Moveable binds and rows

diesel/src/connection/mod.rs

@@ -14,6 +14,7 @@ use crate::backend::Backend;
 use crate::expression::QueryMetadata;
 use crate::query_builder::{Query, QueryFragment, QueryId};
 use crate::result::*;
+use crate::sql_types::TypeMetadata;
 use std::fmt::Debug;
 
 #[doc(inline)]
@@ -444,6 +445,15 @@ pub trait LoadConnection<B = DefaultLoadingMode>: Connection {
         Self::Backend: QueryMetadata<T::SqlType>;
 }
 
+/// Describes a connection with an underlying [`crate::sql_types::TypeMetadata::MetadataLookup`]
+#[diesel_derives::__diesel_public_if(
+    feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
+)]
+pub trait WithMetadataLookup: Connection {
+    /// Retrieves the underlying metadata lookup
+    fn metadata_lookup(&mut self) -> &mut <Self::Backend as TypeMetadata>::MetadataLookup;
+}
+
 /// A variant of the [`Connection`](trait.Connection.html) trait that is
 /// usable with dynamic dispatch
 ///

diesel/src/query_builder/ast_pass.rs

@@ -1,7 +1,7 @@
 use std::fmt;
 
 use crate::backend::Backend;
-use crate::query_builder::{BindCollector, QueryBuilder};
+use crate::query_builder::{BindCollector, MoveableBindCollector, QueryBuilder};
 use crate::result::QueryResult;
 use crate::serialize::ToSql;
 use crate::sql_types::HasSqlType;
@@ -252,6 +252,35 @@ where
         Ok(())
     }
 
+    /// Push bind collector values from its data onto the query
+    ///
+    /// This method works with [MoveableBindCollector] data [MoveableBindCollector::BindData]
+    /// and is used with already collected query meaning its SQL is already built and its
+    /// bind data already collected.
+    #[diesel_derives::__diesel_public_if(
+        feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
+    )]
+    pub(crate) fn push_bind_collector_data<MD>(
+        &mut self,
+        bind_collector_data: &MD,
+    ) -> QueryResult<()>
+    where
+        DB: Backend,
+        for<'bc> DB::BindCollector<'bc>: MoveableBindCollector<DB, BindData = MD>,
+    {
+        match self.internals {
+            AstPassInternals::CollectBinds {
+                ref mut collector,
+                metadata_lookup: _,
+            } => collector.append_bind_data(bind_collector_data),
+            AstPassInternals::DebugBinds(ref mut f) => {
+                f.push(Box::new("Opaque bind collector data"))
+            }
+            _ => {}
+        }
+        Ok(())
+    }
+
     /// Get information about the backend that will consume this query
     #[cfg_attr(
         not(feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"),

diesel/src/query_builder/bind_collector.rs

@@ -46,6 +46,23 @@ pub trait BindCollector<'a, DB: TypeMetadata>: Sized {
     }
 }
 
+/// A movable version of the bind collector which allows it to be extracted, moved and refilled.
+///
+/// This is mostly useful in async context where bind data needs to be moved across threads.
+#[diesel_derives::__diesel_public_if(
+    feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
+)]
+pub trait MoveableBindCollector<DB: TypeMetadata> {
+    /// The movable bind data of this bind collector
+    type BindData: Send + 'static;
+
+    /// Builds a movable version of the bind collector
+    fn moveable(&self) -> Self::BindData;
+
+    /// Refill the bind collector with its bind data
+    fn append_bind_data(&mut self, from: &Self::BindData);
+}
+
 #[derive(Debug)]
 /// A bind collector used by backends which transmit bind parameters as an
 /// opaque blob of bytes.
@@ -125,6 +142,26 @@ where
     }
 }
 
+impl<DB> MoveableBindCollector<DB> for RawBytesBindCollector<DB>
+where
+    for<'a> DB: Backend<BindCollector<'a> = Self> + TypeMetadata + 'static,
+    <DB as TypeMetadata>::TypeMetadata: Clone + Send,
+{
+    type BindData = Self;
+
+    fn moveable(&self) -> Self::BindData {
+        RawBytesBindCollector {
+            binds: self.binds.clone(),
+            metadata: self.metadata.clone(),
+        }
+    }
+
+    fn append_bind_data(&mut self, from: &Self::BindData) {
+        self.binds.extend(from.binds.iter().cloned());
+        self.metadata.extend(from.metadata.clone());
+    }
+}
+
 // This is private for now as we may want to add `Into` impls for the wrapper type
 // later on
 mod private {

