC(18,0)", str: "TEXT"}
            return key_type[self._idType()]

        def _mssqlType(self):
            key_type = {int: "INT", str: "TEXT"}
            return key_type[self._idType()]

        def _firebirdType(self):
            key_type = {int: "INT", str: "VARCHAR(255)"}
            return key_type[self._idType()]

    class KeyCol(Col):

        baseClass = SOKeyCol

    class ForeignKeyValidator(SOValidator):

        def __init__(self, *args, **kw):
            super(ForeignKeyValidator, self).__init__(*args, **kw)
            self.fkIDType = None

        def from_python(self, value, state):
            if value is None:
                return None
            # Avoid importing the main module
            # to get the SQLObject class for isinstance
            if hasattr(value, 'sqlmeta'):
                return value
            if self.fkIDType is None:
                otherTable = findClass(self.soCol.foreignKey,
                                       self.soCol.soClass.sqlmeta.registry)
                self.fkIDType = otherTable.sqlmeta.idType
            try:
                value = self.fkIDType(value)
                return value
            except (ValueError, TypeError):
                pass
            raise validators.Invalid("expected a %r for the ForeignKey '%s', "
                                     "got %s %r instead" %
                                     (self.fkIDType, self.name,
                                      type(value), value), value, state)

    class SOForeignKey(SOKeyCol):

        def __init__(self, **kw):
            foreignKey = kw['foreignKey']
            style = kw['soClass'].sqlmeta.style
            if kw.get('name'):
                kw['origName'] = kw['name']
                kw['name'] = style.instanceAttrToIDAttr(kw['name'])
            else:
                kw['name'] = style.instanceAttrToIDAttr(
                    style.pythonClassToAttr(foreignKey))
            super(SOForeignKey, self).__init__(**kw)

        def createValidators(self):
            return [ForeignKeyValidator(name=self.name)] + \
                super(SOForeignKey, self).createValidators()

        def _idType(self):
            other = findClass(self.foreignKey, self.soClass.sqlmeta.registry)
            return other.sqlmeta.idType

        def sqliteCreateSQL(self):
            sql = SOKeyCol.sqliteCreateSQL(self)
            other = findClass(self.foreignKey, self.soClass.sqlmeta.registry)
            tName = other.sqlmeta.table
            idName = self.refColumn or other.sqlmeta.idName
            if self.cascade is not None:
                if self.cascade == 'null':
                    action = 'ON DELETE SET NULL'
                elif self.cascade:
                    action = 'ON DELETE CASCADE'
                else:
                    action = 'ON DELETE RESTRICT'
            else:
                action = ''
            constraint = ('CONSTRAINT %(colName)s_exists '
                          # 'FOREIGN KEY(%(colName)s) '
                          'REFERENCES %(tName)s(%(idName)s) '
                          '%(action)s' %
                          {'tName': tName,
                           'colName': self.dbName,
                           'idName': idName,
                           'action': action})
            sql = ' '.join([sql, constraint])
            return sql

        def postgresCreateSQL(self):
            sql = SOKeyCol.postgresCreateSQL(self)
            return sql

        def postgresCreateReferenceConstraint(self):
            sTName = self.soClass.sqlmeta.table
            other = findClass(self.foreignKey, self.soClass.sqlmeta.registry)
            tName = other.sqlmeta.table
            idName = self.refColumn or other.sqlmeta.idName
            if self.cascade is not None:
                if self.cascade == 'null':
                    action = 'ON DELETE SET NULL'
                elif self.cascade:
                    action = 'ON DELETE CASCADE'
                else:
                    action = 'ON DELETE RESTRICT'
            else:
                action = ''
            constraint = ('ALTER TABLE %(sTName)s '
                          'ADD CONSTRAINT %(colName)s_exists '
                          'FOREIGN KEY (%(colName)s) '
                          'REFERENCES %(tName)s (%(idName)s) '
                          '%(action)s' %
                          {'tName': tName,
                           'colName': self.dbName,
                           'idName': idName,
                           'action': action,
                           'sTName': sTName})
            return constraint

        def mysqlCreateReferenceConstraint(self):
            sTName = self.soClass.sqlmeta.table
            sTLocalName = sTName.split('.')[-1]
            other = findClass(self.foreignKey, self.soClass.sqlmeta.registry)
            tName = other.sqlmeta.table
            idName = self.refColumn or other.sqlmeta.idName
            if self.cascade is not None:
                if self.cascade == 'null':
                    action = 'ON DELETE SET NULL'
                elif self.cascade:
                    action = 'ON DELETE CASCADE'
                else:
                    action = 'ON DELETE RESTRICT'
            else:
                action = ''
            constraint = ('ALTER TABLE %(sTName)s '
                          'ADD CONSTRAINT %(sTLocalName)s_%(colName)s_exists '
                          'FOREIGN KEY (%(colName)s) '
                          'REFERENCES %(tName)s (%(idName)s) '
                          '%(action)s' %
                          {'tName': tName,
                           'colName': self.dbName,
                           'idName': idName,
                           'action': action,
                           'sTName': sTName,
                           'sTLocalName': sTLocalName})
            return constraint

