def reduce_For(self, *kids):
r"%reduce FOR Identifier IN Set \
UNION OptionallyAliasedExpr \
OptFilterClause OptSortClause OptSelectLimit"
offset, limit = kids[8].val
if offset is not None or limit is not None:
subj = qlast.ForQuery(
iterator_alias=kids[1].val,
iterator=kids[3].val,
result=kids[5].val.expr,
result_alias=kids[5].val.alias,
where=kids[6].val,
orderby=kids[7].val,
implicit=True,
)
self.val = qlast.SelectQuery(
result=subj,
offset=offset,
limit=limit,
)
else:
self.val = qlast.ForQuery(
iterator_alias=kids[1].val,
iterator=kids[3].val,
result=kids[5].val.expr,
result_alias=kids[5].val.alias,
where=kids[6].val,
orderby=kids[7].val,
)
def reduce_For(self, *kids):
r"%reduce FOR Identifier IN Set \
UNION OptionallyAliasedExpr"
self.val = qlast.ForQuery(
iterator_alias=kids[1].val,
iterator=kids[3].val,
result=kids[5].val.expr,
result_alias=kids[5].val.alias,
)
def reduce_For(self, *kids):
r"%reduce FOR Identifier IN Set \
UNION OptionallyAliasedExpr \
OptFilterClause OptSortClause OptSelectLimit"
self.val = qlast.ForQuery(
iterator_alias=kids[1].val,
iterator=kids[3].val,
result=kids[5].val.expr,
result_alias=kids[5].val.alias,
where=kids[6].val,
orderby=kids[7].val,
offset=kids[8].val[0],
limit=kids[8].val[1],
)
def try_group_rewrite(
node: qlast.Query,
aliases: AliasGenerator,
) -> Optional[qlast.Query]:
"""
Try to apply some syntactic rewrites of GROUP expressions so we
can generate better code.
The two key desugarings are:
* Sink a shape into the internal group result
SELECT (GROUP ...) <shape>
[filter-clause] [order-clause] [other clauses]
=>
SELECT (
FOR GROUP ...
UNION <igroup-body> <shape>
[filter-clause]
[order-clause]
) [other clauses]
* Convert a FOR over a group into just an internal group (and
a trivial FOR)
FOR g in (GROUP ...) UNION <body>
=>
FOR GROUP ...
UNION (
FOR g IN (<group-body>)
UNION <body>
)
"""
# TODO: would Python's new pattern matching fit well here???
# Sink shapes into the GROUP
if (
isinstance(node, qlast.SelectQuery)
and isinstance(node.result, qlast.Shape)
and isinstance(node.result.expr, qlast.GroupQuery)
):
igroup = desugar_group(node.result.expr, aliases)
igroup = igroup.replace(result=qlast.Shape(
expr=igroup.result, elements=node.result.elements))
# FILTER gets sunk into the body of the FOR GROUP
if node.where or node.orderby:
igroup = igroup.replace(
# We need to move the result_alias in case
# the FILTER depends on it.
result_alias=node.result_alias,
where=node.where,
orderby=node.orderby,
)
return node.replace(
result=igroup, result_alias=None, where=None, orderby=None)
# Eliminate FORs over GROUPs
if (
isinstance(node, qlast.ForQuery)
and isinstance(node.iterator, qlast.GroupQuery)
):
igroup = desugar_group(node.iterator, aliases)
new_result = qlast.ForQuery(
iterator_alias=node.iterator_alias,
iterator=igroup.result,
result=node.result,
)
return igroup.replace(result=new_result, aliases=node.aliases)
return None
