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Merged
ravenac95 merged 1 commit into from
Oct 5, 2026
Merged

Walk every child field of expressions when building subquery scopes #11

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8 changes: 8 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,14 @@ The format is based on Keep a Changelog, and this project adheres to Semantic Ve

### Fixed

- `build_scope` now gives a subquery scope to a query in an expression field
the scope walk skipped: an aggregate's `FILTER (WHERE ...)`, `ORDER BY` and
`LIMIT`, a window frame bound, a `CAST` `FORMAT` or `DEFAULT` expression,
`IN UNNEST(...)`, and the other fields of those nodes it did not list. The
walk now takes the children of these nodes from the AST traversal instead of
a hand-written field list. As a result `walk_in_scope` and `find_all_in_scope`
also yield the nodes in those positions, such as columns in a `FILTER` clause
or window frame bound; the scope boundaries are unchanged.
- `build_scope` now gives a subquery scope to a query that is a bare operand of
an expression, such as the argument of `ARRAY(SELECT ...)`, instead of
leaving its tables and columns out of the scope tree. This matches sqlglot,
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181 changes: 55 additions & 126 deletions crates/polyglot-sql/src/scope.rs
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Expand Up @@ -1395,9 +1395,6 @@ impl<'a> WalkInScopeIter<'a> {
let mut children = Vec::new();

match expr {
Expression::Prepare(prepare) => {
children.push(&prepare.statement);
}
Expression::Select(select) => {
// Walk SELECT expressions
for e in &select.expressions {
Expand Down Expand Up @@ -1455,131 +1452,17 @@ impl<'a> WalkInScopeIter<'a> {
children.push(&offset.this);
}
}
Expression::And(bin)
| Expression::Or(bin)
| Expression::Add(bin)
| Expression::Sub(bin)
| Expression::Mul(bin)
| Expression::Div(bin)
| Expression::Mod(bin)
| Expression::Eq(bin)
| Expression::Neq(bin)
| Expression::Lt(bin)
| Expression::Lte(bin)
| Expression::Gt(bin)
| Expression::Gte(bin)
| Expression::BitwiseAnd(bin)
| Expression::BitwiseOr(bin)
| Expression::BitwiseXor(bin)
| Expression::Concat(bin) => {
children.push(&bin.left);
children.push(&bin.right);
}
Expression::Like(like) | Expression::ILike(like) => {
children.push(&like.left);
children.push(&like.right);
if let Some(escape) = &like.escape {
children.push(escape);
}
}
Expression::Not(un) | Expression::Neg(un) | Expression::BitwiseNot(un) => {
children.push(&un.this);
}
Expression::Function(func) => {
for arg in &func.args {
children.push(arg);
}
}
Expression::AggregateFunction(agg) => {
for arg in &agg.args {
children.push(arg);
}
}
Expression::WindowFunction(wf) => {
children.push(&wf.this);
for e in &wf.over.partition_by {
children.push(e);
}
for e in &wf.over.order_by {
children.push(&e.this);
}
}
Expression::Alias(alias) => {
children.push(&alias.this);
}
Expression::Case(case) => {
if let Some(operand) = &case.operand {
children.push(operand);
}
for (when_expr, then_expr) in &case.whens {
children.push(when_expr);
children.push(then_expr);
}
if let Some(else_clause) = &case.else_ {
children.push(else_clause);
}
}
Expression::Paren(paren) => {
children.push(&paren.this);
}
Expression::Ordered(ord) => {
children.push(&ord.this);
}
Expression::Table(_) | Expression::Subquery(_) | Expression::Exists(_) => {}
// The query operand gets its own scope, so it is not walked here.
Expression::In(in_expr) => {
children.push(&in_expr.this);
for e in &in_expr.expressions {
children.push(e);
}
// Note: in_expr.query creates a new scope - don't traverse
}
Expression::Between(between) => {
children.push(&between.this);
children.push(&between.low);
children.push(&between.high);
}
Expression::IsNull(is_null) => {
children.push(&is_null.this);
}
Expression::Cast(cast) => {
children.push(&cast.this);
}
Expression::Extract(extract) => {
children.push(&extract.this);
}
Expression::Coalesce(coalesce) => {
for e in &coalesce.expressions {
children.push(e);
}
}
Expression::NullIf(nullif) => {
children.push(&nullif.this);
children.push(&nullif.expression);
}
Expression::Table(_table) => {
// Tables don't have child expressions to traverse within scope
// (joins are handled at the Select level)
}
Expression::TryCatch(try_catch) => {
for stmt in &try_catch.try_body {
children.push(stmt);
}
if let Some(catch_body) = &try_catch.catch_body {
for stmt in catch_body {
children.push(stmt);
}
}
}
Expression::Column(_) | Expression::Literal(_) | Expression::Identifier(_) => {
// Leaf nodes - no children
}
// Subqueries and Exists create new scopes - don't traverse into them
Expression::Subquery(_) | Expression::Exists(_) => {}
_ => {
// Use the canonical AST traversal for other scalar expressions
// (typed functions, field access, filters, etc.). Scope
// boundaries are still enforced by should_stop_at.
children.extend(expr.children());
children.extend(expr.children().into_iter().filter(|child| {
!in_expr
.query
.as_ref()
.is_some_and(|query| std::ptr::eq(query, *child))
}));
}
_ => children.extend(expr.children()),
}

children
Expand Down Expand Up @@ -2108,6 +1991,52 @@ mod tests {
}
}

#[test]
fn test_subquery_in_expression_field_is_one_subquery_scope() {
use crate::DialectType::{BigQuery, Generic, Oracle, PostgreSQL};

for (dialect, sql) in [
(
PostgreSQL,
"SELECT json_agg(u.a) FILTER (WHERE u.a > (SELECT max(t.x) FROM t)) FROM u",
),
(
PostgreSQL,
"SELECT json_agg(u.a) FILTER (WHERE u.a = ARRAY(SELECT t.x FROM t)) FROM u",
),
(
PostgreSQL,
"SELECT json_agg(u.a ORDER BY (SELECT max(t.x) FROM t)) FROM u",
),
(
Generic,
"SELECT SUM(u.a) OVER (ORDER BY u.a ROWS BETWEEN (SELECT max(t.x) FROM t) \
PRECEDING AND CURRENT ROW) FROM u",
),
(
BigQuery,
"SELECT CAST(u.a AS STRING FORMAT ARRAY_TO_STRING(ARRAY(SELECT t.x FROM t), ',')) FROM u",
),
(
Oracle,
"SELECT CAST(u.a AS NUMBER DEFAULT (SELECT max(t.x) FROM t) ON CONVERSION ERROR) \
FROM u",
),
(
BigQuery,
"SELECT u.a IN UNNEST(ARRAY(SELECT t.x FROM t)) FROM u",
),
] {
let ast = crate::parse(sql, dialect).expect("Failed to parse SQL");
let scope = build_scope(&ast[0]);
assert_eq!(scope.subquery_scopes.len(), 1, "{sql}");
let subquery = &scope.subquery_scopes[0];
assert!(subquery.is_subquery(), "{sql}");
assert!(subquery.sources.contains_key("t"), "{sql}");
assert!(!scope.sources.contains_key("t"), "{sql}");
}
}

#[test]
fn test_nested_and_mixed_subquery_operands_register_once() {
let scope = parse_and_build_scope(
Expand Down