        def mysqlCreateSQL(self, connection=None):
            return SOKeyCol.mysqlCreateSQL(self, connection)

        def sybaseCreateSQL(self):
            sql = SOKeyCol.sybaseCreateSQL(self)
            other = findClass(self.foreignKey, self.soClass.sqlmeta.registry)
            tName = other.sqlmeta.table
            idName = self.refColumn or other.sqlmeta.idName
            reference = ('REFERENCES %(tName)s(%(idName)s) ' %
                         {'tName': tName,
                          'idName': idName})
            sql = ' '.join([sql, reference])
            return sql

        def sybaseCreateReferenceConstraint(self):
            # @@: Code from above should be moved here
            return None

        def mssqlCreateSQL(self, connection=None):
            sql = SOKeyCol.mssqlCreateSQL(self, connection)
            other = findClass(self.foreignKey, self.soClass.sqlmeta.registry)
            tName = other.sqlmeta.table
            idName = self.refColumn or other.sqlmeta.idName
            reference = ('REFERENCES %(tName)s(%(idName)s) ' %
                         {'tName': tName,
                          'idName': idName})
            sql = ' '.join([sql, reference])
            return sql

        def mssqlCreateReferenceConstraint(self):
            # @@: Code from above should be moved here
            return None

        def maxdbCreateSQL(self):
            other = findClass(self.foreignKey, self.soClass.sqlmeta.registry)
            fidName = self.dbName
            # I assume that foreign key name is identical
            # to the id of the reference table
            sql = ' '.join([fidName, self._maxdbType()])
            tName = other.sqlmeta.table
            idName = self.refColumn or other.sqlmeta.idName
            sql += ',\nFOREIGN KEY (%s) REFERENCES %s(%s)' % (fidName, tName,
                                                              idName)
            return sql

        def maxdbCreateReferenceConstraint(self):
            # @@: Code from above should be moved here
            return None

    class ForeignKey(KeyCol):

        baseClass = SOForeignKey

        def __init__(self, foreignKey=None, **kw):
            super(ForeignKey, self).__init__(foreignKey=foreignKey, **kw)

    class EnumValidator(SOValidator):

        def to_python(self, value, state):
            if value in self.enumValues:
                # Only encode on python 2 - on python 3, the database driver
                # will handle this
                if isinstance(value, unicode_type) and PY2:
                    dbEncoding = self.getDbEncoding(state)
                    value = value.encode(dbEncoding)
                return value
            elif not self.notNone and value is None:
                return None
            raise validators.Invalid(
                "expected a member of %r in the EnumCol '%s', got %r instead" % (
                    self.enumValues, self.name, value), value, state)

        from_python = to_python

    class SOEnumCol(SOCol):

        def __init__(self, **kw):
            self.enumValues = kw.pop('enumValues', None)
            assert self.enumValues is not None, \
                'You must provide an enumValues keyword argument'
            super(SOEnumCol, self).__init__(**kw)

        def autoConstraints(self):
            return [constrs.isString, constrs.InList(self.enumValues)]

        def createValidators(self):
            return [EnumValidator(name=self.name, enumValues=self.enumValues,
                                  notNone=self.notNone)] + \
                super(SOEnumCol, self).createValidators()

        def _mysqlType(self):
            # We need to map None in the enum expression to an appropriate
            # condition on NULL
            if None in self.enumValues:
                return "ENUM(%s)" % ', '.join(
                    [sqlbuilder.sqlrepr(v, 'mysql') for v in self.enumValues
                        if v is not None])
            else:
                return "ENUM(%s) NOT NULL" % ', '.join(
                    [sqlbuilder.sqlrepr(v, 'mysql') for v in self.enumValues])

        def _postgresType(self):
            length = max(map(self._getlength, self.enumValues))
            enumValues = ', '.join(
                [sqlbuilder.sqlrepr(v, 'postgres') for v in self.enumValues])
            checkConstraint = "CHECK (%s in (%s))" % (self.dbName, enumValues)
            return "VARCHAR(%i) %s" % (length, checkConstraint)