diesel/src/query_builder/collected_query.rs

@@ -0,0 +1,51 @@
+use super::{AstPass, MoveableBindCollector, Query, QueryFragment, QueryId};
+use crate::backend::{Backend, DieselReserveSpecialization};
+use crate::result::QueryResult;
+use crate::sql_types::Untyped;
+
+#[derive(Debug)]
+#[must_use = "Queries are only executed when calling `load`, `get_result` or similar."]
+/// A SQL query variant with already collected bind data which can be moved
+#[diesel_derives::__diesel_public_if(
+    feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
+)]
+pub struct CollectedQuery<T> {
+    sql: String,
+    safe_to_cache_prepared: bool,
+    bind_data: T,
+}
+
+impl<T> CollectedQuery<T> {
+    /// Builds a [CollectedQuery] with movable bind data
+    pub fn new(sql: String, safe_to_cache_prepared: bool, bind_data: T) -> Self {
+        Self {
+            sql,
+            safe_to_cache_prepared,
+            bind_data,
+        }
+    }
+}
+
+impl<DB, T> QueryFragment<DB> for CollectedQuery<T>
+where
+    DB: Backend + DieselReserveSpecialization,
+    for<'a> <DB as Backend>::BindCollector<'a>: MoveableBindCollector<DB, BindData = T>,
+{
+    fn walk_ast<'b>(&'b self, mut pass: AstPass<'_, 'b, DB>) -> QueryResult<()> {
+        if !self.safe_to_cache_prepared {
+            pass.unsafe_to_cache_prepared();
+        }
+        pass.push_sql(&self.sql);
+        pass.push_bind_collector_data::<T>(&self.bind_data)
+    }
+}
+
+impl<T> QueryId for CollectedQuery<T> {
+    type QueryId = ();
+
+    const HAS_STATIC_QUERY_ID: bool = false;
+}
+
+impl<T> Query for CollectedQuery<T> {
+    type SqlType = Untyped;
+}

diesel/src/query_builder/mod.rs

@@ -11,6 +11,7 @@ mod clause_macro;
 
 pub(crate) mod ast_pass;
 pub mod bind_collector;
+mod collected_query;
 pub(crate) mod combination_clause;
 mod debug_query;
 mod delete_statement;
@@ -37,7 +38,9 @@ pub(crate) mod where_clause;
 #[doc(inline)]
 pub use self::ast_pass::AstPass;
 #[doc(inline)]
-pub use self::bind_collector::BindCollector;
+pub use self::bind_collector::{BindCollector, MoveableBindCollector};
+#[doc(inline)]
+pub use self::collected_query::CollectedQuery;
 #[doc(inline)]
 pub use self::debug_query::DebugQuery;
 #[doc(inline)]

diesel/src/row.rs

@@ -148,6 +148,18 @@ where
     }
 }
 
+/// A row that can be turned into an owned version
+#[diesel_derives::__diesel_public_if(
+    feature = "i-implement-a-third-party-backend-and-opt-into-breaking-changes"
+)]
+pub trait IntoOwnedRow<'a, DB: Backend>: Row<'a, DB> {
+    /// The owned version of the row
+    type OwnedRow: Row<'a, DB> + Send + 'static;
+
+    /// Turn the row into its owned version
+    fn into_owned(self) -> Self::OwnedRow;
+}
+
 // These traits are not part of the public API
 // because:
 // * we want to control who can implement `Row` (for `RowSealed`)

