jvanstraten commented on a change in pull request #12279: URL: https://github.com/apache/arrow/pull/12279#discussion_r796530895
########## File path: cpp/examples/arrow/engine_substrait_consumption.cc ########## @@ -0,0 +1,187 @@ +// 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. + +#include <arrow/api.h> +#include <arrow/compute/api.h> +#include <arrow/compute/exec/options.h> +#include <arrow/engine/substrait/serde.h> + +#include <cstdlib> +#include <iostream> +#include <memory> +#include <vector> + +namespace eng = ::arrow::engine; +namespace cp = ::arrow::compute; + +#define ABORT_ON_FAILURE(expr) \ + do { \ + arrow::Status status_ = (expr); \ + if (!status_.ok()) { \ + std::cerr << status_.message() << std::endl; \ + abort(); \ + } \ + } while (0); + +arrow::Future<std::shared_ptr<arrow::Buffer>> GetSubstraitFromServer(); + +class IgnoringConsumer : public cp::SinkNodeConsumer { + public: + explicit IgnoringConsumer(size_t tag) : tag_{tag} {} + + arrow::Status Consume(cp::ExecBatch batch) override { + // Consume a batch of data + // (just print its row count to stdout) + std::cout << "-" << tag_ << " consumed " << batch.length << " rows" << std::endl; + return arrow::Status::OK(); + } + + arrow::Future<> Finish() override { + // Signal to the consumer that the last batch has been delivered + // (we don't do any real work in this consumer so mark it finished immediately) + // + // The returned future should only finish when all outstanding tasks have completed + // (after this method is called Consume is guaranteed not to be called again) + std::cout << "-" << tag_ << " finished" << std::endl; + return arrow::Future<>::MakeFinished(); + } + + private: + size_t tag_; +}; + +int main(int argc, char** argv) { + // Plans arrive at the consumer serialized in a substrait-formatted Buffer + auto maybe_serialized_plan = GetSubstraitFromServer().result(); + ABORT_ON_FAILURE(maybe_serialized_plan.status()); + std::shared_ptr<arrow::Buffer> serialized_plan = + std::move(maybe_serialized_plan).ValueOrDie(); + + // Print the received plan to stdout as JSON + arrow::Result<std::string> maybe_plan_json = + eng::internal::SubstraitToJSON("Plan", *serialized_plan); + ABORT_ON_FAILURE(maybe_plan_json.status()); + std::cout << std::string('#', 50) << " received substrait::Plan:" << std::endl; + std::cout << maybe_plan_json.ValueOrDie() << std::endl; + + // Deserializing a plan requires a factory for consumers: each time a sink node is + // deserialized, a consumer is constructed into which its batches will be piped. + std::vector<std::shared_ptr<cp::SinkNodeConsumer>> consumers; + std::function<std::shared_ptr<cp::SinkNodeConsumer>()> consumer_factory = [&] { + // All batches produced by the plan will be fed into IgnoringConsumers: + auto tag = consumers.size(); + consumers.emplace_back(new IgnoringConsumer{tag}); + return consumers.back(); + }; + + // NOTE Although most of the Deserialize functions require a const ExtensionSet& to + // resolve extension references, a Plan is what we use to construct that ExtensionSet. + // (It should be an optional output later.) In particular, it does not need to be kept + // alive nor does the serialized plan- none of the arrow:: objects in the output will + // contain references to memory owned by either. + auto maybe_decls = eng::DeserializePlan(*serialized_plan, consumer_factory); + ABORT_ON_FAILURE(maybe_decls.status()); + std::vector<cp::Declaration> decls = std::move(maybe_decls).ValueOrDie(); + + // It's safe to drop the serialized plan; we don't leave references to its memory + serialized_plan.reset(); + + // Construct an empty plan (note: configure Function registry and ThreadPool here) + auto maybe_plan = cp::ExecPlan::Make(); + ABORT_ON_FAILURE(maybe_plan.status()); + std::shared_ptr<cp::ExecPlan> plan = std::move(maybe_plan).ValueOrDie(); + + for (const cp::Declaration& decl : decls) { + // Add decl to plan (note: configure ExecNode registry here) + ABORT_ON_FAILURE(decl.AddToPlan(plan.get()).status()); + } + + // Validate the plan and print it to stdout + ABORT_ON_FAILURE(plan->Validate()); + std::cout << std::string('#', 50) << " produced arrow::ExecPlan:" << std::endl; + std::cout << plan->ToString() << std::endl; + + // Start the plan... + std::cout << std::string('#', 50) << " consuming batches:" << std::endl; + ABORT_ON_FAILURE(plan->StartProducing()); + + // ... and wait for it to finish + ABORT_ON_FAILURE(plan->finished().status()); + return EXIT_SUCCESS; +} + +arrow::Future<std::shared_ptr<arrow::Buffer>> GetSubstraitFromServer() { + // Emulate server interaction by parsing hard coded JSON + return eng::internal::SubstraitFromJSON("Plan", R"({ + "relations": [ + {"rel": { + "read": { + "base_schema": { + "struct": { + "types": [ {"i64": {}}, {"bool": {}} ] + }, + "names": ["i", "b"] + }, + "filter": { + "selection": { + "directReference": { + "structField": { + "field": 1 + } + } + } + }, + "local_files": { + "items": [ + { + "uri_file": "file:///tmp/dat1.parquet", + "format": "FILE_FORMAT_PARQUET" + }, + { + "uri_file": "file:///tmp/dat2.parquet", + "format": "FILE_FORMAT_PARQUET" + } + ] + } + } + }} + ], + "extension_uris": [ + { + "extension_uri_anchor": 7, + "uri": "https://github.com/apache/arrow/blob/master/format/substrait/extension_types.yaml"; + } + ], + "extensions": [ + {"extension_type": { + "extension_uri_reference": 7, + "type_anchor": 42, + "name": "null" + }}, + {"extension_type_variation": { + "extension_uri_reference": 7, + "type_variation_anchor": 23, + "name": "u8" + }}, + {"extension_function": { + "extension_uri_reference": 7, + "function_anchor": 42, + "name": "add" + }} + ] Review comment: I think they're just there as examples of how you would define types and functions once you make a plan that actually does something useful, without making the plan as a whole unnecessarily verbose. IMO, the target audience for the contents of this plan are people who either already have in-depth knowledge of the Substrait spec or are interested in obtaining it. Users who just get the plan from some other framework should understand from the comment in the function and the context its used in that this is just a mockup of that other framework, so they don't need to understand what it does. -- 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: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
