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from sqlglot import alias, exp
from sqlglot.errors import OptimizeError
from sqlglot.optimizer.scope import traverse_scope
def isolate_table_selects(expression):
for scope in traverse_scope(expression):
if len(scope.selected_sources) == 1:
continue
for (_, source) in scope.selected_sources.values():
if not isinstance(source, exp.Table):
continue
if not isinstance(source.parent, exp.Alias):
raise OptimizeError(
"Tables require an alias. Run qualify_tables optimization."
)
parent = source.parent
parent.replace(
exp.select("*")
.from_(
alias(source, source.name or parent.alias, table=True),
copy=False,
)
.subquery(parent.alias, copy=False)
)
return expression
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