def reduce_columns(columns, *clauses, **kw):
"""given a list of columns, return a 'reduced' set based on natural equivalents.
the set is reduced to the smallest list of columns which have no natural
equivalent present in the list. A "natural equivalent" means that two columns
will ultimately represent the same value because they are related by a foreign key.
\*clauses is an optional list of join clauses which will be traversed
to further identify columns that are "equivalent".
\**kw may specify 'ignore_nonexistent_tables' to ignore foreign keys
whose tables are not yet configured.
This function is primarily used to determine the most minimal "primary key"
from a selectable, by reducing the set of primary key columns present
in the the selectable to just those that are not repeated.
"""
ignore_nonexistent_tables = kw.pop('ignore_nonexistent_tables', False)
columns = util.ordered_column_set(columns)
omit = util.column_set()
for col in columns:
for fk in chain(*[c.foreign_keys for c in col.proxy_set]):
for c in columns:
if c is col:
continue
try:
fk_col = fk.column
except exc.NoReferencedTableError:
if ignore_nonexistent_tables:
continue
else:
raise
if fk_col.shares_lineage(c):
omit.add(col)
break
if clauses:
def visit_binary(binary):
if binary.operator == operators.eq:
cols = util.column_set(
chain(*[c.proxy_set for c in columns.difference(omit)]))
if binary.left in cols and binary.right in cols:
for c in columns:
if c.shares_lineage(binary.right):
omit.add(c)
break
for clause in clauses:
visitors.traverse(clause, {}, {'binary': visit_binary})
return expression.ColumnSet(columns.difference(omit))
def reduce_columns(columns, *clauses, **kw):
"""given a list of columns, return a 'reduced' set based on natural equivalents.
the set is reduced to the smallest list of columns which have no natural
equivalent present in the list. A "natural equivalent" means that two columns
will ultimately represent the same value because they are related by a foreign key.
\*clauses is an optional list of join clauses which will be traversed
to further identify columns that are "equivalent".
\**kw may specify 'ignore_nonexistent_tables' to ignore foreign keys
whose tables are not yet configured.
This function is primarily used to determine the most minimal "primary key"
from a selectable, by reducing the set of primary key columns present
in the the selectable to just those that are not repeated.
"""
ignore_nonexistent_tables = kw.pop("ignore_nonexistent_tables", False)
columns = util.ordered_column_set(columns)
omit = util.column_set()
for col in columns:
for fk in chain(*[c.foreign_keys for c in col.proxy_set]):
for c in columns:
if c is col:
continue
try:
fk_col = fk.column
except exc.NoReferencedTableError:
if ignore_nonexistent_tables:
continue
else:
raise
if fk_col.shares_lineage(c):
omit.add(col)
break
if clauses:
def visit_binary(binary):
if binary.operator == operators.eq:
cols = util.column_set(chain(*[c.proxy_set for c in columns.difference(omit)]))
if binary.left in cols and binary.right in cols:
for c in columns:
if c.shares_lineage(binary.right):
omit.add(c)
break
for clause in clauses:
visitors.traverse(clause, {}, {"binary": visit_binary})
return expression.ColumnSet(columns.difference(omit))
def _determine_local_remote_pairs(self):
if not self.local_remote_pairs:
if self.remote_side:
if self.direction is MANYTOONE:
self.local_remote_pairs = [
(r, l) for l, r in
criterion_as_pairs(self.primaryjoin, consider_as_referenced_keys=self.remote_side, any_operator=True)
]
else:
self.local_remote_pairs = criterion_as_pairs(self.primaryjoin, consider_as_foreign_keys=self.remote_side, any_operator=True)
if not self.local_remote_pairs:
raise sa_exc.ArgumentError("Relation %s could not determine any local/remote column pairs from remote side argument %r" % (self, self.remote_side))
else:
if self.viewonly:
eq_pairs = self.synchronize_pairs
if self.secondaryjoin:
eq_pairs += self.secondary_synchronize_pairs
else:
eq_pairs = criterion_as_pairs(self.primaryjoin, consider_as_foreign_keys=self._foreign_keys, any_operator=True)
if self.secondaryjoin:
eq_pairs += criterion_as_pairs(self.secondaryjoin, consider_as_foreign_keys=self._foreign_keys, any_operator=True)
eq_pairs = [(l, r) for l, r in eq_pairs if self._col_is_part_of_mappings(l) and self._col_is_part_of_mappings(r)]
if self.direction is MANYTOONE:
self.local_remote_pairs = [(r, l) for l, r in eq_pairs]
else:
self.local_remote_pairs = eq_pairs
elif self.remote_side:
raise sa_exc.ArgumentError("remote_side argument is redundant against more detailed _local_remote_side argument.")
