feat: define prepared batch submission interface

Signed-off-by: WenyXu <wenymedia@gmail.com>

src/operator/src/batcher.rs

@@ -0,0 +1,41 @@
+// Copyright 2023 Greptime Team
+//
+// Licensed 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.
+
+use std::sync::Arc;
+
+use arrow::record_batch::RecordBatch;
+use async_trait::async_trait;
+use session::context::QueryContextRef;
+use table::metadata::TableInfoRef;
+use tokio::sync::OwnedSemaphorePermit;
+
+use crate::error::Result;
+
+/// Accepts prepared table writes without coupling the inserter to a batcher implementation.
+/// Schema creation, alteration and default evaluation remain the caller's responsibility.
+#[async_trait]
+pub trait PendingRowsBatcher: Send + Sync {
+    /// Acquires one slot per original request, shared by all of its table submissions.
+    async fn acquire(&self) -> Result<Arc<OwnedSemaphorePermit>>;
+
+    /// Waits for the submitted rows to be written, retaining the slot through completion.
+    /// Cancelling the response wait does not retract an already enqueued submission.
+    async fn submit(
+        &self,
+        table_info: TableInfoRef,
+        batch: RecordBatch,
+        ctx: QueryContextRef,
+        permit: Arc<OwnedSemaphorePermit>,
+    ) -> Result<usize>;
+}

src/operator/src/lib.rs

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+pub mod batcher;
 mod bulk_insert;
 pub mod delete;
 pub mod error;