rows_result: implement into_inner behind cpp_rust_unstable cfg

This is convenience introduced only for cpp-rust-driver purposes.

We will use DeserializedMetadataAndRawRows directly to implement
lazy deserialization in cpp-rust-driver

scylla/Cargo.toml

@@ -98,4 +98,8 @@ harness = false
 [lints.rust]
 unnameable_types = "warn"
 unreachable_pub = "warn"
-unexpected_cfgs = { level = "warn", check-cfg = ['cfg(scylla_cloud_tests)', 'cfg(cassandra_tests)'] }
+unexpected_cfgs = { level = "warn", check-cfg = [
+    'cfg(scylla_cloud_tests)',
+    'cfg(cassandra_tests)',
+    'cfg(cpp_rust_unstable)',
+] }

scylla/src/lib.rs

@@ -118,6 +118,9 @@ pub mod frame {
         pub(crate) use scylla_cql::frame::response::*;
 
         pub mod result {
+            #[cfg(cpp_rust_unstable)]
+            pub use scylla_cql::frame::response::result::DeserializedMetadataAndRawRows;
+
             pub(crate) use scylla_cql::frame::response::result::*;
             pub use scylla_cql::frame::response::result::{
                 ColumnSpec, ColumnType, CqlValue, PartitionKeyIndex, Row, TableSpec,

scylla/src/transport/query_result.rs

@@ -433,6 +433,17 @@ impl QueryRowsResult {
             Err(RowsError::TypeCheckFailed(err)) => Err(SingleRowError::TypeCheckFailed(err)),
         }
     }
+
+    #[cfg(cpp_rust_unstable)]
+    pub fn into_inner(self) -> (DeserializedMetadataAndRawRows, Option<Uuid>, Vec<String>) {
+        let Self {
+            raw_rows_with_metadata,
+            tracing_id,
+            warnings,
+        } = self;
+
+        (raw_rows_with_metadata, tracing_id, warnings)
+    }
 }
 
 /// An error returned by [`QueryResult::into_rows_result`]