PostgreSQL: Validate session transaction characteristics

Cargo.toml

@@ -18,7 +18,7 @@
 [package]
 name = "sqlparser-dsql"
 description = "SQL parser fork with Aurora DSQL extensions and DSQL-supported PostgreSQL syntax. Based on sqlparser 0.62.0."
-version = "0.62.10"
+version = "0.62.11"
 authors = [
     "Apache DataFusion <dev@datafusion.apache.org>",
     "Amazon Web Services",

src/parser/mod.rs

@@ -15596,9 +15596,16 @@ impl<'a> Parser<'a> {
             }
             .into());
         } else if self.parse_keyword(Keyword::CHARACTERISTICS) {
+            if scope != Some(ContextModifier::Session) {
+                return self.expected_ref("SESSION before CHARACTERISTICS", self.peek_token_ref());
+            }
             self.expect_keywords(&[Keyword::AS, Keyword::TRANSACTION])?;
+            let modes = self.parse_transaction_modes()?;
+            if modes.is_empty() {
+                return self.expected_ref("a transaction mode", self.peek_token_ref());
+            }
             return Ok(Set::SetTransaction {
-                modes: self.parse_transaction_modes()?,
+                modes,
                 snapshot: None,
                 session: true,
             }

tests/sqlparser_postgres.rs

@@ -9687,3 +9687,47 @@ fn dsql_aws_iam_custom_dialect_opt_in() {
     assert!(matches!(statements[0], Statement::AwsIamGrant { .. }));
     assert_eq!(statements[0].to_string(), sql);
 }
+
+#[test]
+fn set_characteristics_requires_session_scope() {
+    for sql in [
+        "SET CHARACTERISTICS AS TRANSACTION READ ONLY",
+        "SET CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL REPEATABLE READ",
+        "SET LOCAL CHARACTERISTICS AS TRANSACTION READ ONLY",
+        "SET LOCAL CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL SERIALIZABLE",
+        "SET GLOBAL CHARACTERISTICS AS TRANSACTION READ WRITE",
+        "SET GLOBAL CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL SERIALIZABLE",
+    ] {
+        assert!(pg_and_generic().parse_sql_statements(sql).is_err(), "{sql}");
+    }
+}
+
+#[test]
+fn set_session_characteristics_preserves_transaction_modes() {
+    let sql =
+        "SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL REPEATABLE READ, READ ONLY";
+    let Statement::Set(Set::SetTransaction {
+        modes,
+        snapshot,
+        session,
+    }) = pg_and_generic().verified_stmt(sql)
+    else {
+        panic!("expected session transaction characteristics");
+    };
+    assert!(session);
+    assert!(snapshot.is_none());
+    assert_eq!(
+        modes,
+        vec![
+            TransactionMode::IsolationLevel(TransactionIsolationLevel::RepeatableRead),
+            TransactionMode::AccessMode(TransactionAccessMode::ReadOnly),
+        ]
+    );
+}
+
+#[test]
+fn set_session_characteristics_requires_transaction_mode() {
+    assert!(pg_and_generic()
+        .parse_sql_statements("SET SESSION CHARACTERISTICS AS TRANSACTION")
+        .is_err());
+}