Add #[recursive] (#1522)

Co-authored-by: Ifeanyi Ubah <[email protected]>

Cargo.toml

@@ -37,15 +37,18 @@ name = "sqlparser"
 path = "src/lib.rs"
 
 [features]
-default = ["std"]
+default = ["std", "recursive-protection"]
 std = []
+recursive-protection = ["std", "recursive"]
 # Enable JSON output in the `cli` example:
 json_example = ["serde_json", "serde"]
 visitor = ["sqlparser_derive"]
 
 [dependencies]
 bigdecimal = { version = "0.4.1", features = ["serde"], optional = true }
 log = "0.4"
+recursive = { version = "0.1.1", optional = true}
+
 serde = { version = "1.0", features = ["derive"], optional = true }
 # serde_json is only used in examples/cli, but we have to put it outside
 # of dev-dependencies because of

README.md

@@ -63,7 +63,7 @@ The following optional [crate  features](https://doc.rust-lang.org/cargo/referen
 
 * `serde`: Adds [Serde](https://serde.rs/) support by implementing  `Serialize` and `Deserialize` for all AST nodes.
 * `visitor`: Adds a `Visitor` capable of recursively walking the AST tree.
-
+* `recursive-protection` (enabled by default), uses [recursive](https://docs.rs/recursive/latest/recursive/) for stack overflow protection. 
 
 ## Syntax vs Semantics
 

derive/src/lib.rs

@@ -78,7 +78,10 @@ fn derive_visit(input: proc_macro::TokenStream, visit_type: &VisitType) -> proc_
 
     let expanded = quote! {
         // The generated impl.
+        // Note that it uses [`recursive::recursive`] to protect from stack overflow.
+        // See tests in https://github.com/apache/datafusion-sqlparser-rs/pull/1522/ for more info.
         impl #impl_generics sqlparser::ast::#visit_trait for #name #ty_generics #where_clause {
+             #[cfg_attr(feature = "recursive-protection", recursive::recursive)]
             fn visit<V: sqlparser::ast::#visitor_trait>(
                 &#modifier self,
                 visitor: &mut V

sqlparser_bench/benches/sqlparser_bench.rs

@@ -42,6 +42,46 @@ fn basic_queries(c: &mut Criterion) {
     group.bench_function("sqlparser::with_select", |b| {
         b.iter(|| Parser::parse_sql(&dialect, with_query).unwrap());
     });
+
+    let large_statement = {
+        let expressions = (0..1000)
+            .map(|n| format!("FN_{}(COL_{})", n, n))
+            .collect::<Vec<_>>()
+            .join(", ");
+        let tables = (0..1000)
+            .map(|n| format!("TABLE_{}", n))
+            .collect::<Vec<_>>()
+            .join(" JOIN ");
+        let where_condition = (0..1000)
+            .map(|n| format!("COL_{} = {}", n, n))
+            .collect::<Vec<_>>()
+            .join(" OR ");
+        let order_condition = (0..1000)
+            .map(|n| format!("COL_{} DESC", n))
+            .collect::<Vec<_>>()
+            .join(", ");
+
+        format!(
+            "SELECT {} FROM {} WHERE {} ORDER BY {}",
+            expressions, tables, where_condition, order_condition
+        )
+    };
+
+    group.bench_function("parse_large_statement", |b| {
+        b.iter(|| Parser::parse_sql(&dialect, criterion::black_box(large_statement.as_str())));
+    });
+
+    let large_statement = Parser::parse_sql(&dialect, large_statement.as_str())
+        .unwrap()
+        .pop()
+        .unwrap();
+
+    group.bench_function("format_large_statement", |b| {
+        b.iter(|| {
+            let formatted_query = large_statement.to_string();
+            assert_eq!(formatted_query, large_statement);
+        });
+    });
 }
 
 criterion_group!(benches, basic_queries);

src/ast/mod.rs

@@ -1291,6 +1291,7 @@ impl fmt::Display for CastFormat {
 }
 
 impl fmt::Display for Expr {
+    #[cfg_attr(feature = "recursive-protection", recursive::recursive)]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
             Expr::Identifier(s) => write!(f, "{s}"),

src/ast/visitor.rs

@@ -894,4 +894,29 @@ mod tests {
             assert_eq!(actual, expected)
         }
     }
+
+    struct QuickVisitor; // [`TestVisitor`] is too slow to iterate over thousands of nodes
+
+    impl Visitor for QuickVisitor {
+        type Break = ();
+    }
+
+    #[test]
+    fn overflow() {
+        let cond = (0..1000)
+            .map(|n| format!("X = {}", n))
+            .collect::<Vec<_>>()
+            .join(" OR ");
+        let sql = format!("SELECT x where {0}", cond);
+
+        let dialect = GenericDialect {};
+        let tokens = Tokenizer::new(&dialect, sql.as_str()).tokenize().unwrap();
+        let s = Parser::new(&dialect)
+            .with_tokens(tokens)
+            .parse_statement()
+            .unwrap();
+
+        let mut visitor = QuickVisitor {};
+        s.visit(&mut visitor);
+    }
 }

src/parser/mod.rs

@@ -73,6 +73,9 @@ mod recursion {
     /// Note: Uses an [`std::rc::Rc`] and [`std::cell::Cell`] in order to satisfy the Rust
     /// borrow checker so the automatic [`DepthGuard`] decrement a
     /// reference to the counter.
+    ///
+    /// Note: when "recursive-protection" feature is enabled, this crate uses additional stack overflow protection
+    /// for some of its recursive methods. See [`recursive::recursive`] for more information.
     pub(crate) struct RecursionCounter {
         remaining_depth: Rc<Cell<usize>>,
     }
@@ -326,6 +329,9 @@ impl<'a> Parser<'a> {
     /// # Ok(())
     /// # }
     /// ```
+    ///
+    /// Note: when "recursive-protection" feature is enabled, this crate uses additional stack overflow protection
+    //  for some of its recursive methods. See [`recursive::recursive`] for more information.
     pub fn with_recursion_limit(mut self, recursion_limit: usize) -> Self {
         self.recursion_counter = RecursionCounter::new(recursion_limit);
         self

tests/sqlparser_common.rs

@@ -12433,3 +12433,16 @@ fn test_table_sample() {
     dialects.verified_stmt("SELECT * FROM tbl AS t TABLESAMPLE SYSTEM (50)");
     dialects.verified_stmt("SELECT * FROM tbl AS t TABLESAMPLE SYSTEM (50) REPEATABLE (10)");
 }
+
+#[test]
+fn overflow() {
+    let expr = std::iter::repeat("1")
+        .take(1000)
+        .collect::<Vec<_>>()
+        .join(" + ");
+    let sql = format!("SELECT {}", expr);
+
+    let mut statements = Parser::parse_sql(&GenericDialect {}, sql.as_str()).unwrap();
+    let statement = statements.pop().unwrap();
+    assert_eq!(statement.to_string(), sql);
+}