timsaucer commented on code in PR #24028: URL: https://github.com/apache/datafusion/pull/24028#discussion_r3712459895
########## datafusion/ffi/src/query_planner.rs: ########## @@ -0,0 +1,402 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +//! FFI support for [`QueryPlanner`]. +//! +//! A typical deployment has three libraries. Library A (for example, +//! `datafusion-python`) owns the [`Session`] and codec registry. Library B owns +//! a custom table provider and its extension nodes. Library C (for example, +//! Ballista or `datafusion-distributed`) owns the query planner. A serializes a +//! logical plan and invokes C, while `FFI_SessionRef` lets C call session +//! services in A. C deserializes the logical plan, creates a physical plan, +//! serializes that result, and returns it for A to deserialize. The logical and +//! physical extension codecs preserve nodes supplied by B. +//! +//! The physical result is serialized instead of returned as an +//! [`crate::execution_plan::FFI_ExecutionPlan`]. An FFI execution-plan handle is +//! a foreign trait-object proxy, so even a built-in plan created in C cannot be +//! downcast to its concrete +//! type in A. Serialization reconstructs known plan nodes with A's local Rust +//! type identities, allowing A's optimizers and other consumers to downcast +//! them. Extension codecs control how custom nodes are reconstructed. +//! +//! A node returned by B while C is planning is still foreign to C unless a +//! codec boundary reconstructs it in C. The query-planner boundary guarantees +//! that C-local serializable nodes, and extension nodes understood by the +//! configured codecs, are reconstructed for A when the completed plan returns. + +use std::ffi::c_void; +use std::sync::Arc; + +use async_ffi::{FfiFuture, FutureExt}; +use async_trait::async_trait; +use datafusion_common::error::{DataFusionError, Result}; +use datafusion_expr::LogicalPlan; +use datafusion_physical_plan::ExecutionPlan; +use datafusion_proto::bytes::{ + logical_plan_from_bytes_with_extension_codec, + logical_plan_to_bytes_with_extension_codec, + physical_plan_from_bytes_with_extension_codec, + physical_plan_to_bytes_with_extension_codec, +}; +use datafusion_proto::logical_plan::{ + DefaultLogicalExtensionCodec, LogicalExtensionCodec, +}; +use datafusion_proto::physical_plan::{ + DefaultPhysicalExtensionCodec, PhysicalExtensionCodec, +}; +use datafusion_session::{QueryPlanner, Session}; +use stabby::vec::Vec as SVec; +use tokio::runtime::Handle; + +use crate::execution::FFI_TaskContextProvider; +use crate::proto::logical_extension_codec::FFI_LogicalExtensionCodec; +use crate::proto::physical_extension_codec::FFI_PhysicalExtensionCodec; +use crate::session::{FFI_SessionRef, ForeignSession}; +use crate::util::FFI_Result; +use crate::{df_result, sresult_return}; + +/// An ABI-stable handle to a [`QueryPlanner`] owned by another library. +/// +/// The Rust-facing adapters serialize the input [`LogicalPlan`] and resulting +/// [`ExecutionPlan`]; callers do not invoke the byte-oriented function pointer +/// directly. +#[repr(C)] +#[derive(Debug)] +pub struct FFI_QueryPlanner { + create_physical_plan: unsafe extern "C" fn( + &Self, + logical_plan_serialized: SVec<u8>, + session: FFI_SessionRef, + ) -> FfiFuture<FFI_Result<SVec<u8>>>, Review Comment: The reason for this is the case that is illustrated in the integration test `test_three_library_query_planner_restores_type_identity`. Suppose we want one query planner to call another. Each of these planners tend to rely on downcasting the execution plans. By making the FFI query planner calls return the serialized plans, then it gets decoded within each library locally. By doing this we should get local versions of the well known execution plans that the default codec can provide. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