for l, r in self.local_remote_pairs:
if self.direction is ONETOMANY and not self._col_is_part_of_mappings(l):
raise sa_exc.ArgumentError("Local column '%s' is not part of mapping %s. "
"Specify remote_side argument to indicate which column "
"lazy join condition should compare against." % (l, self.parent))
elif self.direction is MANYTOONE and not self._col_is_part_of_mappings(r):
raise sa_exc.ArgumentError("Remote column '%s' is not part of mapping %s. "
"Specify remote_side argument to indicate which column lazy "
"join condition should bind." % (r, self.mapper))
self.local_side, self.remote_side = [util.ordered_column_set(x) for x in zip(*list(self.local_remote_pairs))]
def _determine_local_remote_pairs(self):
if not self.local_remote_pairs:
if self.remote_side:
if self.direction is MANYTOONE:
self.local_remote_pairs = [
(r, l)
for l, r in criterion_as_pairs(
self.primaryjoin, consider_as_referenced_keys=self.remote_side, any_operator=True
)
]
else:
self.local_remote_pairs = criterion_as_pairs(
self.primaryjoin, consider_as_foreign_keys=self.remote_side, any_operator=True
)
if not self.local_remote_pairs:
raise sa_exc.ArgumentError(
"Relation %s could not determine any local/remote column pairs from remote side argument %r"
% (self, self.remote_side)
)
else:
if self.viewonly:
eq_pairs = self.synchronize_pairs
if self.secondaryjoin:
eq_pairs += self.secondary_synchronize_pairs
else:
eq_pairs = criterion_as_pairs(
self.primaryjoin, consider_as_foreign_keys=self._foreign_keys, any_operator=True
)
if self.secondaryjoin:
eq_pairs += criterion_as_pairs(
self.secondaryjoin, consider_as_foreign_keys=self._foreign_keys, any_operator=True
)
eq_pairs = [
(l, r)
for l, r in eq_pairs
if self._col_is_part_of_mappings(l) and self._col_is_part_of_mappings(r)
]
if self.direction is MANYTOONE:
self.local_remote_pairs = [(r, l) for l, r in eq_pairs]
else:
self.local_remote_pairs = eq_pairs
elif self.remote_side:
raise sa_exc.ArgumentError(
"remote_side argument is redundant against more detailed _local_remote_side argument."
)
for l, r in self.local_remote_pairs:
if self.direction is ONETOMANY and not self._col_is_part_of_mappings(l):
raise sa_exc.ArgumentError(
"Local column '%s' is not part of mapping %s. "
"Specify remote_side argument to indicate which column "
"lazy join condition should compare against." % (l, self.parent)
)
elif self.direction is MANYTOONE and not self._col_is_part_of_mappings(r):
raise sa_exc.ArgumentError(
"Remote column '%s' is not part of mapping %s. "
"Specify remote_side argument to indicate which column lazy "
"join condition should bind." % (r, self.mapper)
)
self.local_side, self.remote_side = [util.ordered_column_set(x) for x in zip(*list(self.local_remote_pairs))]