Method distributedWrite

src/Storages/StorageDistributed.cpp:763–841

QueryPipelinePtr StorageDistributed::distributedWrite(const ASTInsertQuery & query, ContextPtr local_context)
{
    const Settings & settings = local_context->getSettingsRef();
    std::shared_ptr<StorageDistributed> storage_src;
    auto & select = query.select->as<ASTSelectWithUnionQuery &>();
    auto new_query = std::dynamic_pointer_cast<ASTInsertQuery>(query.clone());
    if (select.list_of_selects->children.size() == 1)
    {
        if (auto * select_query = select.list_of_selects->children.at(0)->as<ASTSelectQuery>())
        {
            JoinedTables joined_tables(Context::createCopy(local_context), *select_query);

            if (joined_tables.tablesCount() == 1)
            {
                storage_src = std::dynamic_pointer_cast<StorageDistributed>(joined_tables.getLeftTableStorage());
                if (storage_src)
                {
                    const auto select_with_union_query = std::make_shared<ASTSelectWithUnionQuery>();
                    select_with_union_query->list_of_selects = std::make_shared<ASTExpressionList>();

                    auto new_select_query = std::dynamic_pointer_cast<ASTSelectQuery>(select_query->clone());
                    select_with_union_query->list_of_selects->children.push_back(new_select_query);

                    new_select_query->replaceDatabaseAndTable(storage_src->getRemoteDatabaseName(), storage_src->getRemoteTableName());

                    new_query->select = select_with_union_query;
                }
            }
        }
    }

    if (!storage_src || storage_src->getClusterName() != getClusterName())
    {
        return nullptr;
    }

    if (settings.parallel_distributed_insert_select == PARALLEL_DISTRIBUTED_INSERT_SELECT_ALL
        || settings.distributed_perfect_shard)
    {
        new_query->table_id = StorageID(getRemoteDatabaseName(), getRemoteTableName());
    }

    const auto & cluster = getCluster();
    const auto & shards_info = cluster->getShardsInfo();

    std::vector<std::unique_ptr<QueryPipeline>> pipelines;

    String new_query_str = queryToString(new_query);
    LOG_TRACE(log, "Parallel insert query: {}", new_query_str);

    for (size_t shard_index : collections::range(0, shards_info.size()))
    {
        const auto & shard_info = shards_info[shard_index];
        if (shard_info.isLocal())
        {
            InterpreterInsertQuery interpreter(new_query, local_context);
            pipelines.emplace_back(std::make_unique<QueryPipeline>(interpreter.execute().pipeline));
        }