Add increment method

ensemble/src/lib.rs

@@ -158,6 +158,7 @@ pub trait Model: DeserializeOwned + Serialize + Sized + Send + Sync + Debug + De
 		Self::query().with(eager_load)
 	}
 
+	/// Load a relationship for the model.
 	fn load<T: Into<EagerLoad> + Send>(
 		&mut self,
 		relation: T,
@@ -173,6 +174,29 @@ pub trait Model: DeserializeOwned + Serialize + Sized + Send + Sync + Debug + De
 		}
 	}
 
+	fn increment(
+		&mut self,
+		column: &str,
+		amount: u64,
+	) -> impl Future<Output = Result<(), Error>> + Send {
+		async move {
+			let rows_affected = Self::query()
+				.r#where(
+					Self::PRIMARY_KEY,
+					"=",
+					value::for_db(self.primary_key()).unwrap(),
+				)
+				.increment(column, amount)
+				.await?;
+
+			if rows_affected != 1 {
+				return Err(Error::UniqueViolation);
+			}
+
+			Ok(())
+		}
+	}
+
 	/// Convert the model to a JSON value.
 	///
 	/// # Panics

ensemble/src/query.rs

@@ -421,6 +421,31 @@ impl Builder {
 		Ok(rbs::from_value(result.last_insert_id)?)
 	}
 
+	/// Increment a column's value by a given amount. Returns the number of affected rows.
+	///
+	/// # Errors
+	///
+	/// Returns an error if the query fails, or if a connection to the database cannot be established.
+	pub async fn increment(self, column: &str, amount: u64) -> Result<u64, Error> {
+		let mut conn = connection::get().await?;
+		let (sql, mut bindings) = (
+			format!(
+				"UPDATE {} SET {column} = {column} + ? {}",
+				self.table,
+				self.to_sql(Type::Update)
+			),
+			self.get_bindings(),
+		);
+		bindings.insert(0, amount.into());
+
+		tracing::debug!(sql = sql.as_str(), bindings = ?bindings, "Executing UPDATE SQL query for increment");
+
+		conn.exec(&sql, bindings)
+			.await
+			.map_err(|e| Error::Database(e.to_string()))
+			.map(|r| r.rows_affected)
+	}
+
 	/// Update records in the database. Returns the number of affected rows.
 	///
 	/// # Errors