class Select(RelExpr):
def __init__(self, cond, input):
assert isinstance(cond, ValExpr)
assert isinstance(input, RelExpr)
super(Select, self).__init__([input])
self.cond = cond
def __str__(self):
return literal(sym.SELECT) + literal(sym.ARG_L) + str(self.cond) + literal(sym.ARG_R) +\
' ' + str(paren(self.inputs[0]))
def validateSubtree(self, context: StatementContext):
self.inputs[0].validateSubtree(context)
self.cond.validateSubtree(context, self)
if self.cond.type != ValType.BOOLEAN:
raise self.validationError('selection condition {} has type {}; boolean expected'\
.format(self.cond, self.cond.type.value))
self.type = RelType(context.new_tmp(), self.inputs[0].type.attrs)
def info(self):
yield '{} => {}'.format(symbolic(sym.SELECT), self.type)
yield '|' + self.cond.info()
for i, line in enumerate(self.inputs[0].info()):
yield ('\\_' if i == 0 else ' ') + line
def sql(self):
for block in self.inputs[0].sql():
yield block
yield '{}({}) AS (SELECT * FROM {} WHERE {})'\
.format(self.type.sql_rel(), ', '.join(self.type.sql_attrs()),
self.inputs[0].type.sql_rel(),
self.cond.sql(self))
class Cross(RelExpr):
def __init__(self, left, right):
assert isinstance(left, RelExpr)
assert isinstance(right, RelExpr)
super(Cross, self).__init__([left, right])
def __str__(self):
return '{} {} {}'.format(paren(self.inputs[0]), literal(sym.CROSS), paren(self.inputs[1]))
def validateSubtree(self, context: StatementContext):
self.inputs[0].validateSubtree(context)
self.inputs[1].validateSubtree(context)
for a0, a1 in itertools.product(self.inputs[0].type.attrs, self.inputs[1].type.attrs):
if a0.can_be_confused_with(a1):
logger.warning('{}: attributes {} from the left input and {} from the right'
' become confused in the cross product output'\
.format(self, a0.str_ref_only(), a1.str_ref_only()))
self.type = RelType(context.new_tmp(),
self.inputs[0].type.attrs + self.inputs[1].type.attrs)
def info(self):
yield '{} => {}'.format(symbolic(sym.CROSS), self.type)
for i, line in enumerate(self.inputs[0].info()):
yield ('\\_' if i == 0 else '| ') + line
for i, line in enumerate(self.inputs[1].info()):
yield ('\\_' if i == 0 else ' ') + line
def sql(self):
for block in self.inputs[0].sql():
yield block
for block in self.inputs[1].sql():
yield block
yield '{}({}) AS (SELECT * FROM {}, {})'\
.format(self.type.sql_rel(), ', '.join(self.type.sql_attrs()),
self.inputs[0].type.sql_rel(), self.inputs[1].type.sql_rel())
class Project(RelExpr):
def __init__(self, attrs, input):
assert isinstance(attrs, list)
assert all(isinstance(attr, ValExpr) for attr in attrs)
assert isinstance(input, RelExpr)
super(Project, self).__init__([input])
self.attrs = attrs
def __str__(self):
return literal(sym.PROJECT) + literal(sym.ARG_L) +\
', '.join(str(attr) for attr in self.attrs) +\
literal(sym.ARG_R) + ' ' + str(paren(self.inputs[0]))
def validateSubtree(self, context: StatementContext):
self.inputs[0].validateSubtree(context)
output_attrspecs = list()
for attr in self.attrs:
attr.validateSubtree(context, self)
if isinstance(attr, AttrRef):
_, aidx = attr.internal_ref
output_attrspecs.append(self.inputs[0].type.attrs[aidx])
else:
output_attrspecs.append(AttrSpec(None, None, attr.type))
self.type = RelType(context.new_tmp(), output_attrspecs)
def info(self):
yield '{} => {}'.format(symbolic(sym.PROJECT), self.type)
for attr in self.attrs:
yield '|' + attr.info()
