columnar: support bucket parallel read in region

contrib/tiflash-columnar-hub/hub-runtime/ffi/src/RaftStoreProxyFFI/ProxyFFI.h

@@ -228,6 +228,8 @@ struct SSTReaderInterfaces {
 struct CloudStorageEngineInterfaces {
   bool (*fn_get_keyspace_encryption)(RaftStoreProxyPtr, uint32_t);
   RawCppStringPtr (*fn_get_master_key)(RaftStoreProxyPtr);
+  RustStrWithViewVec (*fn_get_region_bucket_keys)(uint64_t, uint64_t,
+                                                  RaftStoreProxyPtr);
   ColumnarReaderPtr (*fn_get_columnar_reader)(uint64_t, uint64_t, uint64_t,
                                               BaseBuffView, BaseBuffView,
                                               BaseBuffView, BaseBuffView,

contrib/tiflash-columnar-hub/hub-runtime/src/cloud_helper.rs

@@ -176,6 +176,16 @@ impl PdClientWithCache {
     pub fn get_security_mgr(&self) -> Arc<SecurityManager> {
         self.pd_client.get_security_mgr()
     }
+
+    pub fn get_region_bucket_keys(&self, region_id: u64, region_ver: u64) -> Vec<Vec<u8>> {
+        let Some(bucket_stat) = self.pd_client.get_buckets(region_id) else {
+            return Vec::new();
+        };
+        if bucket_stat.meta.region_epoch.get_version() != region_ver {
+            return Vec::new();
+        }
+        bucket_stat.meta.keys.clone()
+    }
 }
 
 #[derive(Clone)]
@@ -444,6 +454,10 @@ impl CloudHelper {
             }
         }
     }
+
+    pub fn get_region_bucket_keys(&self, region_id: u64, region_ver: u64) -> Vec<Vec<u8>> {
+        self.pd_client.get_region_bucket_keys(region_id, region_ver)
+    }
 }
 
 fn collect_ia_meta_files(meta_paths: &[PathBuf]) -> std::io::Result<Vec<IaMetaFileEntry>> {

contrib/tiflash-columnar-hub/hub-runtime/src/columnar_impls.rs

@@ -18,10 +18,10 @@ use kvengine::{CloudColumnarReaders, TableCtx};
 use protobuf::{parse_from_bytes, Message};
 
 use crate::{
-    build_from_string,
+    build_from_string, build_from_vec_string,
     interfaces_ffi::{
         BaseBuffView, ColumnarReaderErrorType, ColumnarReaderPtr, RaftStoreProxyPtr, RawRustPtr,
-        RawVoidPtr, RustStrWithView,
+        RawVoidPtr, RustStrWithView, RustStrWithViewVec,
     },
     RawRustPtrType,
 };
@@ -73,6 +73,22 @@ impl From<crate::Error> for ColumnarReaderPtr {
     }
 }
 
+pub unsafe extern "C" fn ffi_get_region_bucket_keys(
+    region_id: u64,
+    region_ver: u64,
+    hub_ptr: RaftStoreProxyPtr,
+) -> RustStrWithViewVec {
+    let hub = hub_ptr.as_ref();
+    let bucket_keys = hub
+        .cloud_helper
+        .get_region_bucket_keys(region_id, region_ver);
+    if bucket_keys.is_empty() {
+        RustStrWithViewVec::default()
+    } else {
+        build_from_vec_string(bucket_keys)
+    }
+}
+
 pub unsafe extern "C" fn ffi_make_columnar_reader(
     shard_id: u64,
     shard_ver: u64,

contrib/tiflash-columnar-hub/hub-runtime/src/interfaces.rs

@@ -355,6 +355,13 @@ pub mod root {
                     arg1: root::DB::RaftStoreProxyPtr,
                 ) -> root::DB::RawCppStringPtr,
             >,
+            pub fn_get_region_bucket_keys: ::std::option::Option<
+                unsafe extern "C" fn(
+                    arg1: u64,
+                    arg2: u64,
+                    arg3: root::DB::RaftStoreProxyPtr,
+                ) -> root::DB::RustStrWithViewVec,
+            >,
             pub fn_get_columnar_reader: ::std::option::Option<
                 unsafe extern "C" fn(
                     arg1: u64,

contrib/tiflash-columnar-hub/hub-runtime/src/run.rs

@@ -55,8 +55,8 @@ use tikv_util::{
 use crate::{
     cloud_helper::{CloudEngineBackends, CloudHelper},
     columnar_impls::{
-        ffi_make_columnar_reader, ffi_physical_table_id, ffi_read_block, ffi_read_column,
-        ffi_read_handle, ffi_read_version,
+        ffi_get_region_bucket_keys, ffi_make_columnar_reader, ffi_physical_table_id,
+        ffi_read_block, ffi_read_column, ffi_read_handle, ffi_read_version,
     },
     domain_impls::ffi_gc_rust_ptr,
     engine_store_helper::{
@@ -1140,6 +1140,7 @@ fn build_hub_ffi_helper(hub: &ColumnarHub) -> RaftStoreProxyFFIHelper {
         cloud_storage_engine_interfaces: CloudStorageEngineInterfaces {
             fn_get_keyspace_encryption: Some(ffi_get_keyspace_encryption),
             fn_get_master_key: Some(ffi_get_master_key),
+            fn_get_region_bucket_keys: Some(ffi_get_region_bucket_keys),
             fn_get_columnar_reader: Some(ffi_make_columnar_reader),
             fn_read_block: Some(ffi_read_block),
             fn_read_handle: Some(ffi_read_handle),