SQLGenerator.py :  » Web-Frameworks » Webware » Webware-1.0.2 » MiddleKit » Design » Python Open Source

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Python Open Source » Web Frameworks » Webware 
Webware » Webware 1.0.2 » MiddleKit » Design » SQLGenerator.py
import os, sys, types
from glob import glob
from time import asctime,localtime,time
from MiddleKit.Core.ObjRefAttr import objRefJoin
from MiscUtils import AbstractError,StringTypes,CSVParser
from CodeGenerator import *

try: # for Python < 2.3
  True, False
except NameError:
  True, False = 1, 0


class SampleError(Exception):

  def __init__(self, line, error):
    self._line = line
    self._error = error

  def write(self, filename):
    print '%s:%d: %s' % (filename, self._line, self._error)


class SQLGenerator(CodeGenerator):
  """The MiddleKit SQL Generator class.

  This class and its associated mix-ins are responsible for generating:
    - Create.sql
    - InsertSample.sql
    - Info.text

  A subclass and further mix-ins are required for specific databases
  (since SQL varies from product to product).

  The main method to invoke is generate():

    gen = SomeSQLGenerator()
    gen.readModelFileNamed(filename)
    gen.generate(dirname)

  For subclassers:
    - Subclasses should be named <DATABASE>SQLGenerator where <DATABASE>
      is the name of the particular database product.
    - A good example of a custom subclass is MySQLSQLGenerator.py.
      Be sure to take a look at it.
    - Candidates for customization include:
      Klasses
        dropDatabaseSQL()
        createDatabaseSQL()
        useDatabaseSQL()
      StringAttr
      EnumAttr
  """

  def sqlDatabaseName(self):
    """Return the name of the database by asking the generator's model."""
    return self.model().sqlDatabaseName()

  def generate(self, dirname):
    self.requireDir(dirname)
    self.writeInfoFile(os.path.join(dirname, 'Info.text'))
    self._model.writeCreateSQL(self, dirname)
    self._model.writeInsertSamplesSQL(self, dirname)

  def sqlSupportsDefaultValues(self):
    """Return whether SQL default values are supported.

    Subclasses must override to return True or False, indicating their
    SQL variant supports DEFAULT <value> in the CREATE statement.
    Subclass responsibility.

    """
    raise AbstractError


class ModelObject:
  pass


class Model:

  def writeCreateSQL(self, generator, dirname):
    """Write SQL create statements.

    Creates the directory if necessary, sets the klasses' generator, and
    tells klasses to writeCreateSQL().

    """
    if not os.path.exists(dirname):
      os.mkdir(dirname)
    assert os.path.isdir(dirname)
    self._klasses.setSQLGenerator(generator)
    self._klasses.writeCreateSQL(generator, os.path.join(dirname, 'Create.sql'))

  def sqlDatabaseName(self):
    """Return the name of the database.

    This is either the 'Database' setting or self.name().

    """
    name = self.setting('Database', None)
    if name is None:
      name = self.name()
    return name

  def writeConnectToDatabase(self, generator, output, databasename):
    output.write('use %s;\n\n' % databasename)

  def writeInsertSamplesSQL(self, generator, dirname):
    if self._filename is not None:
      file = open(os.path.join(dirname, 'InsertSamples.sql'), 'w')
      self.writeConnectToDatabase(generator, file, self.sqlDatabaseName())

      if self.setting('DoNotSortSQLCreateStatementsByDependency', False):
        allKlasses = self.allKlassesInOrder()
      else:
        allKlasses = self.allKlassesInDependencyOrder()

      # delete the existing data
      wr = file.write
      if 0:
        # Woops. Our only auxiliary table is _MKClassIds, which we
        # *don't* want to delete. In the future we will likely
        # have other aux tables for lists and relationships. When
        # that happens, we'll need more granularity regarding
        # aux tables.
        names = self.auxiliaryTableNames()[:]
        names.reverse()
        for tableName in names:
          wr('delete from %s;\n' % tableName)
      reverseKlasses = allKlasses[:]
      reverseKlasses.reverse()
      for klass in reverseKlasses:
        if not klass.isAbstract():
          wr('delete from %s;\n' % klass.sqlTableName())
      wr('\n')

      self._klassSamples = {} # keyed by klass,
      # value is list of SQL strings (comments or INSERT statements)

      filenames = glob(os.path.join(self._filename, 'Sample*.csv'))
      for filename in filenames:
        lines = open(filename).readlines()
        try:
          self.writeInsertSamplesSQLForLines(lines, generator, file, filename)
        except SampleError, s:
          s.write(filename)
          sys.exit(1)