for i, line in enumerate(self.inputs[0].info()):
yield ('\\_' if i == 0 else ' ') + line
def sql(self):
for block in self.inputs[0].sql():
yield block
yield '{}({}) AS (SELECT DISTINCT {} FROM {})'\
.format(self.type.sql_rel(), ', '.join(self.type.sql_attrs()),
', '.join(attr.sql(self) for attr in self.attrs),
self.inputs[0].type.sql_rel())
class Aggr(RelExpr):
def __init__(self, groupbys, aggrs, input):
assert isinstance(groupbys, list)
assert all(isinstance(attr, ValExpr) for attr in groupbys)
assert isinstance(aggrs, list)
assert all(isinstance(attr, ValExpr) for attr in aggrs)
assert isinstance(input, RelExpr)
super(Aggr, self).__init__([input])
self.groupbys = groupbys
self.aggrs = aggrs
def __str__(self):
return literal(sym.AGGR) + literal(sym.ARG_L) +\
', '.join(str(attr) for attr in self.groupbys) +\
(': ' if len(self.groupbys) > 0 else '') +\
', '.join(str(attr) for attr in self.aggrs) +\
literal(sym.ARG_R) + ' ' + str(paren(self.inputs[0]))
def validateSubtree(self, context: StatementContext):
self.inputs[0].validateSubtree(context)
output_attrspecs = list()
for groupby in self.groupbys:
groupby.validateSubtree(context, self)
if isinstance(groupby, AttrRef):
_, aidx = groupby.internal_ref
output_attrspecs.append(self.inputs[0].type.attrs[aidx])
else:
output_attrspecs.append(AttrSpec(None, None, groupby.type))
for aggr in self.aggrs:
aggr.validateSubtree(context, self, allow_aggr=True)
aggr.checkSubtreeGroupInvariant(self)
if isinstance(aggr, AttrRef): # rare, but techincally possible
_, aidx = groupby.internal_ref
output_attrspecs.append(self.inputs[0].type.attrs[aidx])
else:
output_attrspecs.append(AttrSpec(None, None, aggr.type))
self.type = RelType(context.new_tmp(), output_attrspecs)
def info(self):
yield '{} => {}'.format(symbolic(sym.AGGR), self.type)
for groupby in self.groupbys:
yield '|group by: ' + groupby.info()
for aggr in self.aggrs:
yield '|' + aggr.info()
for i, line in enumerate(self.inputs[0].info()):
yield ('\\_' if i == 0 else ' ') + line
def sql(self):
for block in self.inputs[0].sql():
yield block
yield '{}({}) AS (SELECT {}{}{} FROM {}{}{})'\
.format(self.type.sql_rel(), ', '.join(self.type.sql_attrs()),
', '.join(attr.sql(self) for attr in self.groupbys),
(', ' if len(self.groupbys) > 0 else ''),
', '.join(attr.sql(self) for attr in self.aggrs),
self.inputs[0].type.sql_rel(),
(' GROUP BY ' if len(self.groupbys) > 0 else ''),
', '.join(attr.sql(self) for attr in self.groupbys))
class RelRef(RelExpr):
def __init__(self, rel):
super(RelRef, self).__init__()
assert isinstance(rel, str)
self.rel = rel
def __str__(self):
return self.rel
def validateSubtree(self, context: StatementContext):
# first check if this is a table in dbms:
if context.db.table_exists(self.rel):
attrspecs = [AttrSpec(self.rel, attr, type)\
for attr, type in context.db.describe(self.rel)]
self.type = RelType(context.new_tmp(), attrspecs)
self.view = None
return
# then check if this is a view defined in this session:
view_def = context.views.raw_def(self.rel)
if view_def is not None:
self.view = RelExpr.from_view_def(view_def)
self.view.validateSubtree(context)
attrspecs = [AttrSpec(self.rel, attrspec.name, attrspec.type)\
for attrspec in self.view.type.attrs]
self.type = RelType(self.view.type.tmp,
attrspecs) # don't create a new temp relation
return
# reference is not found:
raise self.validationError('relation {} does not exist'.format(
self.rel))
