rkrishn7 commented on code in PR #17529: URL: https://github.com/apache/datafusion/pull/17529#discussion_r2353807675
########## datafusion/physical-plan/src/joins/hash_join/information_passing.rs: ########## @@ -0,0 +1,612 @@ +// 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. + +//! Utilities for passing information from the build side of a hash join to the probe side. +//! This is also known as "sideways information passing", and enables optimizations that take +//! of the smaller build side to reduce data processed on the larger probe side. +//! +//! As an example, let's consider TPC-H Query 17: +//! +//! ```sql +//! select +//! sum(l_extendedprice) / 7.0 as avg_yearly +//! from +//! lineitem, +//! part +//! where +//! p_partkey = l_partkey +//! and p_brand = 'Brand#23' +//! and p_container = 'MED BOX' +//! and l_quantity < ( +//! select +//! 0.2 * avg(l_quantity) +//! from +//! lineitem +//! where +//! l_partkey = p_partkey +//! ); +//! ``` +//! The join portion of the query should look something like this: +//! +//! ```text Review Comment: Thanks @alamb for the diagrams 😄 (from https://github.com/apache/datafusion/issues/7955) -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