      # at this point the klassSamples dict has the collected samples for each klass
      # write the samples file
      for klass in allKlasses:
        samples = self._klassSamples.get(klass)
        if samples is not None:
          for line in samples:
            file.write(line)
        self.writePostKlassSamplesSQL(generator, file)

      self.writePostSamplesSQL(generator, file)
      file.close()

      del self._klassSamples

  def writePostKlassSamplesSQL(self, generator, file):
    pass

  def writeInsertSamplesSQLForLines(self, lines, generator, file, filename):
    readColumns = True
    parse = CSVParser.CSVParser().parse
    linenum = 0
    klass = None
    attrs = []
    try:
      for line in lines:
        linenum += 1
        try:
          fields = parse(line)
        except CSVParser.ParseError, err:
          raise SampleError(linenum, 'Syntax error: %s' % err)
        if fields is None:  # parser got embedded newline; continue with next line
          continue

        try:
          if self.areFieldsBlank(fields):
            pass # skip blank lines
          elif fields[0] and str(fields[0])[0] == '#':
            pass
          elif fields[0].lower().endswith(' objects'):
            klassName = fields[0].split()[0]
            try:
              klass = self.klass(klassName)
            except KeyError:
              raise SampleError(linenum,
                "Class '%s' is not defined" % klassName)
            samples = self._klassSamples.get(klass, None)
            if samples is None:
              samples = self._klassSamples[klass] = []
              samples.append('\n\n/* %s */\n\n' % klass.name())
            tableName = klass.sqlTableName()
            # print '>> table:', tableName
            readColumns = True
            for attr in attrs:
              attr.refByAttrName = None
            attrs = []
          elif readColumns:
            if klass is None:
              raise SampleError(linenum,
                "Have not yet seen an 'objects' declaration.")
            names = [name for name in fields if name]
            for name in names:
              if name == klass.sqlSerialColumnName():
                attrs.append(PrimaryKey(name, klass))
              else:
                # support "foo by bar"
                name = name.strip()
                parts = name.split(' ')
                if len(parts) == 1:
                  refByAttrName = None
                else:
                  parts = [p.strip() for p in parts]
                  if len(parts) != 3 \
                      or parts[1].lower() != 'by' \
                      or len(parts[2]) == 0:
                    raise SampleError(linenum,
                      "Attribute '%s' of class '%s'"
                      " is not in format 'foo' or 'foo-by-bar'"
                      % (name, klass.name()))
                  name = parts[0]
                  refByAttrName = parts[2]
                  # print '>> refByAttrName:', name, refByAttrName
                # locate the attr definiton
                try:
                  attr = klass.lookupAttr(name)
                  attrs.append(attr)
                except KeyError:
                  raise SampleError(linenum,
                    "Class '%s' has no attribute '%s'"
                    % (klass.name(), name))
                # error checking for "foo by bar" and set refByAttre
                if refByAttrName:
                  from MiddleKit.Core.ObjRefAttr import 
                    import ObjRefAttr as ObjRefAttrClass
                  if not isinstance(attr, ObjRefAttrClass):
                    raise SampleError(linenum,
                      "Cannot use 'by' feature with non-obj ref attributes."
                      " Attr %r of class %r is a %r."
                      % (name, klass.name(), attr.__class__.__name__))
                  try:
                    refByAttr = attr.targetKlass().lookupAttr(refByAttrName)
                  except KeyError:
                    raise SampleError(linenum,
                      "Attribute %r of class %r has a 'by' of %r,"
                      " but no such attribute can be found in target class %r."
                      % (name, klass.name(),
                        refByAttrName, attr.targetKlass().name()))
                  attr.refByAttr = refByAttr
                else:
                  attr.refByAttr = None
              # @@ 2000-10-29 ce: check that each attr.hasSQLColumn()
              for attr in attrs:
                assert not attr.get('isDerived', False)
              colNames = [attr.sqlName() for attr in attrs]
              # print '>> cols:', columns
              colSql = ','.join(colNames)
              readColumns = False
          else:
            if klass is None:
              raise SampleError(linenum,
                "Have not yet seen an 'objects' declaration.")
            values = fields[:len(attrs)]
            preinsertSQL = []
            i = 0
            for attr in attrs:
              try:
                value = values[i]
              except IndexError:
                if i == 0:
                  # too early to accept nulls?
                  raise SampleError(linenum,
                    "Couldn't find value for attribute"
                    " '%s'\nattrs = %r\nvalues for line = %r"
                    % (attr.name(), [a.name() for a in attrs], values))
                else:
                  # assume blank
                  # (Excel sometimes doesn't include all the commas)
                  value = ''
              value = attr.sqlForSampleInput(value)
              if isinstance(value, types.TupleType):
                # sqlForSampleInput can return a 2 tuple: (presql, sqlValue)
                assert len(value) == 2
                preinsertSQL.append(value[0])
                value = value[1]
              assert value, 'sql value cannot be blank: %r' % value
              try:
                values[i] = value
              except IndexError:
                values.append(value)
              i += 1
            values = ', '.join(values)
            for stmt in preinsertSQL:
              #print '>>', stmt
              samples.append(stmt)
            stmt = 'insert into %s (%s) values (%s);\n' % (tableName, colSql, values)
            # print '>>', stmt
            samples.append(stmt)
        except Exception:
          print
          print 'Samples error:'
          try:
            print '%s:%s' % (filename, linenum)
            print line
          except Exception:
            pass
          print
          raise
    finally:
      for attr in attrs:
        attr.refByAttr = None

