Separate raw value representations of postgresql and mysql backend

This commit separates the raw value representation of the mysql and
postgresql backend from raw `&[u8]` to specific types that could hold
additional information. To avoid code duplication for commonly used
types an additional trait (`BinaryRawValue`) is introduced, which is
basically equivalent to `AsRef<[u8]>` but has the existing
`HasRawValue` trait as super trait. This is required to workaround
some higher ranked life time issues in rustc.
Additionally some type information are added to the postgresql value
type. Those information may allow to do dynamic type conversations in
future diesel versions.

Author: weiznich

diesel/src/backend.rs

@@ -60,6 +60,12 @@ pub trait HasRawValue<'a> {
     type RawValue;
 }
 
+/// A trait indicating that the provided raw value uses a binary representation internally
+pub trait BinaryRawValue<'a>: HasRawValue<'a> {
+    /// Get the underlying binary representation of the raw value
+    fn as_bytes(value: Self::RawValue) -> &'a [u8];
+}
+
 /// A helper type to get the raw representation of a database type given to
 /// `FromSql`. Equivalent to `<DB as Backend>::RawValue<'a>`.
 pub type RawValue<'a, DB> = <DB as HasRawValue<'a>>::RawValue;

diesel/src/mysql/backend.rs

@@ -3,6 +3,7 @@
 use byteorder::NativeEndian;
 
 use super::query_builder::MysqlQueryBuilder;
+use super::MysqlValue;
 use backend::*;
 use query_builder::bind_collector::RawBytesBindCollector;
 use sql_types::TypeMetadata;
@@ -69,7 +70,7 @@ impl Backend for Mysql {
 }
 
 impl<'a> HasRawValue<'a> for Mysql {
-    type RawValue = &'a [u8];
+    type RawValue = MysqlValue<'a>;
 }
 
 impl TypeMetadata for Mysql {

diesel/src/mysql/connection/bind.rs

@@ -4,7 +4,7 @@ use std::mem;
 use std::os::raw as libc;
 
 use super::stmt::Statement;
-use mysql::{MysqlType, MysqlTypeMetadata};
+use mysql::{MysqlType, MysqlTypeMetadata, MysqlValue};
 use result::QueryResult;
 
 pub struct Binds {
@@ -23,7 +23,7 @@ impl Binds {
             })
             .collect();
 
-        Binds { data: data }
+        Binds { data }
     }
 
     pub fn from_output_types(types: Vec<MysqlTypeMetadata>) -> Self {
@@ -38,7 +38,7 @@ impl Binds {
             .map(BindData::for_output)
             .collect();
 
-        Binds { data: data }
+        Binds { data }
     }
 
     pub fn from_result_metadata(fields: &[ffi::MYSQL_FIELD]) -> Self {
@@ -86,8 +86,8 @@ impl Binds {
         }
     }
 
-    pub fn field_data(&self, idx: usize) -> Option<&[u8]> {
-        self.data[idx].bytes()
+    pub fn field_data(&self, idx: usize) -> Option<MysqlValue> {
+        self.data[idx].bytes().map(MysqlValue::new)
     }
 }
 

diesel/src/mysql/connection/stmt/iterator.rs

@@ -1,7 +1,7 @@
 use std::collections::HashMap;
 
 use super::{ffi, libc, Binds, Statement, StatementMetadata};
-use mysql::{Mysql, MysqlTypeMetadata};
+use mysql::{Mysql, MysqlTypeMetadata, MysqlValue};
 use result::QueryResult;
 use row::*;
 
@@ -18,10 +18,7 @@ impl<'a> StatementIterator<'a> {
 
         execute_statement(stmt, &mut output_binds)?;
 
-        Ok(StatementIterator {
-            stmt: stmt,
-            output_binds: output_binds,
-        })
+        Ok(StatementIterator { stmt, output_binds })
     }
 
     pub fn map<F, T>(mut self, mut f: F) -> QueryResult<Vec<T>>
@@ -53,7 +50,7 @@ pub struct MysqlRow<'a> {
 }
 
 impl<'a> Row<Mysql> for MysqlRow<'a> {
-    fn take(&mut self) -> Option<&[u8]> {
+    fn take(&mut self) -> Option<MysqlValue> {
         let current_idx = self.col_idx;
         self.col_idx += 1;
         self.binds.field_data(current_idx)
@@ -119,7 +116,7 @@ impl<'a> NamedRow<Mysql> for NamedMysqlRow<'a> {
         self.column_indices.get(column_name).cloned()
     }
 
