Move WriteResult to mod

Summary:
Up until this diff the implementation of WriteResult was in the `fbmysql_wrapper`. However the implementation can be used for any mysql implemntation as it is very simple.
Here I extract it to the `mod.rs` file so I can reuse it for the external mysql version later in the stack

Reviewed By: gustavoavena

Differential Revision: D50838010

fbshipit-source-id: 8e9246b116634fbae42c65737482f0ab864650b4

shed/sql/common/mysql/mod.rs

@@ -34,8 +34,6 @@ pub use facebook::TransactionResult;
 pub use facebook::TryFromRowField;
 #[cfg(fbcode_build)]
 pub use facebook::ValueError;
-#[cfg(fbcode_build)]
-pub use facebook::WriteResult;
 pub use mysql_derive::OptTryFromRowField;
 pub use mysql_derive::TryFromRowField;
 #[cfg(not(fbcode_build))]
@@ -58,8 +56,6 @@ pub use mysql_stub::TransactionResult;
 pub use mysql_stub::TryFromRowField;
 #[cfg(not(fbcode_build))]
 pub use mysql_stub::ValueError;
-#[cfg(not(fbcode_build))]
-pub use mysql_stub::WriteResult;
 
 use super::WriteResult as SqlWriteResult;
 
@@ -154,6 +150,26 @@ pub enum IsolationLevel {
     ReadCommitted,
 }
 
+/// Result returned by a write query
+pub struct WriteResult(u64, u64);
+
+impl WriteResult {
+    /// Create result
+    pub fn new(last_insert_id: u64, rows_affected: u64) -> Self {
+        WriteResult(last_insert_id, rows_affected)
+    }
+
+    /// Get last inserted id
+    pub fn last_insert_id(&self) -> u64 {
+        self.0
+    }
+
+    /// Get number of affected rows
+    pub fn rows_affected(&self) -> u64 {
+        self.1
+    }
+}
+
 impl From<WriteResult> for SqlWriteResult {
     fn from(result: WriteResult) -> Self {
         Self::new(Some(result.last_insert_id()), result.rows_affected())

shed/sql/common/mysql/mysql_stub/mod.rs

@@ -15,6 +15,7 @@ use std::fmt::Display;
 use thiserror::Error;
 
 use crate::mysql::IsolationLevel;
+use crate::mysql::WriteResult;
 
 /// Error for Mysql client
 #[derive(Error, Debug)]
@@ -42,20 +43,6 @@ impl From<ValueError> for MysqlError {
     }
 }
 
-/// Result returned by a write query
-pub struct WriteResult;
-
-impl WriteResult {
-    /// Get last inserted id
-    pub fn last_insert_id(&self) -> u64 {
-        unimplemented!("This is a stub");
-    }
-    /// Get number of affected rows
-    pub fn rows_affected(&self) -> u64 {
-        unimplemented!("This is a stub");
-    }
-}
-
 /// ODS counters
 pub struct ConnectionStats;