        _sqliteType = _postgresType

        def _sybaseType(self):
            return self._postgresType()

        def _mssqlType(self):
            return self._postgresType()

        def _firebirdType(self):
            length = max(map(self._getlength, self.enumValues))
            enumValues = ', '.join(
                [sqlbuilder.sqlrepr(v, 'firebird') for v in self.enumValues])
            checkConstraint = "CHECK (%s in (%s))" % (self.dbName, enumValues)
            # NB. Return a tuple, not a string here
            return "VARCHAR(%i)" % (length), checkConstraint

        def _maxdbType(self):
            raise TypeError("Enum type is not supported on MAX DB")

        def _getlength(self, obj):
            """
            None counts as 0; everything else uses len()
            """
            if obj is None:
                return 0
            else:
                return len(obj)

    class EnumCol(Col):
        baseClass = SOEnumCol

    class SetValidator(SOValidator):
        """
        Translates Python tuples into SQL comma-delimited SET strings.
        """

        def to_python(self, value, state):
            if isinstance(value, str):
                return tuple(value.split(","))
            raise validators.Invalid(
                "expected a string in the SetCol '%s', got %s %r instead" % (
                    self.name, type(value), value), value, state)

        def from_python(self, value, state):
            if isinstance(value, string_type):
                value = (value,)
            try:
                return ",".join(value)
            except Exception:
                raise validators.Invalid(
                    "expected a string or a sequence of strings "
                    "in the SetCol '%s', got %s %r instead" % (
                        self.name, type(value), value), value, state)

    class SOSetCol(SOCol):
        def __init__(self, **kw):
            self.setValues = kw.pop('setValues', None)
            assert self.setValues is not None, \
                'You must provide a setValues keyword argument'
            super(SOSetCol, self).__init__(**kw)

        def autoConstraints(self):
            return [constrs.isString, constrs.InList(self.setValues)]

        def createValidators(self):
            return [SetValidator(name=self.name, setValues=self.setValues)] + \
                super(SOSetCol, self).createValidators()

        def _mysqlType(self):
            return "SET(%s)" % ', '.join(
                [sqlbuilder.sqlrepr(v, 'mysql') for v in self.setValues])

    class SetCol(Col):
        baseClass = SOSetCol

    class DateTimeValidator(validators.DateValidator):
        def to_python(self, value, state):
            if value is None:
                return None
            if isinstance(value,
                          (datetime.datetime, datetime.date,
                           datetime.time, sqlbuilder.SQLExpression)):
                return value
            if mxdatetime_available:
                if isinstance(value, mxDateTimeType):
                    # convert mxDateTime instance to datetime
                    if (self.format.find("%H") >= 0) or \
                       (self.format.find("%T")) >= 0:
                        return datetime.datetime(value.year, value.month,
                                                 value.day,
                                                 value.hour, value.minute,
                                                 int(value.second))
                    else:
                        return datetime.date(value.year, value.month, value.day)
                elif isinstance(value, mxTimeType):
                    # convert mxTime instance to time
                    if self.format.find("%d") >= 0:
                        return datetime.timedelta(seconds=value.seconds)
                    else:
                        return datetime.time(value.hour, value.minute,
                                             int(value.second))
            if zope_datetime_available:
                if isinstance(value, zopeDateTimeType):
                    # convert zopeDateTime instance to datetime
                    if (self.format.find("%H") >= 0) or \
                       (self.format.find("%T")) >= 0:
                        return datetime.datetime(
                            value.year(), value.month(), value.day(),
                            value.hour(), value.minute(), int(value.second()))
                    else:
                        return datetime.date(value.year, value.month, value.day)
            try:
                if self.format.find(".%f") >= 0:
                    if '.' in value:
                        _value = value.split('.')
                        microseconds = _value[-1]
                        _l = len(microseconds)
                        if _l < 6:
                            _value[-1] = microseconds + '0' * (6 - _l)
                        elif _l > 6:
                            _value[-1] = microseconds[:6]
                        if _l != 6:
                            value = '.'.join(_value)
                    else:
                        value += '.0'
                return datetime.datetime.strptime(value, self.format)
            except Exception:
                raise validators.Invalid(
                    "expected a date/time string of the '%s' format "
                    "in the DateTimeCol '%s', got %s %r instead" % (
                        self.format, self.name, type(value), value), value, state)

        def from_python(self, value, state):
            if value is None:
                return None
            if isinstance(value,
                          (datetime.datetime, datetime.date,
                           datetime.time, sqlbuilder.SQLExpression)):
                return value
            if hasattr(value, "strftime"):
                return value.strftime(self.format)
            raise validators.Invalid(
                "expected a datetime in the DateTimeCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