-    fn get_raw_value(&self, idx: usize) -> Option<&[u8]> {
+    fn get_raw_value(&self, idx: usize) -> Option<MysqlValue> {
         self.binds.field_data(idx)
     }
 }

diesel/src/mysql/mod.rs

@@ -6,10 +6,12 @@
 
 mod backend;
 mod connection;
+mod value;
 
 mod query_builder;
 pub mod types;
 
 pub use self::backend::{Mysql, MysqlType, MysqlTypeMetadata};
 pub use self::connection::MysqlConnection;
 pub use self::query_builder::MysqlQueryBuilder;
+pub use self::value::MysqlValue;

diesel/src/mysql/types/date_and_time.rs

@@ -7,7 +7,7 @@ use std::os::raw as libc;
 use std::{mem, ptr, slice};
 
 use deserialize::{self, FromSql};
-use mysql::Mysql;
+use mysql::{Mysql, MysqlValue};
 use serialize::{self, IsNull, Output, ToSql};
 use sql_types::{Date, Datetime, Time, Timestamp};
 
@@ -25,9 +25,9 @@ macro_rules! mysql_time_impls {
         }
 
         impl FromSql<$ty, Mysql> for ffi::MYSQL_TIME {
-            fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
-                let bytes = not_none!(bytes);
-                let bytes_ptr = bytes.as_ptr() as *const ffi::MYSQL_TIME;
+            fn from_sql(value: Option<MysqlValue>) -> deserialize::Result<Self> {
+                let value = not_none!(value);
+                let bytes_ptr = value.as_bytes().as_ptr() as *const ffi::MYSQL_TIME;
                 unsafe {
                     let mut result = mem::MaybeUninit::uninit();
                     ptr::copy_nonoverlapping(bytes_ptr, result.as_mut_ptr(), 1);
@@ -55,7 +55,7 @@ impl ToSql<Datetime, Mysql> for NaiveDateTime {
 }
 
 impl FromSql<Datetime, Mysql> for NaiveDateTime {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
         <NaiveDateTime as FromSql<Timestamp, Mysql>>::from_sql(bytes)
     }
 }
@@ -77,7 +77,7 @@ impl ToSql<Timestamp, Mysql> for NaiveDateTime {
 }
 
 impl FromSql<Timestamp, Mysql> for NaiveDateTime {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
         let mysql_time = <ffi::MYSQL_TIME as FromSql<Timestamp, Mysql>>::from_sql(bytes)?;
 
         NaiveDate::from_ymd_opt(
@@ -110,7 +110,7 @@ impl ToSql<Time, Mysql> for NaiveTime {
 }
 
 impl FromSql<Time, Mysql> for NaiveTime {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
         let mysql_time = <ffi::MYSQL_TIME as FromSql<Time, Mysql>>::from_sql(bytes)?;
         NaiveTime::from_hms_opt(
             mysql_time.hour as u32,
@@ -134,7 +134,7 @@ impl ToSql<Date, Mysql> for NaiveDate {
 }
 
 impl FromSql<Date, Mysql> for NaiveDate {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
         let mysql_time = <ffi::MYSQL_TIME as FromSql<Date, Mysql>>::from_sql(bytes)?;
         NaiveDate::from_ymd_opt(
             mysql_time.year as i32,

diesel/src/mysql/types/mod.rs

@@ -8,7 +8,7 @@ use byteorder::WriteBytesExt;
 use std::io::Write;
 
 use deserialize::{self, FromSql};
-use mysql::{Mysql, MysqlTypeMetadata};
+use mysql::{Mysql, MysqlTypeMetadata, MysqlValue};
 use serialize::{self, IsNull, Output, ToSql};
 use sql_types::*;
 
