Python expressions.Col方法代码示例

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def process_rhs(self, compiler, connection):
        rhs, rhs_params = super(GISLookup, self).process_rhs(compiler, connection)
        if hasattr(self.rhs, '_as_sql'):
            # If rhs is some QuerySet, don't touch it
            return rhs, rhs_params

        geom = self.rhs
        if isinstance(self.rhs, Col):
            # Make sure the F Expression destination field exists, and
            # set an `srid` attribute with the same as that of the
            # destination.
            geo_fld = self.rhs.output_field
            if not hasattr(geo_fld, 'srid'):
                raise ValueError('No geographic field found in expression.')
            self.rhs.srid = geo_fld.srid
        elif isinstance(self.rhs, Expression):
            raise ValueError('Complex expressions not supported for GeometryField')
        elif isinstance(self.rhs, (list, tuple)):
            geom = self.rhs[0]
        rhs = connection.ops.get_geom_placeholder(self.lhs.output_field, geom, compiler)
        return rhs, rhs_params 

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def get_db_converters(self, expression):
        converters = super().get_db_converters(expression)
        internal_type = expression.output_field.get_internal_type()
        if internal_type == 'DateTimeField':
            converters.append(self.convert_datetimefield_value)
        elif internal_type == 'DateField':
            converters.append(self.convert_datefield_value)
        elif internal_type == 'TimeField':
            converters.append(self.convert_timefield_value)
        # Converter for Col is added with Database.register_converter()
        # in base.py.
        elif internal_type == 'DecimalField' and not isinstance(expression, Col):
            converters.append(self.convert_decimalfield_value)
        elif internal_type == 'UUIDField':
            converters.append(self.convert_uuidfield_value)
        elif internal_type in ('NullBooleanField', 'BooleanField'):
            converters.append(self.convert_booleanfield_value)
        return converters 

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def rewrite_cols(self, annotation, col_cnt):
        # We must make sure the inner query has the referred columns in it.
        # If we are aggregating over an annotation, then Django uses Ref()
        # instances to note this. However, if we are annotating over a column
        # of a related model, then it might be that column isn't part of the
        # SELECT clause of the inner query, and we must manually make sure
        # the column is selected. An example case is:
        #    .aggregate(Sum('author__awards'))
        # Resolving this expression results in a join to author, but there
        # is no guarantee the awards column of author is in the select clause
        # of the query. Thus we must manually add the column to the inner
        # query.
        orig_exprs = annotation.get_source_expressions()
        new_exprs = []
        for expr in orig_exprs:
            if isinstance(expr, Ref):
                # Its already a Ref to subquery (see resolve_ref() for
                # details)
                new_exprs.append(expr)
            elif isinstance(expr, Col):
                # Reference to column. Make sure the referenced column
                # is selected.
                col_cnt += 1
                col_alias = '__col%d' % col_cnt
                self.annotations[col_alias] = expr
                self.append_annotation_mask([col_alias])
                new_exprs.append(Ref(col_alias, expr))
            else:
                # Some other expression not referencing database values
                # directly. Its subexpression might contain Cols.
                new_expr, col_cnt = self.rewrite_cols(expr, col_cnt)
                new_exprs.append(new_expr)
        annotation.set_source_expressions(new_exprs)
        return annotation, col_cnt 

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def get_col(self, alias, output_field=None):
        if output_field is None:
            output_field = self
        if alias != self.model._meta.db_table or output_field != self:
            from django.db.models.expressions import Col
            return Col(alias, self, output_field)
        else:
            return self.cached_col 

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def cached_col(self):
        from django.db.models.expressions import Col
        return Col(self.model._meta.db_table, self) 

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def process_lhs(self, qn, connection):
        if isinstance(self.lhs, Col):
            language = translation.get_language() or settings.LANGUAGE_CODE
            self.lhs = KeyTransform(language, self.lhs)
        return super().process_lhs(qn, connection) 

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def get_decimalfield_converter(self, expression):
        # SQLite stores only 15 significant digits. Digits coming from
        # float inaccuracy must be removed.
        create_decimal = decimal.Context(prec=15).create_decimal_from_float
        if isinstance(expression, Col):
            quantize_value = decimal.Decimal(1).scaleb(-expression.output_field.decimal_places)

            def converter(value, expression, connection):
                if value is not None:
                    return create_decimal(value).quantize(quantize_value, context=expression.output_field.context)
        else:
            def converter(value, expression, connection):
                if value is not None:
                    return create_decimal(value)
        return converter 

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def expression_mentioned_fields(exp):
    if isinstance(exp, expressions.Col):
        field = exp.output_field or exp.field  # TODO: which one makes sense to use here?
        if field and field.name:
            return [field.name]
    elif hasattr(exp, 'get_source_expressions'):
        child_fields = []
        for source in exp.get_source_expressions():
            child_fields.extend(expression_mentioned_fields(source))
        return child_fields
    else:
        raise NotImplementedError('Unexpected expression class %s=%s when looking up mentioned fields.' % (exp.__class__.__name__, exp)) 

# 需要导入模块: from django.db.models import expressions [as 别名]
# 或者: from django.db.models.expressions import Col [as 别名]
def rewrite_cols(self, annotation, col_cnt):
        # We must make sure the inner query has the referred columns in it.
        # If we are aggregating over an annotation, then Django uses Ref()
        # instances to note this. However, if we are annotating over a column
        # of a related model, then it might be that column isn't part of the
        # SELECT clause of the inner query, and we must manually make sure
        # the column is selected. An example case is:
        #    .aggregate(Sum('author__awards'))
        # Resolving this expression results in a join to author, but there
        # is no guarantee the awards column of author is in the select clause
        # of the query. Thus we must manually add the column to the inner
        # query.
        orig_exprs = annotation.get_source_expressions()
        new_exprs = []
        for expr in orig_exprs:
            # FIXME: These conditions are fairly arbitrary. Identify a better
            # method of having expressions decide which code path they should
            # take.
            if isinstance(expr, Ref):
                # Its already a Ref to subquery (see resolve_ref() for
                # details)
                new_exprs.append(expr)
            elif isinstance(expr, (WhereNode, Lookup)):
                # Decompose the subexpressions further. The code here is
                # copied from the else clause, but this condition must appear
                # before the contains_aggregate/is_summary condition below.
                new_expr, col_cnt = self.rewrite_cols(expr, col_cnt)
                new_exprs.append(new_expr)
            elif isinstance(expr, Col) or (expr.contains_aggregate and not expr.is_summary):
                # Reference to column. Make sure the referenced column
                # is selected.
                col_cnt += 1
                col_alias = '__col%d' % col_cnt
                self.annotations[col_alias] = expr
                self.append_annotation_mask([col_alias])
                new_exprs.append(Ref(col_alias, expr))
            else:
                # Some other expression not referencing database values
                # directly. Its subexpression might contain Cols.
                new_expr, col_cnt = self.rewrite_cols(expr, col_cnt)
                new_exprs.append(new_expr)
        annotation.set_source_expressions(new_exprs)
        return annotation, col_cnt