    if mxdatetime_available:
        class MXDateTimeValidator(validators.DateValidator):
            def to_python(self, value, state):
                if value is None:
                    return None
                if isinstance(value,
                              (mxDateTimeType, mxTimeType,
                               sqlbuilder.SQLExpression)):
                    return value
                if isinstance(value, datetime.datetime):
                    return mxDateTime.DateTime(value.year, value.month, value.day,
                                               value.hour, value.minute,
                                               value.second)
                elif isinstance(value, datetime.date):
                    return mxDateTime.Date(value.year, value.month, value.day)
                elif isinstance(value, datetime.time):
                    return mxDateTime.Time(value.hour, value.minute, value.second)
                elif isinstance(value, datetime.timedelta):
                    if value.days:
                        raise validators.Invalid(
                            "the value for the TimeCol '%s' must has days=0, "
                            "it has days=%d" % (self.name, value.days),
                            value, state)
                    return mxDateTime.Time(seconds=value.seconds)
                if zope_datetime_available:
                    if isinstance(value, zopeDateTimeType):
                        # convert zopeDateTime instance to mxdatetime
                        return mxDateTime.DateTime(
                            value.year(), value.month(), value.day(),
                            value.hour(), value.minute(), int(value.second()))
                try:
                    if self.format.find(".%f") >= 0:
                        if '.' in value:
                            _value = value.split('.')
                            microseconds = _value[-1]
                            _l = len(microseconds)
                            if _l < 6:
                                _value[-1] = microseconds + '0' * (6 - _l)
                            elif _l > 6:
                                _value[-1] = microseconds[:6]
                            if _l != 6:
                                value = '.'.join(_value)
                        else:
                            value += '.0'
                    value = datetime.datetime.strptime(value, self.format)
                    return mxDateTime.DateTime(value.year, value.month, value.day,
                                               value.hour, value.minute,
                                               value.second)
                except Exception:
                    raise validators.Invalid(
                        "expected a date/time string of the '%s' format "
                        "in the DateTimeCol '%s', got %s %r instead" % (
                            self.format, self.name, type(value), value),
                        value, state)

            def from_python(self, value, state):
                if value is None:
                    return None
                if isinstance(value,
                              (mxDateTimeType, mxTimeType,
                               sqlbuilder.SQLExpression)):
                    return value
                if hasattr(value, "strftime"):
                    return value.strftime(self.format)
                raise validators.Invalid(
                    "expected a mxDateTime in the DateTimeCol '%s', "
                    "got %s %r instead" % (
                        self.name, type(value), value), value, state)

    if zope_datetime_available:
        class ZopeDateTimeValidator(validators.DateValidator):
            def to_python(self, value, state):
                if value is None:
                    return None
                if isinstance(value,
                              (zopeDateTimeType, sqlbuilder.SQLExpression)):
                    return value
                if isinstance(value, datetime.datetime):
                    return zopeDateTime.DateTime(
                        value.year, value.month, value.day,
                        value.hour, value.minute, value.second)
                elif isinstance(value, datetime.date):
                    return zopeDateTime.DateTime(
                        value.year, value.month, value.day)
                elif isinstance(value, datetime.time):
                    return zopeDateTime.DateTime(
                        value.hour, value.minute, value.second)
                elif isinstance(value, datetime.timedelta):
                    if value.days:
                        raise validators.Invalid(
                            "the value for the TimeCol '%s' must has days=0, "
                            "it has days=%d" % (self.name, value.days),
                            value, state)
                    return zopeDateTime.DateTime(seconds=value.seconds)
                if mxdatetime_available:
                    if isinstance(value, mxDateTimeType):
                        # convert mxDateTime instance to zopeDateTime
                        return zopeDateTime.DateTime(
                            value.year, value.month, value.day,
                            value.hour, value.minute, value.second)
                try:
                    if self.format.find(".%f") >= 0:
                        if '.' in value:
                            _value = value.split('.')
                            microseconds = _value[-1]
                            _l = len(microseconds)
                            if _l < 6:
                                _value[-1] = microseconds + '0' * (6 - _l)
                            elif _l > 6:
                                _value[-1] = microseconds[:6]
                            if _l != 6:
                                value = '.'.join(_value)
                        else:
                            value += '.0'
                    value = datetime.datetime.strptime(value, self.format)
                    return zopeDateTime.DateTime(
                        value.year, value.month, value.day,
                        value.hour, value.minute, value.second)
                except Exception:
                    raise validators.Invalid(
                        "expected a date/time string of the '%s' format "
                        "in the DateTimeCol '%s', got %s %r instead" % (
                            self.format, self.name, type(value), value),
                        value, state)

            def from_python(self, value, state):
                if value is None:
                    return None
                if isinstance(value,
                              (zopeDateTimeType, sqlbuilder.SQLExpression)):
                    return value
                if hasattr(value, "strftime"):
                    return value.strftime(self.format)
                raise validators.Invalid(
                    "expected a zopeDateTime in the DateTimeCol '%s', "
                    "got %s %r instead" % (
                        self.name, type(value), value), value, state)

    class SODateTimeCol(SOCol):
        datetimeFormat = '%Y-%m-%d %H:%M:%S.%f'

        def __init__(self, **kw):
            datetimeFormat = kw.pop('datetimeFormat', None)
            if datetimeFormat:
                self.datetimeFormat = datetimeFormat
            super(SODateTimeCol, self).__init__(**kw)

        def createValidators(self):
            _validators = super(SODateTimeCol, self).createValidators()
            if default_datetime_implementation == DATETIME_IMPLEMENTATION:
                validatorClass = DateTimeValidator
            elif default_datetime_implementation == MXDATETIME_IMPLEMENTATION:
                validatorClass = MXDateTimeValidator
            elif default_datetime_implementation == ZOPE_DATETIME_IMPLEMENTATION:
                validatorClass = ZopeDateTimeValidator
            if default_datetime_implementation:
                _validators.insert(0, validatorClass(name=self.name,
                                                     format=self.datetimeFormat))
            return _validators

