You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: aggregate_exchange_injector.rs
    path of file: ./repos/databend/src/query/service/src/pipelines/processors/transforms/aggregator
    
    the code of the file until where you have to start completion: // Copyright 2021 Datafuse Labs
//
// 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::marker::PhantomData;
use std::sync::Arc;

use bumpalo::Bump;
use databend_common_catalog::table_context::TableContext;
use databend_common_exception::ErrorCode;
use databend_common_exception::Result;
use databend_common_expression::BlockMetaInfoDowncast;
use databend_common_expression::DataBlock;
use databend_common_expression::Payload;
use databend_common_expression::PayloadFlushState;
    
    fn execute(&self, mut data_block: DataBlock) -> Result<Vec<DataBlock>> {
        if let Some(block_meta) = data_block.take_meta() {
            if let Some(block_meta) = AggregateMeta::<Method, V>::downcast_from(block_meta) {
                let mut blocks = Vec::with_capacity(self.buckets);
                match block_meta {
                    AggregateMeta::Spilled(_) => unreachable!(),
                    AggregateMeta::BucketSpilled(_) => unreachable!(),
                    AggregateMeta::Serialized(_) => unreachable!(),
                    AggregateMeta::Partitioned { .. } => unreachable!(),
                    AggregateMeta::Spilling(payload) => {
                        let method = PartitionedHashMethod::create(self.method.clone());
                        for hashtable_cell in scatter(payload, self.buckets, &method)? {
                            blocks.push(match hashtable_cell.hashtable.len() == 0 {
                                true => DataBlock::empty(),
                                false => DataBlock::empty_with_meta(
                                    AggregateMeta::<Method, V>::create_spilling(hashtable_cell),
                                ),
                            });
                        }
                    }
                    AggregateMeta::HashTable(payload) => {
                        let bucket = payload.bucket;
                        for hashtable_cell in scatter(payload, self.buckets, &self.method)? {
                            blocks.push(match hashtable_cell.hashtable.len() == 0 {
                                true => DataBlock::empty(),
                                false => DataBlock::empty_with_meta(
                                    AggregateMeta::<Method, V>::create_hashtable(
                                        bucket,
                                        hashtable_cell,
                                    ),
                                ),
                            });
                        }
                    }
                    AggregateMeta::AggregateHashTable(_) => unreachable!(),
                    AggregateMeta::AggregatePayload(p) => {
                        for payload in scatter_paylaod(p.payload, self.buckets)? {
                            blocks.push(DataBlock::empty_with_meta(
                                AggregateMeta::<Method, V>::create_agg_payload(
                                    p.bucket,
                                    payload,
                                    p.max_partition_count,
                                ),
                            ))
                        }
                    }
                };

                return Ok(blocks);
            }
        }

        Err(ErrorCode::Internal(
            "Internal, HashTableHashScatter only recv AggregateMeta",
        ))
    }