def info(self):
if self.view is None:
yield 'RELATION {} => {}'.format(self, self.type)
else:
yield 'VIEW {} => {}'.format(self, self.type)
for i, line in enumerate(self.view.info()):
yield ('\\_' if i == 0 else ' ') + line
def sql(self):
if self.view is None:
yield '{}({}) AS (SELECT * FROM {})'\
.format(self.type.sql_rel(), ', '.join(self.type.sql_attrs()), self.rel)
else:
for block in self.view.sql():
yield block
class SetOp(RelExpr):
def __init__(self, left, right):
assert isinstance(left, RelExpr)
assert isinstance(right, RelExpr)
super(SetOp, self).__init__([left, right])
def op(self):
if isinstance(self, Union):
return sym.UNION
elif isinstance(self, Diff):
return sym.DIFF
elif isinstance(self, Intersect):
return sym.INTERSECT
else:
assert False
def sql_op(self):
if isinstance(self, Union):
return 'UNION'
elif isinstance(self, Diff):
return 'EXCEPT'
elif isinstance(self, Intersect):
return 'INTERSECT'
else:
assert False
def __str__(self):
return '{} {} {}'.format(paren(self.inputs[0]), literal(self.op()),
paren(self.inputs[1]))
def validateSubtree(self, context: StatementContext):
self.inputs[0].validateSubtree(context)
self.inputs[1].validateSubtree(context)
if len(self.inputs[0].type.attrs) != len(self.inputs[1].type.attrs):
raise self.validationError(
'input relations to a set operation'
' do not have the same number of attributes')
for i, (a0, a1) in enumerate(
zip(self.inputs[0].type.attrs, self.inputs[1].type.attrs)):
if a0.type != a1.type:
raise self.validationError(
'input attributes at position {} have'
' different types: {} vs. {}'.format(i, a0, a1))
if a0.name != a1.name:
logger.warning('{}: input attributes at position {} have'
' different names: {} vs. {}'.format(
self, i, a0.str_ref_only(),
a1.str_ref_only()))
self.type = RelType(context.new_tmp(), self.inputs[0].type.attrs)
def info(self):
yield '{} => {}'.format(symbolic(self.op()), self.type)
for i, line in enumerate(self.inputs[0].info()):
yield ('\\_' if i == 0 else '| ') + line
for i, line in enumerate(self.inputs[1].info()):
yield ('\\_' if i == 0 else ' ') + line
def sql(self):
for block in self.inputs[0].sql():
yield block
for block in self.inputs[1].sql():
yield block
# interestingly, in the SQL below, parentheses around the two
# SELECT subqueries are not needed, and SQLite in fact would
# not like them:
yield '{}({}) AS (SELECT * FROM {} {} SELECT * FROM {})'\
.format(self.type.sql_rel(), ', '.join(self.type.sql_attrs()),
self.inputs[0].type.sql_rel(),
self.sql_op(),
self.inputs[1].type.sql_rel())
class Join(RelExpr):
def __init__(self, left, cond, right):
assert isinstance(left, RelExpr)
assert cond is None or isinstance(cond, ValExpr)
assert isinstance(right, RelExpr)
super(Join, self).__init__([left, right])
self.cond = cond
def __str__(self):
cond = '' if self.cond is None else\
literal(sym.ARG_L) + str(self.cond) + literal(sym.ARG_R)
return '{} {}{} {}'.format(paren(self.inputs[0]), literal(sym.JOIN),
cond, paren(self.inputs[1]))
def validateSubtree(self, context: StatementContext):
self.inputs[0].validateSubtree(context)
self.inputs[1].validateSubtree(context)
if self.cond is None:
self.pairs = list()
for i0, a0 in enumerate(self.inputs[0].type.attrs):
if a0.name is None:
continue
matches = [(i1, a1) for i1, a1 in enumerate(self.inputs[1].type.attrs)\
if a0.name == a1.name]
if len(matches) > 1:
raise self.validationError('ambiguity in natural join: {} from the left input'