  def areFieldsBlank(self, fields):
    """Utility method for writeInsertSamplesSQLForLines()."""
    if len(fields) == 0:
      return True
    for field in fields:
      if field:
        return False
    return True

  def writePostSamplesSQL(self, generator, output):
    pass


class Klasses:

  def sqlGenerator(self):
    return generator

  def setSQLGenerator(self, generator):
    self._sqlGenerator = generator

  def auxiliaryTableNames(self):
    """Return a list of table names in addition to the tables that hold objects.

    One popular user of this method is dropTablesSQL().

    """
    return ['_MKClassIds']

  def writeKeyValue(self, out, key, value):
    """Used by willCreateWriteSQL()."""
    key = key.ljust(12)
    out.write('# %s = %s\n' % (key, value))

  def writeCreateSQL(self, generator, out):
    """Write the SQL to define the tables for a set of classes.

    The target can be a file or a filename.

    """
    if type(out) in StringTypes:
      out = open(out, 'w')
      close = True
    else:
      close = False
    self.willWriteCreateSQL(generator, out)
    self._writeCreateSQL(generator, out)
    self.didWriteCreateSQL(generator, out)
    if close:
      out.close()

  def willWriteCreateSQL(self, generator, out):
    # @@ 2001-02-04 ce: break up this method
    wr = out.write
    kv = self.writeKeyValue
    wr('/*\nStart of generated SQL.\n\n')
    kv(out, 'Date', asctime(localtime(time())))
    kv(out, 'Python ver', sys.version)
    kv(out, 'Op Sys', os.name)
    kv(out, 'Platform', sys.platform)
    kv(out, 'Cur dir', os.getcwd())
    kv(out, 'Num classes', len(self._klasses))
    wr('\nClasses:\n')
    for klass in self._model.allKlassesInOrder():
      wr('\t%s\n' % klass.name())
    wr('*/\n\n')

    sql = generator.setting('PreSQL', None)
    if sql:
      wr('/* PreSQL start */\n' + sql + '\n/* PreSQL end */\n\n')

    dbName = generator.sqlDatabaseName()
    drop = generator.setting('DropStatements')
    if drop == 'database':
      wr(self.dropDatabaseSQL(dbName))
      wr(self.createDatabaseSQL(dbName))
      wr(self.useDatabaseSQL(dbName))
    elif drop == 'tables':
      wr(self.useDatabaseSQL(dbName))
      wr(self.dropTablesSQL())
    else:
      raise Exception, 'Invalid value for DropStatements setting: %r' % drop

  def dropDatabaseSQL(self, dbName):
    """Return SQL code that will remove the database with the given name.