@@ -19,8 +19,9 @@ impl ToSql<TinyInt, Mysql> for i8 {
 }
 
 impl FromSql<TinyInt, Mysql> for i8 {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
-        let bytes = not_none!(bytes);
+    fn from_sql(value: Option<MysqlValue>) -> deserialize::Result<Self> {
+        let value = not_none!(value);
+        let bytes = value.as_bytes();
         Ok(bytes[0] as i8)
     }
 }
@@ -36,7 +37,7 @@ impl ToSql<Unsigned<TinyInt>, Mysql> for u8 {
 }
 
 impl FromSql<Unsigned<TinyInt>, Mysql> for u8 {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
         let signed: i8 = FromSql::<TinyInt, Mysql>::from_sql(bytes)?;
         Ok(signed as u8)
     }
@@ -49,7 +50,7 @@ impl ToSql<Unsigned<SmallInt>, Mysql> for u16 {
 }
 
 impl FromSql<Unsigned<SmallInt>, Mysql> for u16 {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
         let signed: i16 = FromSql::<SmallInt, Mysql>::from_sql(bytes)?;
         Ok(signed as u16)
     }
@@ -62,7 +63,7 @@ impl ToSql<Unsigned<Integer>, Mysql> for u32 {
 }
 
 impl FromSql<Unsigned<Integer>, Mysql> for u32 {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
         let signed: i32 = FromSql::<Integer, Mysql>::from_sql(bytes)?;
         Ok(signed as u32)
     }
@@ -75,7 +76,7 @@ impl ToSql<Unsigned<BigInt>, Mysql> for u64 {
 }
 
 impl FromSql<Unsigned<BigInt>, Mysql> for u64 {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
         let signed: i64 = FromSql::<BigInt, Mysql>::from_sql(bytes)?;
         Ok(signed as u64)
     }
@@ -89,8 +90,8 @@ impl ToSql<Bool, Mysql> for bool {
 }
 
 impl FromSql<Bool, Mysql> for bool {
-    fn from_sql(bytes: Option<&[u8]>) -> deserialize::Result<Self> {
-        Ok(not_none!(bytes).iter().any(|x| *x != 0))
+    fn from_sql(bytes: Option<MysqlValue>) -> deserialize::Result<Self> {
+        Ok(not_none!(bytes).as_bytes().iter().any(|x| *x != 0))
     }
 }
 

diesel/src/mysql/value.rs

@@ -0,0 +1,25 @@
+use super::Mysql;
+use backend::BinaryRawValue;
+
+/// Raw mysql value as received from the database
+#[derive(Copy, Clone, Debug)]
+pub struct MysqlValue<'a> {
+    raw: &'a [u8],
+}
+
+impl<'a> MysqlValue<'a> {
+    pub(crate) fn new(raw: &'a [u8]) -> Self {
+        Self { raw }
+    }
+
+    /// Get the underlying raw byte representation
+    pub fn as_bytes(&self) -> &[u8] {
+        self.raw
+    }
+}
+
+impl<'a> BinaryRawValue<'a> for Mysql {
+    fn as_bytes(value: Self::RawValue) -> &'a [u8] {
+        value.raw
+    }
+}

diesel/src/pg/backend.rs

@@ -3,7 +3,7 @@
 use byteorder::NetworkEndian;
 
 use super::query_builder::PgQueryBuilder;
-use super::PgMetadataLookup;
+use super::{PgMetadataLookup, PgValue};
 use backend::*;
 use deserialize::Queryable;
 use query_builder::bind_collector::RawBytesBindCollector;
@@ -43,7 +43,7 @@ impl Backend for Pg {
 }
 
 impl<'a> HasRawValue<'a> for Pg {
-    type RawValue = &'a [u8];
+    type RawValue = PgValue<'a>;
 }
 
 impl TypeMetadata for Pg {

diesel/src/pg/connection/cursor.rs

@@ -20,7 +20,7 @@ impl<ST, T> Cursor<ST, T> {
     pub fn new(db_result: PgResult) -> Self {
         Cursor {
             current_row: 0,
-            db_result: db_result,
+            db_result,
             _marker: PhantomData,
         }
     }
@@ -47,7 +47,7 @@ where
 }
 
 pub struct NamedCursor {
-    db_result: PgResult,
+    pub(crate) db_result: PgResult,
 }
 
 impl NamedCursor {