        def _mysqlType(self):
            if self.connection and self.connection.can_use_microseconds():
                return 'DATETIME(6)'
            else:
                return 'DATETIME'

        def _postgresType(self):
            return 'TIMESTAMP'

        def _sybaseType(self):
            return 'DATETIME'

        def _mssqlType(self):
            if self.connection and self.connection.can_use_microseconds():
                return 'DATETIME2(6)'
            else:
                return 'DATETIME'

        def _sqliteType(self):
            return 'TIMESTAMP'

        def _firebirdType(self):
            return 'TIMESTAMP'

        def _maxdbType(self):
            return 'TIMESTAMP'

    class DateTimeCol(Col):
        baseClass = SODateTimeCol

        @staticmethod
        def now():
            if default_datetime_implementation == DATETIME_IMPLEMENTATION:
                return datetime.datetime.now()
            elif default_datetime_implementation == MXDATETIME_IMPLEMENTATION:
                return mxDateTime.now()
            elif default_datetime_implementation == ZOPE_DATETIME_IMPLEMENTATION:
                return zopeDateTime.DateTimr()
            else:
                assert 0, ("No datetime implementation available "
                           "(DATETIME_IMPLEMENTATION=%r)"
                           % DATETIME_IMPLEMENTATION)

    class DateValidator(DateTimeValidator):
        def to_python(self, value, state):
            if isinstance(value, datetime.datetime):
                value = value.date()
            if isinstance(value, (datetime.date, sqlbuilder.SQLExpression)):
                return value
            value = super(DateValidator, self).to_python(value, state)
            if isinstance(value, datetime.datetime):
                value = value.date()
            return value

        from_python = to_python

    class SODateCol(SOCol):
        dateFormat = '%Y-%m-%d'

        def __init__(self, **kw):
            dateFormat = kw.pop('dateFormat', None)
            if dateFormat:
                self.dateFormat = dateFormat
            super(SODateCol, self).__init__(**kw)

        def createValidators(self):
            """Create a validator for the column.

            Can be overriden in descendants.

            """
            _validators = super(SODateCol, self).createValidators()
            if default_datetime_implementation == DATETIME_IMPLEMENTATION:
                validatorClass = DateValidator
            elif default_datetime_implementation == MXDATETIME_IMPLEMENTATION:
                validatorClass = MXDateTimeValidator
            elif default_datetime_implementation == ZOPE_DATETIME_IMPLEMENTATION:
                validatorClass = ZopeDateTimeValidator
            if default_datetime_implementation:
                _validators.insert(0, validatorClass(name=self.name,
                                                     format=self.dateFormat))
            return _validators

        def _mysqlType(self):
            return 'DATE'

        def _postgresType(self):
            return 'DATE'

        def _sybaseType(self):
            return self._postgresType()

        def _mssqlType(self):
            """
            SQL Server doesn't have  a DATE data type, to emulate we use a vc(10)
            """
            return 'VARCHAR(10)'

        def _firebirdType(self):
            return 'DATE'

        def _maxdbType(self):
            return 'DATE'

        def _sqliteType(self):
            return 'DATE'

    class DateCol(Col):
        baseClass = SODateCol

    class TimeValidator(DateTimeValidator):
        def to_python(self, value, state):
            if isinstance(value, (datetime.time, sqlbuilder.SQLExpression)):
                return value
            if isinstance(value, datetime.timedelta):
                if value.days:
                    raise validators.Invalid(
                        "the value for the TimeCol '%s' must has days=0, "
                        "it has days=%d" % (self.name, value.days), value, state)
                return datetime.time(
                    *time.gmtime(value.seconds)[3:6],
                    microsecond=value.microseconds
                )
            value = super(TimeValidator, self).to_python(value, state)
            if isinstance(value, datetime.datetime):
                value = value.time()
            return value

        from_python = to_python

    class SOTimeCol(SOCol):
        timeFormat = '%H:%M:%S.%f'

        def __init__(self, **kw):
            timeFormat = kw.pop('timeFormat', None)
            if timeFormat:
                self.timeFormat = timeFormat
            super(SOTimeCol, self).__init__(**kw)

        def createValidators(self):
            _validators = super(SOTimeCol, self).createValidators()
            if default_datetime_implementation == DATETIME_IMPLEMENTATION:
                validatorClass = TimeValidator
            elif default_datetime_implementation == MXDATETIME_IMPLEMENTATION:
                validatorClass = MXDateTimeValidator
            elif default_datetime_implementation == ZOPE_DATETIME_IMPLEMENTATION:
                validatorClass = ZopeDateTimeValidator
            if default_datetime_implementation:
                _validators.insert(0, validatorClass(name=self.name,
                                                     format=self.timeFormat))
            return _validators