    Used by willWriteCreateSQL().
    Subclass responsibility.

    """
    raise AbstractError, self.__class__

  def dropTablesSQL(self):
    """Return SQL code that will remove each of the tables in the database.

    Used by willWriteCreateSQL().
    Subclass responsibility.

    """
    raise AbstractError, self.__class__

  def createDatabaseSQL(self, dbName):
    """Return SQL code that will create the database with the given name.

    Used by willWriteCreateSQL().
    Subclass responsibility.

    """
    raise AbstractError, self.__class__

  def useDatabaseSQL(self, dbName):
    """Return SQL code that will use the database with the given name.

    Used by willWriteCreateSQL().
    Subclass responsibility.

    """
    raise AbstractError, self.__class__

  def _writeCreateSQL(self, generator, out):
    # assign the class ids up-front, so that we can resolve forward object references
    self.assignClassIds(generator)
    self.writeClassIdsSQL(generator, out)

    if self._model.setting('DoNotSortSQLCreateStatementsByDependency', False):
      # Generates the CREATE TABLEs in the order the classes were declared
      # but if you're not careful, than foreign keys will cause "unknown table" errors
      allKlasses = self._model.allKlassesInOrder()
    else:
      allKlasses = self._model.allKlassesInDependencyOrder()

    for klass in allKlasses:
      klass.writeCreateSQL(self._sqlGenerator, out)

  def writeClassIdsSQL(self, generator, out):
    wr = out.write
    wr('''\
create table _MKClassIds (
  id int not null primary key,
  name varchar(100)
);
''')
    for klass in self._model._allKlassesInOrder:
      wr('insert into _MKClassIds (id, name) values ')
      wr("\t(%s, '%s');\n" % (klass.id(), klass.name()))
    wr('\n')

  def listTablesSQL(self):
    # return a SQL command to list all tables in the database
    # this is database-specific, so by default we return nothing
    return ''

  def didWriteCreateSQL(self, generator, out):
    sql = generator.setting('PostSQL', None)
    if sql:
      out.write('/* PostSQL start */\n' + sql + '\n/* PostSQL end */\n\n')
    out.write(self.listTablesSQL())
    out.write('/* end of generated SQL */\n')


import KlassSQLSerialColumnName


class Klass:

  def writeCreateSQL(self, generator, out):
    for attr in self.attrs():
      attr.writeAuxiliaryCreateTable(generator, out)
    if not self.isAbstract():
      self.writeCreateTable(generator, out)
      self.writePostCreateTable(generator, out)

  def writeCreateTable(self, generator, out):
    name = self.name()
    wr = out.write
    wr('create table %s (\n' % self.sqlTableName())
    wr(self.primaryKeySQLDef(generator))
    if generator.model().setting('DeleteBehavior', 'delete') == 'mark':
      self.writeDeletedSQLDef(generator, out)
      wr(',\n')
    first = True
    sqlAttrs = []
    nonSQLAttrs = []
    for attr in self.allAttrs():
      attr.containingKlass = self # as opposed to the declaring klass of the attr
      if attr.hasSQLColumn():
        sqlAttrs.append(attr)
      else:
        nonSQLAttrs.append(attr)
    for attr in sqlAttrs:
      if first:
        first = False
      else:
        wr(',\n')
      attr.writeCreateSQL(generator, out)
    self.writeIndexSQLDefsInTable(wr)
    for attr in nonSQLAttrs:
      attr.writeCreateSQL(generator, out)
      wr('\n')
    wr(');\n')
    self.writeIndexSQLDefsAfterTable(wr)
    wr('\n\n')
    # cleanup
    for attr in self.allAttrs():
      attr.containingKlass = None

  def writePostCreateTable(self, generator, out):
    pass

  def primaryKeySQLDef(self, generator):
    """Return SQL for primary key.

    Returns a one-liner that becomes part of the CREATE statement for
    creating the primary key of the table. SQL generators often override
    this mix-in method to customize the creation of the primary key for
    their SQL variant. This method should use self.sqlSerialColumnName()
    and often ljust()s it by self.maxNameWidth().

