From 1914d72b0096326244b9d1f94fad073a753a29c5 Mon Sep 17 00:00:00 2001
From: Petr Novotnik <petr.novotnik@mgm-tp.com>
Date: Mon, 1 Dec 2025 18:03:23 +0100
Subject: [PATCH] [Oracle] Lower StringConcat precedence

---
 src/ast/query.rs          |  9 +++++
 src/dialect/oracle.rs     | 38 +++++++++++++++++-
 tests/sqlparser_oracle.rs | 81 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+), 1 deletion(-)
 create mode 100644 tests/sqlparser_oracle.rs

diff --git a/src/ast/query.rs b/src/ast/query.rs
index 16fc9ec0..67972f25 100644
--- a/src/ast/query.rs
+++ b/src/ast/query.rs
@@ -174,6 +174,15 @@ impl SetExpr {
             None
         }
     }
+
+    /// If this `SetExpr` is a `SELECT`, returns a mutable [`Select`].
+    pub fn as_select_mut(&mut self) -> Option<&mut Select> {
+        if let Self::Select(select) = self {
+            Some(&mut **select)
+        } else {
+            None
+        }
+    }
 }
 
 impl fmt::Display for SetExpr {
diff --git a/src/dialect/oracle.rs b/src/dialect/oracle.rs
index 0d6aee5e..10387d63 100644
--- a/src/dialect/oracle.rs
+++ b/src/dialect/oracle.rs
@@ -15,7 +15,14 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use super::Dialect;
+use log::debug;
+
+use crate::{
+    parser::{Parser, ParserError},
+    tokenizer::Token,
+};
+
+use super::{Dialect, Precedence};
 
 /// A [`Dialect`] for [Oracle Databases](https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/index.html)
 #[derive(Debug)]
@@ -75,6 +82,35 @@ impl Dialect for OracleDialect {
         true
     }
 
+    fn get_next_precedence(&self, _parser: &Parser) -> Option<Result<u8, ParserError>> {
+        let t = _parser.peek_token();
+        debug!("get_next_precedence() {t:?}");
+
+        match t.token {
+            Token::StringConcat => Some(Ok(self.prec_value(Precedence::PlusMinus))),
+            _ => None,
+        }
+    }
+
+    fn prec_value(&self, prec: Precedence) -> u8 {
+        match prec {
+            Precedence::Period => 100,
+            Precedence::DoubleColon => 50,
+            Precedence::AtTz => 41,
+            Precedence::MulDivModOp => 40,
+            Precedence::PlusMinus => 30,
+            Precedence::Xor => 24,
+            Precedence::Ampersand => 23,
+            Precedence::Caret => 22,
+            Precedence::Pipe => 21,
+            Precedence::Between | Precedence::Eq | Precedence::Like | Precedence::Is => 20,
+            Precedence::PgOther => 16,
+            Precedence::UnaryNot => 15,
+            Precedence::And => 10,
+            Precedence::Or => 5,
+        }
+    }
+
     fn supports_group_by_expr(&self) -> bool {
         true
     }
diff --git a/tests/sqlparser_oracle.rs b/tests/sqlparser_oracle.rs
new file mode 100644
index 00000000..d9a3357f
--- /dev/null
+++ b/tests/sqlparser_oracle.rs
@@ -0,0 +1,81 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#![warn(clippy::all)]
+//! Test SQL syntax, specific to [sqlparser::dialect::OracleDialect].
+
+extern crate core;
+
+#[cfg(test)]
+use pretty_assertions::assert_eq;
+
+use sqlparser::{
+    ast::{Expr, SelectItem, Value},
+    dialect::OracleDialect,
+};
+#[cfg(test)]
+use test_utils::TestedDialects;
+
+mod test_utils;
+
+#[test]
+fn muldiv_have_higher_precedence_than_strconcat() {
+    // ~ oracle: `||` has a lower precedence than `*` and `/`
+    let sql = "SELECT 3 / 5 || 'asdf' || 7 * 9 FROM dual";
+    let mut query = oracle_dialect().verified_query(sql);
+    nest_binary_ops(&mut query.body.as_select_mut().expect("not a SELECT").projection[0]);
+    assert_eq!(
+        &format!("{query}"),
+        "SELECT (((3 / 5) || 'asdf') || (7 * 9)) FROM dual"
+    );
+}
+
+#[test]
+fn plusminus_have_same_precedence_as_strconcat() {
+    // ~ oracle: `+`, `-`, and `||` have the same precedence and parse from left-to-right
+    let sql = "SELECT 3 + 5 || '.3' || 7 - 9 FROM dual";
+    let mut query = oracle_dialect().verified_query(sql);
+    nest_binary_ops(&mut query.body.as_select_mut().expect("not a SELECT").projection[0]);
+    assert_eq!(
+        &format!("{query}"),
+        "SELECT ((((3 + 5) || '.3') || 7) - 9) FROM dual"
+    );
+}
+
+fn oracle_dialect() -> TestedDialects {
+    TestedDialects::new(vec![Box::new(OracleDialect)])
+}
+
+/// Wraps [Expr::BinaryExpr]s in `item` with a [Expr::Nested] recursively.
+fn nest_binary_ops(item: &mut SelectItem) {
+    // ~ idealy, we could use `VisitorMut` at this point
+    fn nest(expr: &mut Expr) {
+        // ~ ideally we could use VisitorMut here
+        if let Expr::BinaryOp { left, op: _, right } = expr {
+            nest(&mut *left);
+            nest(&mut *right);
+            let inner = std::mem::replace(expr, Expr::Value(Value::Null.into()));
+            *expr = Expr::Nested(Box::new(inner));
+        }
+    }
+    match item {
+        SelectItem::UnnamedExpr(expr) => nest(expr),
+        SelectItem::ExprWithAlias { expr, alias: _ } => nest(expr),
+        SelectItem::QualifiedWildcard(_, _) => {}
+        SelectItem::Wildcard(_) => {}
+    }
+}