From 338c0b09276bbfce7a75bc439914947bde6dc750 Mon Sep 17 00:00:00 2001
From: Paul Mason <paul@paulmason.me>
Date: Sat, 10 Feb 2024 12:08:06 -0800
Subject: [PATCH] Prevent scale of 29 from postgresql hydration

---
 src/postgres/common.rs |  2 +-
 src/postgres/driver.rs | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/src/postgres/common.rs b/src/postgres/common.rs
index 3922b7d..485a259 100644
--- a/src/postgres/common.rs
+++ b/src/postgres/common.rs
@@ -78,7 +78,7 @@ impl Decimal {
 
         result.set_sign_negative(neg);
         // Rescale to the postgres value, automatically rounding as needed.
-        result.rescale(scale as u32);
+        result.rescale((scale as u32).min(MAX_PRECISION_U32));
         result
     }
 
diff --git a/src/postgres/driver.rs b/src/postgres/driver.rs
index 1aafd78..1adac5a 100644
--- a/src/postgres/driver.rs
+++ b/src/postgres/driver.rs
@@ -255,6 +255,43 @@ mod test {
         assert_eq!(Decimal::ZERO, result);
     }
 
+    #[test]
+    fn read_small_unconstrained_numeric_type() {
+        let mut client = match Client::connect(&get_postgres_url(), NoTls) {
+            Ok(x) => x,
+            Err(err) => panic!("{:#?}", err),
+        };
+        let result: Decimal = match client.query("SELECT 0.100000000000000000000000000001::NUMERIC", &[]) {
+            Ok(x) => x.first().unwrap().get(0),
+            Err(err) => panic!("error - {:#?}", err),
+        };
+
+        // This gets rounded to 28 decimal places. In the future we may want to introduce a global feature which
+        // prevents rounding.
+        assert_eq!(result.to_string(), "0.1000000000000000000000000000");
+        assert_eq!(result.scale(), 28);
+    }
+
+    #[test]
+    fn read_small_unconstrained_numeric_type_addition() {
+        let mut client = match Client::connect(&get_postgres_url(), NoTls) {
+            Ok(x) => x,
+            Err(err) => panic!("{:#?}", err),
+        };
+        let (a, b): (Decimal, Decimal) = match client.query(
+            "SELECT 0.100000000000000000000000000001::NUMERIC, 0.00000000000014780214::NUMERIC",
+            &[],
+        ) {
+            Ok(x) => {
+                let row = x.first().unwrap();
+                (row.get(0), row.get(1))
+            }
+            Err(err) => panic!("error - {:#?}", err),
+        };
+
+        assert_eq!(a + b, Decimal::from_str("0.1000000000001478021400000000").unwrap());
+    }
+
     #[test]
     fn read_numeric_type() {
         let mut client = match Client::connect(&get_postgres_url(), NoTls) {