diff --git a/sqlx-core/src/database.rs b/sqlx-core/src/database.rs
index 79c67445..70dea800 100644
--- a/sqlx-core/src/database.rs
+++ b/sqlx-core/src/database.rs
@@ -28,6 +28,8 @@ where
 
     /// The Rust type of table identifiers for this database.
     type TableId: Display + Clone;
+
+    type RawBuffer;
 }
 
 pub trait HasRawValue<'c> {
diff --git a/sqlx-core/src/mysql/database.rs b/sqlx-core/src/mysql/database.rs
index 62a22898..e2233bbf 100644
--- a/sqlx-core/src/mysql/database.rs
+++ b/sqlx-core/src/mysql/database.rs
@@ -11,6 +11,8 @@ impl Database for MySql {
     type TypeInfo = super::MySqlTypeInfo;
 
     type TableId = Box<str>;
+
+    type RawBuffer = Vec<u8>;
 }
 
 impl<'c> HasRow<'c> for MySql {
diff --git a/sqlx-core/src/postgres/database.rs b/sqlx-core/src/postgres/database.rs
index 5792f464..399b2f67 100644
--- a/sqlx-core/src/postgres/database.rs
+++ b/sqlx-core/src/postgres/database.rs
@@ -12,6 +12,8 @@ impl Database for Postgres {
     type TypeInfo = super::PgTypeInfo;
 
     type TableId = u32;
+
+    type RawBuffer = Vec<u8>;
 }
 
 impl<'a> HasRow<'a> for Postgres {