        def _mysqlType(self):
            if self.connection and self.connection.can_use_microseconds():
                return 'TIME(6)'
            else:
                return 'TIME'

        def _postgresType(self):
            return 'TIME'

        def _sybaseType(self):
            return 'TIME'

        def _mssqlType(self):
            if self.connection and self.connection.can_use_microseconds():
                return 'TIME(6)'
            else:
                return 'TIME'

        def _sqliteType(self):
            return 'TIME'

        def _firebirdType(self):
            return 'TIME'

        def _maxdbType(self):
            return 'TIME'

    class TimeCol(Col):
        baseClass = SOTimeCol

    class SOTimestampCol(SODateTimeCol):
        """
        Necessary to support MySQL's use of TIMESTAMP versus DATETIME types
        """

        def __init__(self, **kw):
            if 'default' not in kw:
                kw['default'] = None
            SOCol.__init__(self, **kw)

        def _mysqlType(self):
            if self.connection and self.connection.can_use_microseconds():
                return 'TIMESTAMP(6)'
            else:
                return 'TIMESTAMP'

    class TimestampCol(Col):
        baseClass = SOTimestampCol

    class TimedeltaValidator(SOValidator):
        def to_python(self, value, state):
            return value

        from_python = to_python

    class SOTimedeltaCol(SOCol):
        def _postgresType(self):
            return 'INTERVAL'

        def createValidators(self):
            return [TimedeltaValidator(name=self.name)] + \
                super(SOTimedeltaCol, self).createValidators()

    class TimedeltaCol(Col):
        baseClass = SOTimedeltaCol

    class DecimalValidator(SOValidator):
        def to_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, (int, long, Decimal, sqlbuilder.SQLExpression)):
                return value
            if isinstance(value, float):
                value = str(value)
            try:
                connection = state.connection or state.soObject._connection
            except AttributeError:
                pass
            else:
                if hasattr(connection, "decimalSeparator"):
                    value = value.replace(connection.decimalSeparator, ".")
            try:
                return Decimal(value)
            except Exception:
                raise validators.Invalid(
                    "expected a Decimal in the DecimalCol '%s', "
                    "got %s %r instead" % (
                        self.name, type(value), value), value, state)

        def from_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, float):
                value = str(value)
            if isinstance(value, string_type):
                try:
                    connection = state.connection or state.soObject._connection
                except AttributeError:
                    pass
                else:
                    if hasattr(connection, "decimalSeparator"):
                        value = value.replace(connection.decimalSeparator, ".")
                try:
                    return Decimal(value)
                except Exception:
                    raise validators.Invalid(
                        "can not parse Decimal value '%s' "
                        "in the DecimalCol from '%s'" % (
                            value, getattr(state, 'soObject', '(unknown)')),
                        value, state)
            if isinstance(value, (int, long, Decimal, sqlbuilder.SQLExpression)):
                return value
            raise validators.Invalid(
                "expected a Decimal in the DecimalCol '%s', got %s %r instead" % (
                    self.name, type(value), value), value, state)

    class SODecimalCol(SOCol):

        def __init__(self, **kw):
            self.size = kw.pop('size', NoDefault)
            assert self.size is not NoDefault, \
                "You must give a size argument"
            self.precision = kw.pop('precision', NoDefault)
            assert self.precision is not NoDefault, \
                "You must give a precision argument"
            super(SODecimalCol, self).__init__(**kw)

        def _sqlType(self):
            return 'DECIMAL(%i, %i)' % (self.size, self.precision)

        def createValidators(self):
            return [DecimalValidator(name=self.name)] + \
                super(SODecimalCol, self).createValidators()

    class DecimalCol(Col):
        baseClass = SODecimalCol

    class SOCurrencyCol(SODecimalCol):

        def __init__(self, **kw):
            pushKey(kw, 'size', 10)
            pushKey(kw, 'precision', 2)
            super(SOCurrencyCol, self).__init__(**kw)

    class CurrencyCol(DecimalCol):
        baseClass = SOCurrencyCol

    class DecimalStringValidator(DecimalValidator):
        def to_python(self, value, state):
            value = super(DecimalStringValidator, self).to_python(value, state)
            if self.precision and isinstance(value, Decimal):
                assert value < self.max, \
                    "Value must be less than %s" % int(self.max)
                value = value.quantize(self.precision)
            return value

        def from_python(self, value, state):
            value = super(DecimalStringValidator, self).from_python(value, state)
            if isinstance(value, Decimal):
                if self.precision:
                    assert value < self.max, \
                        "Value must be less than %s" % int(self.max)
                    value = value.quantize(self.precision)
                value = value.to_eng_string()
            elif isinstance(value, (int, long)):
                value = str(value)
            return value

