def root_tables(self):
if util.all_of([self.left.op(), self.right.op()],
(Join, Projection)):
# Unraveling is not possible
return [self.left.op(), self.right.op()]
else:
return ir.distinct_roots(self.left, self.right)
def remap_overlapping_column_names(table_op, root_table, data_columns):
"""Return an ``OrderedDict`` mapping possibly suffixed column names to
column names without suffixes.
Parameters
----------
table_op : TableNode
The ``TableNode`` we're selecting from.
root_table : TableNode
The root table of the expression we're selecting from.
data_columns : set or frozenset
The available columns to select from
Returns
-------
mapping : OrderedDict[str, str]
A map from possibly-suffixed column names to column names without
suffixes.
"""
if not isinstance(table_op, ops.Join):
return None
left_root, right_root = ir.distinct_roots(table_op.left, table_op.right)
suffixes = {left_root: constants.LEFT_JOIN_SUFFIX,
right_root: constants.RIGHT_JOIN_SUFFIX}
column_names = [
({name, name + suffixes[root_table]} & data_columns, name)
for name in root_table.schema.names
]
mapping = OrderedDict(
(toolz.first(col_name), final_name)
for col_name, final_name in column_names if col_name
)
return mapping
def compute_projection_column_expr(expr, parent, data, scope=None, **kwargs):
result_name = getattr(expr, '_name', None)
op = expr.op()
parent_table_op = parent.table.op()
if isinstance(op, ir.TableColumn):
# slightly faster path for simple column selection
name = op.name
if name in data:
return data[name].rename(result_name or name)
if not isinstance(parent_table_op, ops.Join):
raise KeyError(name)
root_table, = op.root_tables()
left_root, right_root = ir.distinct_roots(
parent_table_op.left, parent_table_op.right
)
suffixes = {left_root: constants.LEFT_JOIN_SUFFIX,
right_root: constants.RIGHT_JOIN_SUFFIX}
return data.loc[:, name + suffixes[root_table]].rename(
result_name or name
)
data_columns = frozenset(data.columns)
additional_scope = {
t: map_new_column_names_to_data(
remap_overlapping_column_names(parent_table_op, t, data_columns),
data
) for t in op.root_tables()
}
new_scope = toolz.merge(scope, additional_scope)
result = execute(expr, new_scope, **kwargs)
assert result_name is not None, 'Column selection name is None'
return result.rename(result_name)
def root_tables(self):
cases, results, default = self.args
all_exprs = cases + results
if default is not None:
all_exprs.append(default)
return ir.distinct_roots(*all_exprs)
def root_tables(self):
if util.all_of([self.left.op(), self.right.op()], (Join, Projection)):
# Unraveling is not possible
return [self.left.op(), self.right.op()]
else:
return ir.distinct_roots(self.left, self.right)
def root_tables(self):
cases, results, default = self.args
all_exprs = cases + results
if default is not None:
all_exprs.append(default)
return ir.distinct_roots(*all_exprs)