diesel/src/sqlite/connection/bind_collector.rs

@@ -1,4 +1,4 @@
-use crate::query_builder::BindCollector;
+use crate::query_builder::{BindCollector, MoveableBindCollector};
 use crate::serialize::{IsNull, Output};
 use crate::sql_types::HasSqlType;
 use crate::sqlite::{Sqlite, SqliteType};
@@ -200,3 +200,76 @@ impl<'a> BindCollector<'a, Sqlite> for SqliteBindCollector<'a> {
         Ok(())
     }
 }
+
+#[derive(Debug)]
+enum OwnedSqliteBindValue {
+    String(Box<str>),
+    Binary(Box<[u8]>),
+    I32(i32),
+    I64(i64),
+    F64(f64),
+    Null,
+}
+
+impl<'a> std::convert::From<&InternalSqliteBindValue<'a>> for OwnedSqliteBindValue {
+    fn from(value: &InternalSqliteBindValue<'a>) -> Self {
+        match value {
+            InternalSqliteBindValue::String(s) => Self::String(s.clone()),
+            InternalSqliteBindValue::BorrowedString(s) => {
+                Self::String(String::from(*s).into_boxed_str())
+            }
+            InternalSqliteBindValue::Binary(b) => Self::Binary(b.clone()),
+            InternalSqliteBindValue::BorrowedBinary(s) => {
+                Self::Binary(Vec::from(*s).into_boxed_slice())
+            }
+            InternalSqliteBindValue::I32(val) => Self::I32(*val),
+            InternalSqliteBindValue::I64(val) => Self::I64(*val),
+            InternalSqliteBindValue::F64(val) => Self::F64(*val),
+            InternalSqliteBindValue::Null => Self::Null,
+        }
+    }
+}
+
+impl<'a> std::convert::From<&OwnedSqliteBindValue> for InternalSqliteBindValue<'a> {
+    fn from(value: &OwnedSqliteBindValue) -> Self {
+        match value {
+            OwnedSqliteBindValue::String(s) => Self::String(s.clone()),
+            OwnedSqliteBindValue::Binary(b) => Self::Binary(b.clone()),
+            OwnedSqliteBindValue::I32(val) => Self::I32(*val),
+            OwnedSqliteBindValue::I64(val) => Self::I64(*val),
+            OwnedSqliteBindValue::F64(val) => Self::F64(*val),
+            OwnedSqliteBindValue::Null => Self::Null,
+        }
+    }
+}
+
+#[derive(Debug)]
+/// Sqlite bind collector data that is movable across threads
+pub struct SqliteBindCollectorData {
+    binds: Vec<(OwnedSqliteBindValue, SqliteType)>,
+}
+
+impl MoveableBindCollector<Sqlite> for SqliteBindCollector<'_> {
+    type BindData = SqliteBindCollectorData;
+
+    fn moveable(&self) -> Self::BindData {
+        let mut binds = Vec::with_capacity(self.binds.len());
+        for b in self
+            .binds
+            .iter()
+            .map(|(bind, tpe)| (OwnedSqliteBindValue::from(bind), *tpe))
+        {
+            binds.push(b);
+        }
+        SqliteBindCollectorData { binds }
+    }
+
+    fn append_bind_data(&mut self, from: &Self::BindData) {
+        self.binds.reserve_exact(from.binds.len());
+        self.binds.extend(
+            from.binds
+                .iter()
+                .map(|(bind, tpe)| (InternalSqliteBindValue::from(bind), *tpe)),
+        );
+    }
+}

diesel/src/sqlite/connection/mod.rs

@@ -2,6 +2,7 @@ extern crate libsqlite3_sys as ffi;
 
 mod bind_collector;
 mod functions;
+mod owned_row;
 mod raw;
 mod row;
 mod serialized_database;
@@ -28,7 +29,7 @@ use crate::expression::QueryMetadata;
 use crate::query_builder::*;
 use crate::result::*;
 use crate::serialize::ToSql;
-use crate::sql_types::HasSqlType;
+use crate::sql_types::{HasSqlType, TypeMetadata};
 use crate::sqlite::Sqlite;
 
 /// Connections for the SQLite backend. Unlike other backends, SQLite supported
@@ -123,6 +124,9 @@ pub struct SqliteConnection {
     statement_cache: StatementCache<Sqlite, Statement>,
     raw_connection: RawConnection,
     transaction_state: AnsiTransactionManager,
+    // this exists for the sole purpose of implementing `WithMetadataLookup` trait
+    // and avoiding static mut which will be deprecated in 2024 edition
+    metadata_lookup: (),
     instrumentation: Option<Box<dyn Instrumentation>>,
 }
 
@@ -220,6 +224,12 @@ impl LoadConnection<DefaultLoadingMode> for SqliteConnection {
     }
 }
 
+impl WithMetadataLookup for SqliteConnection {
+    fn metadata_lookup(&mut self) -> &mut <Sqlite as TypeMetadata>::MetadataLookup {
+        &mut self.metadata_lookup
+    }
+}
+
 #[cfg(feature = "r2d2")]
 impl crate::r2d2::R2D2Connection for crate::sqlite::SqliteConnection {
     fn ping(&mut self) -> QueryResult<()> {
@@ -529,6 +539,7 @@ impl SqliteConnection {
             statement_cache: StatementCache::new(),
             raw_connection,
             transaction_state: AnsiTransactionManager::default(),
+            metadata_lookup: (),
             instrumentation: None,
         };
         conn.register_diesel_sql_functions()