    class SODecimalStringCol(SOStringCol):
        def __init__(self, **kw):
            self.size = kw.pop('size', NoDefault)
            assert (self.size is not NoDefault) and (self.size >= 0), \
                "You must give a size argument as a positive integer"
            self.precision = kw.pop('precision', NoDefault)
            assert (self.precision is not NoDefault) and (self.precision >= 0), \
                "You must give a precision argument as a positive integer"
            kw['length'] = int(self.size) + int(self.precision)
            self.quantize = kw.pop('quantize', False)
            assert isinstance(self.quantize, bool), \
                "quantize argument must be Boolean True/False"
            super(SODecimalStringCol, self).__init__(**kw)

        def createValidators(self):
            if self.quantize:
                v = DecimalStringValidator(
                    name=self.name,
                    precision=Decimal(10) ** (-1 * int(self.precision)),
                    max=Decimal(10) ** (int(self.size) - int(self.precision)))
            else:
                v = DecimalStringValidator(name=self.name, precision=0)
            return [v] + \
                super(SODecimalStringCol, self).createValidators(dataType=Decimal)

    class DecimalStringCol(StringCol):
        baseClass = SODecimalStringCol

    class BinaryValidator(SOValidator):
        """
        Validator for binary types.

        We're assuming that the per-database modules provide some form
        of wrapper type for binary conversion.
        """

        _cachedValue = None

        def to_python(self, value, state):
            if value is None:
                return None
            try:
                connection = state.connection or state.soObject._connection
            except AttributeError:
                dbName = None
                binaryType = type(None)  # Just a simple workaround
            else:
                dbName = connection.dbName
                binaryType = connection._binaryType
            if isinstance(value, str):
                if not PY2 and dbName == "mysql":
                    value = value.encode('ascii', errors='surrogateescape')
                if dbName == "sqlite":
                    if not PY2:
                        value = bytes(value, 'ascii')
                    value = connection.module.decode(value)
                return value
            if isinstance(value, bytes):
                return value
            if isinstance(value, (buffer_type, binaryType)):
                cachedValue = self._cachedValue
                if cachedValue and cachedValue[1] == value:
                    return cachedValue[0]
                if isinstance(value, array):  # MySQL
                    return value.tostring()
                if not PY2 and isinstance(value, memoryview):
                    return value.tobytes()
                return str(value)  # buffer => string
            raise validators.Invalid(
                "expected a string in the BLOBCol '%s', got %s %r instead" % (
                    self.name, type(value), value), value, state)

        def from_python(self, value, state):
            if value is None:
                return None
            connection = state.connection or state.soObject._connection
            binary = connection.createBinary(value)
            if not PY2 and isinstance(binary, memoryview):
                binary = str(binary.tobytes(), 'ascii')
            self._cachedValue = (value, binary)
            return binary

    class SOBLOBCol(SOStringCol):
        def __init__(self, **kw):
            # Change the default from 'auto' to False -
            # this is a (mostly) binary column
            if 'varchar' not in kw:
                kw['varchar'] = False
            super(SOBLOBCol, self).__init__(**kw)

        def createValidators(self):
            return [BinaryValidator(name=self.name)] + \
                super(SOBLOBCol, self).createValidators()

        def _mysqlType(self):
            length = self.length
            varchar = self.varchar
            if length:
                if length >= 2 ** 24:
                    return varchar and "LONGTEXT" or "LONGBLOB"
                if length >= 2 ** 16:
                    return varchar and "MEDIUMTEXT" or "MEDIUMBLOB"
                if length >= 2 ** 8:
                    return varchar and "TEXT" or "BLOB"
            return varchar and "TINYTEXT" or "TINYBLOB"

        def _postgresType(self):
            return 'BYTEA'

        def _mssqlType(self):
            if self.connection and self.connection.can_use_max_types():
                return 'VARBINARY(MAX)'
            else:
                return "IMAGE"

    class BLOBCol(StringCol):
        baseClass = SOBLOBCol

    class PickleValidator(BinaryValidator):
        """
        Validator for pickle types.  A pickle type is simply a binary type
        with hidden pickling, so that we can simply store any kind of
        stuff in a particular column.

        The support for this relies directly on the support for binary for
        your database.
        """

        def to_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, unicode_type):
                dbEncoding = self.getDbEncoding(state, default='ascii')
                if PY2:
                    value = value.encode(dbEncoding)
                else:
                    value = value.encode(dbEncoding, errors='surrogateescape')
            if isinstance(value, bytes):
                return pickle.loads(value)
            raise validators.Invalid(
                "expected a pickle string in the PickleCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

        def from_python(self, value, state):
            if value is None:
                return None
            return pickle.dumps(value, self.pickleProtocol)

    class SOPickleCol(SOBLOBCol):

        def __init__(self, **kw):
            self.pickleProtocol = kw.pop('pickleProtocol', pickle.HIGHEST_PROTOCOL)
            super(SOPickleCol, self).__init__(**kw)

        def createValidators(self):
            return [PickleValidator(name=self.name,
                    pickleProtocol=self.pickleProtocol)] + \
                super(SOPickleCol, self).createValidators()