    """
    return '    %s int not null primary key,\n' \
      % self.sqlSerialColumnName().ljust(self.maxNameWidth())

  def writeDeletedSQLDef(self, generator, out):
    """Return SQL for deleted timestamp.

    Returns a the column definition that becomes part of the CREATE
    statement for the deleted timestamp field of the table.
    This is used if DeleteBehavior is set to "mark".

    """
    row = {'Attribute': 'deleted', 'Type': 'DateTime'}
    # create a "DateTimeAttr", so that the correct database type is used
    # depending on the backend database.
    datetime = generator.model().coreClass('DateTimeAttr')(row)
    datetime.setKlass(self)
    datetime.writeCreateSQL(generator, out)

  def maxNameWidth(self):
    return 30 # @@ 2000-09-15 ce: Ack! Duplicated from Attr class below

  def writeIndexSQLDefsInTable(self, wr):
    """Return SQL for creating indexes in table.

    Subclasses should override this or writeIndexSQLDefsAfterTable,
    or no indexes will be created.

    """
    pass

  def writeIndexSQLDefsAfterTable(self, wr):
    """"Return SQL for creating indexes after table.

    Subclasses should override this or writeIndexSQLDefsInTable,
    or no indexes will be created.

    """
    pass

  def sqlTableName(self):
    """Return table name.

    Can be overidden to allow for table names that do not conflict
    with SQL reserved words. dr 08-08-2002 - MSSQL uses [tablename]
    """
    return self.name()


class Attr:

  def sqlName(self):
    return self.name()

  def hasSQLColumn(self):
    """Return whether attribute corresponds to table column.

    Returns true if the attribute has a direct correlating SQL column
    in its class' SQL table definition. Most attributes do.
    Those of type list do not.

    """
    return not self.get('isDerived', False)

  def sqlForSampleInput(self, input):
    """Return SQL for sample input.

    Users of Attr should invoke this method, but subclasses and mixins
    should implement sqlForNonNoneSampleInput() instead.

    """
    input = input.strip()
    if input == '':
      input = self.get('Default', '')
    if input in (None, 'None', 'none'):
      return self.sqlForNone()
    else:
      s = self.sqlForNonNoneSampleInput(input)
      assert type(s) in StringTypes + (types.TupleType,), \
        '%r, %r, %r' % (s, type(s), self)
      return s

  def sqlForNone(self):
    return 'NULL'

  def sqlForNonNoneSampleInput(self, input):
    return input

  def writeCreateSQL(self, generator, out):
    """Write SQL create command.

    The klass argument is the containing klass of the attribute
    which can be different than the declaring klass.

    """
    try:
      if self.hasSQLColumn():
        self.writeRealCreateSQLColumn(generator, out)
      else:
        out.write('\t/* %(Name)s %(Type)s - not a SQL column */' % self)
    except Exception:
      bar = '*'*78
      print
      print bar
      print 'exception for attribute:'
      print '%s.%s' % (self.klass().name(), self.name())
      print
      try:
        from pprint import pprint
        pprint(self.data)
      except Exception:
        pass
      print bar
      print
      raise

  def writeRealCreateSQLColumn(self, generator, out):
    name = self.sqlName().ljust(self.maxNameWidth())
    if self.isRequired():
      notNullSQL = ' not null'
    else:
      notNullSQL = self.sqlNullSpec()
    if generator.sqlSupportsDefaultValues():
      defaultSQL = self.createDefaultSQL()
      if defaultSQL:
        defaultSQL = ' ' + defaultSQL
    else:
      defaultSQL = ''
    out.write('\t%s %s%s%s%s' % (name, self.sqlTypeOrOverride(),
      self.uniqueSQL(), notNullSQL, defaultSQL))

  def writeAuxiliaryCreateTable(self, generator, out):
    # most attribute types have no such beast
    pass

  def sqlNullSpec(self):
    return ''

  def createDefaultSQL(self):
    default = self.get('SQLDefault', None)
    if default is None:
      default = self.get('Default', None)
      if default is not None:
        default = self.sqlForSampleInput(str(default))
    if default:
      default = str(default).strip()
      if default.lower() == 'none':  # kind of redundant
        default = None
      return 'default ' + default
    else:
      return ''

  def maxNameWidth(self):
    return 30 # @@ 2000-09-14 ce: should compute that from names rather than hard code

  def sqlTypeOrOverride(self):
    """Return SQL type.