' matches multiple attributes on the right'\
.format(a0.str_ref_only()))
elif len(matches) == 1:
i1, a1 = matches[0]
try:
context.check.function_call(symbolic(sym.EQ),
[a0.type, a1.type])
except TypeSysError as e:
raise self.validationError('natural join cannot equate {} and {}'\
.format(a0, a1))
self.pairs.append((i0, i1))
if len(self.pairs) == 0:
logger.warning(
'{}: no attributes with matching names found;'
' natural join degnerates into cross product'.format(self))
for i0, i1 in self.pairs:
if any((j0, j1) for j0, j1 in self.pairs
if j0 != i0 and j1 == i1):
raise self.validationError('ambiguity in natural join: {} from the right input'
' matches multiple attributes on the left'\
.format(self.inputs[1].type.attrs[i1]\
.str_ref_only()))
attrspecs = list()
for a0 in self.inputs[0].type.attrs:
attrspecs.append(a0)
for i1, a1 in enumerate(self.inputs[1].type.attrs):
if not any(i1 == i for _, i in self.pairs):
attrspecs.append(a1)
if any(
a1.can_be_confused_with(a0)
for a0 in self.inputs[0].type.attrs):
# this shouldn't happen under natural join rule, but oh well:
logger.warning('{}: attribute {} becomes confused with others'
' in the join output'\
.format(self, a1.str_ref_only()))
self.type = RelType(context.new_tmp(), attrspecs)
else:
self.cond.validateSubtree(context, self)
if self.cond.type != ValType.BOOLEAN:
raise self.validationError('join condition {} has type {}; boolean expected'\
.format(self.cond, self.cond.type.value))
for a0, a1 in itertools.product(self.inputs[0].type.attrs,
self.inputs[1].type.attrs):
if a0.can_be_confused_with(a1):
logger.warning('{}: attributes {} from the left input and {} from the right'
' become confused in the join output'\
.format(self, a0.str_ref_only(), a1.str_ref_only()))
self.type = RelType(
context.new_tmp(),
self.inputs[0].type.attrs + self.inputs[1].type.attrs)
def info(self):
yield '{} => {}'.format(symbolic(sym.JOIN), self.type)
if self.cond is not None:
yield '|' + self.cond.info()
elif len(self.pairs) == 0:
yield '|inferred: cross product with no join condition'
else:
for i0, i1 in self.pairs:
yield '|inferred: {}[0.{}] = {}[1.{}]'\
.format(self.inputs[0].type.attrs[i0].str_ref_only(), i0,
self.inputs[1].type.attrs[i1].str_ref_only(), i1)
for i, line in enumerate(self.inputs[0].info()):
yield ('\\_' if i == 0 else '| ') + line
for i, line in enumerate(self.inputs[1].info()):
yield ('\\_' if i == 0 else ' ') + line
def sql(self):
for block in self.inputs[0].sql():
yield block
for block in self.inputs[1].sql():
yield block
select = '*'
where = ''
if self.cond is None:
if len(self.pairs) > 0:
attrs = ['{}.{}'.format(self.inputs[0].type.sql_rel(), attr)\
for attr in self.inputs[0].type.sql_attrs()]
attrs += ['{}.{}'.format(self.inputs[1].type.sql_rel(), attr)\
for i, attr in enumerate(self.inputs[1].type.sql_attrs())\
if all(i != i1 for _, i1 in self.pairs)]
select = ', '.join(attrs)
eqs = ['{}.{} = {}.{}'.format(self.inputs[0].type.sql_rel(),
self.inputs[0].type.sql_attr(i0),
self.inputs[1].type.sql_rel(),
self.inputs[1].type.sql_attr(i1))\
for i0, i1 in self.pairs]
where = ' WHERE {}'.format(' AND '.join(eqs))
else:
where = ' WHERE {}'.format(self.cond.sql(self))
yield '{}({}) AS (SELECT {} FROM {}, {}{})'\
.format(self.type.sql_rel(), ', '.join(self.type.sql_attrs()),
select,
self.inputs[0].type.sql_rel(), self.inputs[1].type.sql_rel(),
where)
