Python expressions.Ref方法代碼示例

# 需要導入模塊: from django.db.models import expressions [as 別名]
# 或者: from django.db.models.expressions import Ref [as 別名]
def resolve_ref(self, name, allow_joins=True, reuse=None, summarize=False):
        if not allow_joins and LOOKUP_SEP in name:
            raise FieldError("Joined field references are not permitted in this query")
        if name in self.annotations:
            if summarize:
                # Summarize currently means we are doing an aggregate() query
                # which is executed as a wrapped subquery if any of the
                # aggregate() elements reference an existing annotation. In
                # that case we need to return a Ref to the subquery's annotation.
                return Ref(name, self.annotation_select[name])
            else:
                return self.annotation_select[name]
        else:
            field_list = name.split(LOOKUP_SEP)
            field, sources, opts, join_list, path = self.setup_joins(
                field_list, self.get_meta(),
                self.get_initial_alias(), reuse)
            targets, _, join_list = self.trim_joins(sources, join_list, path)
            if len(targets) > 1:
                raise FieldError("Referencing multicolumn fields with F() objects "
                                 "isn't supported")
            if reuse is not None:
                reuse.update(join_list)
            col = targets[0].get_col(join_list[-1], sources[0])
            return col 

# 需要導入模塊: from django.db.models import expressions [as 別名]
# 或者: from django.db.models.expressions import Ref [as 別名]
def resolve_ref(self, name, allow_joins=True, reuse=None, summarize=False):
        if not allow_joins and LOOKUP_SEP in name:
            raise FieldError("Joined field references are not permitted in this query")
        if name in self.annotations:
            if summarize:
                # Summarize currently means we are doing an aggregate() query
                # which is executed as a wrapped subquery if any of the
                # aggregate() elements reference an existing annotation. In
                # that case we need to return a Ref to the subquery's annotation.
                return Ref(name, self.annotation_select[name])
            else:
                return self.annotation_select[name]
        else:
            field_list = name.split(LOOKUP_SEP)
            join_info = self.setup_joins(field_list, self.get_meta(), self.get_initial_alias(), can_reuse=reuse)
            targets, _, join_list = self.trim_joins(join_info.targets, join_info.joins, join_info.path)
            if len(targets) > 1:
                raise FieldError("Referencing multicolumn fields with F() objects "
                                 "isn't supported")
            if reuse is not None:
                reuse.update(join_list)
            col = targets[0].get_col(join_list[-1], join_info.targets[0])
            return col 

# 需要導入模塊: from django.db.models import expressions [as 別名]
# 或者: from django.db.models.expressions import Ref [as 別名]
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 

# 需要導入模塊: from django.db.models import expressions [as 別名]
# 或者: from django.db.models.expressions import Ref [as 別名]
def resolve_ref(self, name, allow_joins=True, reuse=None, summarize=False):
        if not allow_joins and LOOKUP_SEP in name:
            raise FieldError("Joined field references are not permitted in this query")
        if name in self.annotations:
            if summarize:
                # Summarize currently means we are doing an aggregate() query
                # which is executed as a wrapped subquery if any of the
                # aggregate() elements reference an existing annotation. In
                # that case we need to return a Ref to the subquery's annotation.
                return Ref(name, self.annotation_select[name])
            else:
                return self.annotations[name]
        else:
            field_list = name.split(LOOKUP_SEP)
            join_info = self.setup_joins(field_list, self.get_meta(), self.get_initial_alias(), can_reuse=reuse)
            targets, final_alias, join_list = self.trim_joins(join_info.targets, join_info.joins, join_info.path)
            if len(targets) > 1:
                raise FieldError("Referencing multicolumn fields with F() objects "
                                 "isn't supported")
            # Verify that the last lookup in name is a field or a transform:
            # transform_function() raises FieldError if not.
            join_info.transform_function(targets[0], final_alias)
            if reuse is not None:
                reuse.update(join_list)
            col = targets[0].get_col(join_list[-1], join_info.targets[0])
            return col 

# 需要導入模塊: from django.db.models import expressions [as 別名]
# 或者: from django.db.models.expressions import Ref [as 別名]
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