    Returns the SQL type as specified by the attribute class, or
    the SQLType that the user can specify in the model to override that.
    For example, SQLType='image' for a string attribute.
    Subclasses should not override this method, but sqlType() instead.

    """
    return self.get('SQLType') or self.sqlType()

  def sqlType(self):
    raise AbstractError, self.__class__

  def sqlColumnName(self):
    """Return SQL column name.

    Returns the SQL column name corresponding to this attribute
    which simply defaults to the attribute's name. Subclasses may
    override to customize.

    """
    if not self._sqlColumnName:
      self._sqlColumnName = self.name()
    return self._sqlColumnName

  def uniqueSQL(self):
    """Return SQL to use within a column definition to make it unique."""
    return self.boolForKey('isUnique') and ' unique' or ''


class BoolAttr:

  def sqlType(self):
    # @@ 2001-02-04 ce: is this ANSI SQL? or at least common SQL?
    return 'bool'

  def sqlForNonNoneSampleInput(self, input):
    try:
      input = input.upper()
    except Exception:
      pass
    if input in (False, 'FALSE', 'NO', '0', '0.0', 0, 0.0):
      value = 0
    elif input in (True, 'TRUE', 'YES', '1', '1.0', 1, 1.0):
      value = 1
    else:
      raise ValueError, "invalid bool input: %r" % input
    assert value in (0, 1), value
    return str(value)


class IntAttr:

  def sqlType(self):
    return 'int'

  def sqlForNonNoneSampleInput(self, input):
    if not isinstance(input, types.IntType):
      value = str(input)
      if value.endswith('.0'):
        # numeric values from Excel-based models are always float
        value = value[:-2]
      try:
        int(value) # raises exception if value is invalid
      except ValueError, e:
        raise ValueError, str(e)+'. attr is '+self.name()
      return str(value)


class LongAttr:

  def sqlType(self):
    # @@ 2000-10-18 ce: is this ANSI SQL?
    return 'bigint'

  def sqlForNonNoneSampleInput(self, input):
    long(input) # raises exception if value is invalid
    return str(input)


class FloatAttr:

  def sqlType(self):
    return 'double precision'

  def sqlForNonNoneSampleInput(self, input):
    float(input) # raises exception if value is invalid
    return str(input)


class DecimalAttr:

  def sqlType(self):
    # the keys 'Precision' and 'Scale' are used because all the
    # SQL docs I read say:  decimal(precision, scale)
    precision = self.get('Precision', None)
    if precision is None:
      # the following setting is for backwards compatibility
      if self.klass().klasses()._model.setting('UseMaxForDecimalPrecision', False):
        precision = self.get('Max', None)
        if not precision:
          precision = None
      if precision is None:
        precision = 11
    scale = self.get('Scale', None)
    if scale is None:
      scale = self.get('numDecimalPlaces', 3)
    return 'decimal(%s,%s)' % (precision, scale)

  def sqlForNonNoneSampleInput(self, input):
    return str(input)


class StringAttr:

  def sqlType(self):
    """Return SQL type.

    Subclass responsibility.
    Subclasses should take care that if self['Max'] == self['Min']
    then the "char" type is preferred over "varchar".
    Also, most (if not all) SQL databases require different types
    depending on the length of the string.

    """
    raise AbstractError, self.__class__

  def sqlForNonNoneSampleInput(self, input):
    value = input
    if value == "''":
      value = ''
    elif value.find('\\') != -1:
      if 1:
        # add spaces before and after, to prevent
        # syntax error if value begins or ends with "
        value = eval('""" '+str(value)+' """')
        value = repr(value[1:-1]) # trim off the spaces
        value = value.replace('\\011', '\\t')
        value = value.replace('\\012', '\\n')
        return value
    value = repr(value)
    #print '>> value:', value
    return value


class AnyDateTimeAttr:

  def sqlType(self):
    return self['Type'] # e.g., date, time and datetime

  def sqlForNonNoneSampleInput(self, input):
    return repr(input)


