# dokumentasi Django 2.0.8

# Kode sumber untuk django.contrib.postgres.indexes

    from django.db.models import Index

    __all__ = ['BrinIndex', 'GinIndex', 'GistIndex']

    class MaxLengthMixin:
        # Allow an index name longer than 30 characters since the suffix is 4
        # characters (usual limit is 3). Since this index can only be used on
        # PostgreSQL, the 30 character limit for cross-database compatibility isn't
        # applicable.
        max_name_length = 31

    class BrinIndex(MaxLengthMixin, Index):
        suffix = 'brin'

        def __init__(self, *, pages_per_range=None, **kwargs):
            if pages_per_range is not None and pages_per_range <= 0:
                raise ValueError('pages_per_range must be None or a positive integer')
            self.pages_per_range = pages_per_range
            super().__init__(**kwargs)

        def deconstruct(self):
            path, args, kwargs = super().deconstruct()
            if self.pages_per_range is not None:
                kwargs['pages_per_range'] = self.pages_per_range
            return path, args, kwargs

        def create_sql(self, model, schema_editor, using=''):
            statement = super().create_sql(model, schema_editor, using=' USING brin')
            if self.pages_per_range is not None:
                statement.parts['extra'] = ' WITH (pages_per_range={})'.format(
                    schema_editor.quote_value(self.pages_per_range)
                ) + statement.parts['extra']
            return statement

    class GinIndex(Index):
        suffix = 'gin'

        def __init__(self, *, fastupdate=None, gin_pending_list_limit=None, **kwargs):
            self.fastupdate = fastupdate
            self.gin_pending_list_limit = gin_pending_list_limit
            super().__init__(**kwargs)

        def deconstruct(self):
            path, args, kwargs = super().deconstruct()
            if self.fastupdate is not None:
                kwargs['fastupdate'] = self.fastupdate
            if self.gin_pending_list_limit is not None:
                kwargs['gin_pending_list_limit'] = self.gin_pending_list_limit
            return path, args, kwargs

        def create_sql(self, model, schema_editor, using=''):
            statement = super().create_sql(model, schema_editor, using=' USING gin')
            with_params = []
            if self.gin_pending_list_limit is not None:
                with_params.append('gin_pending_list_limit = %d' % self.gin_pending_list_limit)
            if self.fastupdate is not None:
                with_params.append('fastupdate = {}'.format('on' if self.fastupdate else 'off'))
            if with_params:
                statement.parts['extra'] = 'WITH ({}) {}'.format(', '.join(with_params), statement.parts['extra'])
            return statement

    class GistIndex(MaxLengthMixin, Index):
        suffix = 'gist'

        def __init__(self, *, buffering=None, fillfactor=None, **kwargs):
            self.buffering = buffering
            self.fillfactor = fillfactor
            super().__init__(**kwargs)

        def deconstruct(self):
            path, args, kwargs = super().deconstruct()
            if self.buffering is not None:
                kwargs['buffering'] = self.buffering
            if self.fillfactor is not None:
                kwargs['fillfactor'] = self.fillfactor
            return path, args, kwargs

        def create_sql(self, model, schema_editor):
            statement = super().create_sql(model, schema_editor, using=' USING gist')
            with_params = []
            if self.buffering is not None:
                with_params.append('buffering = {}'.format('on' if self.buffering else 'off'))
            if self.fillfactor is not None:
                with_params.append('fillfactor = %s' % self.fillfactor)
            if with_params:
                statement.parts['extra'] = 'WITH ({}) {}'.format(', '.join(with_params), statement.parts['extra'])
            return statement