我们从Python开源项目中，提取了以下48个代码示例，用于说明如何使用django.db.models.expressions.Col()。
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
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
def cached_col(self): from django.db.models.expressions import Col return Col(self.model._meta.db_table, self)
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
def process_rhs(self, compiler, connection): if hasattr(self.rhs, '_as_sql'): # If rhs is some QuerySet, don't touch it return super(GISLookup, self).process_rhs(compiler, connection) 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 spatial fields.') elif isinstance(self.rhs, (list, tuple)): geom = self.rhs[0] # Check if a band index was passed in the query argument. if ((len(self.rhs) == 2 and not self.lookup_name == 'relate') or (len(self.rhs) == 3 and self.lookup_name == 'relate')): self.process_band_indices() elif len(self.rhs) > 2: raise ValueError('Tuple too long for lookup %s.' % self.lookup_name) elif isinstance(self.lhs, RasterBandTransform): self.process_band_indices(only_lhs=True) rhs, rhs_params = super(GISLookup, self).process_rhs(compiler, connection) rhs = connection.ops.get_geom_placeholder(self.lhs.output_field, geom, compiler) return rhs, rhs_params
def process_rhs(self, compiler, connection): if isinstance(self.rhs, Query): # If rhs is some Query, don't touch it. return super(GISLookup, self).process_rhs(compiler, connection) 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 spatial fields.') elif isinstance(self.rhs, (list, tuple)): geom = self.rhs[0] # Check if a band index was passed in the query argument. if ((len(self.rhs) == 2 and not self.lookup_name == 'relate') or (len(self.rhs) == 3 and self.lookup_name == 'relate')): self.process_band_indices() elif len(self.rhs) > 2: raise ValueError('Tuple too long for lookup %s.' % self.lookup_name) elif isinstance(self.lhs, RasterBandTransform): self.process_band_indices(only_lhs=True) rhs, rhs_params = super(GISLookup, self).process_rhs(compiler, connection) rhs = connection.ops.get_geom_placeholder(self.lhs.output_field, geom, compiler) return rhs, rhs_params
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