class ObjRefAttr:

  def sqlName(self):
    if self.setting('UseBigIntObjRefColumns', False):
      return self.name() + 'Id'  # old way: one 64 bit column
    else:
      # new way: 2 int columns for class id and obj id
      name = self.name()
      classIdName, objIdName = self.setting('ObjRefSuffixes')
      classIdName = name + classIdName
      objIdName = name + objIdName
      return '%s,%s' % (classIdName, objIdName)

  def writeRealCreateSQLColumn(self, generator, out):
    if self.setting('UseBigIntObjRefColumns', False):
      # the old technique of having both the class id and the obj id in one 64 bit reference
      name = self.sqlName().ljust(self.maxNameWidth())
      if self.get('Ref', None):
        refs = ' references %(Type)s(%(Type)sId)' % self
      else:
        refs = ''
      if self.isRequired():
        notNull = ' not null'
      else:
        notNull = self.sqlNullSpec()
      out.write('\t%s %s%s%s' % (name, self.sqlTypeOrOverride(), refs, notNull))
    else:
      # the new technique uses one column for each part of the obj ref: class id and obj id
      classIdName = self.name()+self.setting('ObjRefSuffixes')[0]
      classIdName = classIdName.ljust(self.maxNameWidth())
      objIdName = self.name()+self.setting('ObjRefSuffixes')[1]
      objIdName = objIdName.ljust(self.maxNameWidth())
      if self.isRequired():
        notNull = ' not null'
      else:
        notNull = self.sqlNullSpec()
      classIdDefault = ' default %s' % self.targetKlass().id()
      # ^ this makes the table a little to easier to work with in some cases
      # (you can often just insert the obj id)
      objIdRef = ''
      if self.get('Ref', None) or (
          self.setting('GenerateSQLReferencesForObjRefsToSingleClasses', False)
            and len(self.targetKlass().subklasses()) == 0):
        if self.get('Ref', None) not in ('0', 0, 0.0, False):
          objIdRef = self.objIdReferences()
      out.write('\t%s %s%s%s%s, /* %s */ \n' % (
        classIdName, self.sqlTypeOrOverride(), notNull, classIdDefault,
          self.classIdReferences(), self.targetClassName()))
      out.write('\t%s %s%s%s' % (objIdName, self.sqlTypeOrOverride(),
        notNull, objIdRef))

  def classIdReferences(self):
    return ' references _MKClassIds'

  def objIdReferences(self):
    targetKlass = self.targetKlass()
    return ' references %s(%s) ' % (
      targetKlass.sqlTableName(), targetKlass.sqlSerialColumnName())

  def sqlForNone(self):
    if self.setting('UseBigIntObjRefColumns', False):
      return 'NULL'
    else:
      return 'NULL,NULL'

  def sqlForNonNoneSampleInput(self, input):
    """Get SQL for non-None sample input.

    Obj ref sample data format is "Class.serialNum", such as "Thing.3".
    If the Class and period are missing, then the obj ref's type is assumed.

    Also, a comment can follow the value after a space:
    "User.3 Joe Schmoe" or "User.3 - Joe Schmoe"
    This is useful so that you can look at the sample later and know
    what the obj ref value is referring to without having to look it up.
    MiddleKit only looks at the first part ("User.3").

    """
    if self.refByAttr:
      # the column was spec'ed as "foo by bar".
      # so match by "bar" value, not serial number.
      # refByAttr holds the "bar" attr
      targetKlass = self.targetKlass()
      refByAttr = self.refByAttr
      assert targetKlass is refByAttr.klass()
      sql = '(select %s from %s where %s=%s)' % (
        targetKlass.sqlSerialColumnName(), targetKlass.sqlTableName(),
        refByAttr.sqlColumnName(), refByAttr.sqlForSampleInput(input))
      sql = str(targetKlass.id()) + ',' + sql
      # print '>> sql =', sql
      return sql
      # caveat: this only works if the object is found directly in the
      # target class. i.e., inheritance is not supported
      # caveat: this does not work if the UseBigIntObjRefColumns setting
      # is true (by default it is false)
      # caveat: MS SQL Server supports subselects but complains
      # "Subqueries are not allowed in this context. Only scalar expressions are allowed."
      # so more work is needed in its SQL generator
    else:
      # the de facto technique of <serialnum> or <class name>.<serial num>
      input = input.split()
      # this gets rid of the sample value comment described above
      if input:
        input = input[0]
      else:
        input = ''
      parts = input.split('.')
      if len(parts) == 2:
        className = parts[0]
        objSerialNum = parts[1]
      else:
        className = self.targetClassName()
        objSerialNum = input or 'null'
      klass = self.klass().klasses()._model.klass(className)
      klassId = klass.id()
      if self.setting('UseBigIntObjRefColumns', False):
        objRef = objRefJoin(klassId, objSerialNum)
        return str(objRef)
      else:
        return '%s,%s' % (klassId, objSerialNum)