        def _mysqlType(self):
            length = self.length
            if length:
                if length >= 2 ** 24:
                    return "LONGBLOB"
                if length >= 2 ** 16:
                    return "MEDIUMBLOB"
            return "BLOB"

    class PickleCol(BLOBCol):
        baseClass = SOPickleCol

    class UuidValidator(SOValidator):

        def to_python(self, value, state):
            if value is None:
                return None
            if PY2 and isinstance(value, unicode):
                value = value.encode('ascii')
            if isinstance(value, str):
                return UUID(value)
            if isinstance(value, UUID):
                return value
            raise validators.Invalid(
                "expected string in the UuidCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

        def from_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, str):
                return value
            if isinstance(value, UUID):
                return str(value)
            raise validators.Invalid(
                "expected uuid in the UuidCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

    class SOUuidCol(SOCol):

        def createValidators(self):
            return [UuidValidator(name=self.name)] + \
                super(SOUuidCol, self).createValidators()

        def _sqlType(self):
            return 'VARCHAR(36)'

        def _postgresType(self):
            return 'UUID'

    class UuidCol(Col):
        baseClass = SOUuidCol

    class JsonbValidator(SOValidator):

        def to_python(self, value, state):
            if isinstance(value, string_type):
                return json.loads(value)
            return value

        def from_python(self, value, state):
            if value is None:
                return json.dumps(None)
            if isinstance(value, (dict, list, unicode, int, long, float, bool)):
                return json.dumps(value)
            raise validators.Invalid(
                "expect one of the following types "
                "(dict, list, unicode, int, long, float, bool) for '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

    class SOJsonbCol(SOCol):

        def createValidators(self):
            return [JsonbValidator(name=self.name)] + \
                super(SOJsonbCol, self).createValidators()

        def _postgresType(self):
            return 'JSONB'

    class JsonbCol(Col):
        baseClass = SOJsonbCol

    class JSONValidator(SOValidator):

        def to_python(self, value, state):
            if value is None:
                return None
            if isinstance(value, (bool, int, float, long, dict, list)):
                return value
            if isinstance(value, string_type):
                return json.loads(value)
            raise validators.Invalid(
                "expected a JSON str in the JSONCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

        def from_python(self, value, state):
            if value is None:
                return None
            if isinstance(value,
                          (bool, int, float, long, dict, list, string_type)):
                return json.dumps(value)
            raise validators.Invalid(
                "expected an object suitable for JSON in the JSONCol '%s', "
                "got %s %r instead" % (
                    self.name, type(value), value), value, state)

    class SOJSONCol(SOStringCol):

        def createValidators(self):
            return [JSONValidator(name=self.name)]

        # Doesn't work, especially with Postgres
        # def _sqlType(self):
        #     return 'JSON'

    class JSONCol(StringCol):
        baseClass = SOJSONCol

    #############################################
    #
    # Added by Tippett
    #

    #
    # Convenience stuff Monkey-Patched onto sqlbuilder.SQLObjectField,
    # so you can do:
    #
    #   Table.q.column.json_extract("key") == value
    #   Table.q.column.json_contains("item")
    #   Table.q.column.json_length("key")
    #
    # instead of
    #
    #   func.JSON_EXTRACT(Table.q.column, '$.key') == value
    #   func.JSON_CONTAINS(Table.q.column, json.dumps("item"))
    #   func.JSON_LENGTH(Table.q.column, '$.key')
    #

    def _json_extract(col, key, path=None):
        """
        """
        assert isinstance(col.column, SOJSONCol), \
            "{!r} is not a JSONCol".format(col)
        if path is None:
            return sqlbuilder.func.JSON_EXTRACT(col, '$.%s' % key)
        else:
            return sqlbuilder.func.JSON_EXTRACT(col, '$.%s' % key, path)

    def _json_contains(col, value, path=None):
        assert isinstance(col.column, SOJSONCol), \
            "{!r} is not a JSONCol".format(col)
        if path is None:
            return sqlbuilder.func.JSON_CONTAINS(col, json.dumps(value))
        else:
            return sqlbuilder.func.JSON_CONTAINS(col, json.dumps(value), path)

    def _json_length(col, path=None):
        assert isinstance(col.column, SOJSONCol), \
            "{!r} is not a JSONCol".format(col)
        if path is None:
            return sqlbuilder.func.JSON_LENGTH(col)
        else:
            return sqlbuilder.func.JSON_LENGTH(col, path)

    sqlbuilder.SQLObjectField.json_extract = _json_extract
    sqlbuilder.SQLObjectField.json_contains = _json_contains
    sqlbuilder.SQLObjectField.json_length = _json_length

    def pushKey(kw, name, value):
        if name not in kw:
            kw[name] = value

    all = []
    # Use copy() to avoid 'dictionary changed' issues on python 3
    for key, value in globals().copy().items():
        if isinstance(value, type) and (issubclass(value, (Col, SOCol))):
            all.append(key)
    __all__.extend(all)
    del all