class ListAttr:

  def sqlType(self):
    raise Exception, 'Lists do not have a SQL type.'

  def hasSQLColumn(self):
    return False

  def sqlForSampleInput(self, input):
    raise Exception, 'Lists are implicit. They cannot have sample values.'


class EnumAttr:

  def sqlType(self):
    if self.usesExternalSQLEnums():
      tableName, valueColName, nameColName = self.externalEnumsSQLNames()
      return 'int references %s(%s)' % (tableName, valueColName)
    else:
      return self.nativeEnumSQLType()

  def nativeEnumSQLType(self):
    maxLen = max([len(e) for e in self.enums()])
    return 'varchar(%s)' % maxLen

  def sqlForNonNoneSampleInput(self, input):
    if self.usesExternalSQLEnums():
      return str(self.intValueForString(input))
    else:
      assert input in self._enums, 'input=%r, enums=%r' % (input, self._enums)
      return repr(input)

  def writeAuxiliaryCreateTable(self, generator, out):
    if self.usesExternalSQLEnums():
      tableName, valueColName, nameColName = self.externalEnumsSQLNames()
      out.write('create table %s (\n' % tableName)
      out.write('\t%s int not null primary key,\n' % valueColName)
      out.write('\t%s varchar(255)\n' % nameColName)
      out.write(');\n')
      i = 0
      for enum in self.enums():
        out.write("insert into %(tableName)s values (%(i)i, '%(enum)s');\n" % locals())
        i += 1
      out.write('\n')


  ## Settings ##

  def usesExternalSQLEnums(self):
    flag = getattr(self, '_usesExternalSQLEnums', None)
    if flag is None:
      flag = self.model().usesExternalSQLEnums()
      self._usesExternalSQLEnums = flag
    return flag

  def externalEnumsSQLNames(self):
    """Return the tuple (tableName, valueColName, nameColName).

    This is derived from the model setting ExternalEnumsSQLNames.

    """
    names = getattr(self, '_externalEnumsSQLNames', None)
    if names is None:
      _ClassName = self.klass().name()
      ClassName = _ClassName[0].upper() + _ClassName[1:]
      className = _ClassName[0].lower() + _ClassName[1:]
      _AttrName = self.name()
      AttrName = _AttrName[0].upper() + _AttrName[1:]
      attrName = _AttrName[0].lower() + _AttrName[1:]
      values = locals()
      names = self.setting('ExternalEnumsSQLNames')
      names = [names['TableName'], names['ValueColName'], names['NameColName']]
      for i in range(len(names)):
        names[i] %= values
      self._externalEnumsSQLNames = names
    return names


class PrimaryKey:
  """Help class for dealing with primary keys.

  This class is not a 'standard' attribute, but just a helper class for the
  writeInsertSamplesSQLForLines method, in case the samples.csv file contains
  a primary key column (i.e. the serial numbers are specified explicitly).

  """

  def __init__(self, name, klass):
    self._name = name
    self._klassid = klass.id()
    self._props = {'isDerived': False}

    # this is for PostgreSQLSQLGenerator, but it's awkward to keep it there
    self._klass = klass
    if not hasattr(klass, '_maxSerialNum'):
      klass._maxSerialNum = 0

  def name(self):
    return self._name

  def sqlName(self):
    return self.name()

  def get(self, key, default=0):
    return self._props.get(key, default)

  def sqlForSampleInput(self, input):
    return input
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