adriangb commented on code in PR #15566: URL: https://github.com/apache/datafusion/pull/15566#discussion_r2049207122
########## datafusion/physical-optimizer/src/push_down_filter.rs: ########## @@ -0,0 +1,535 @@ +// 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. + +use std::sync::Arc; + +use crate::PhysicalOptimizerRule; + +use datafusion_common::tree_node::{Transformed, TreeNode, TreeNodeRecursion}; +use datafusion_common::{config::ConfigOptions, Result}; +use datafusion_physical_expr::conjunction; +use datafusion_physical_plan::filter::FilterExec; +use datafusion_physical_plan::filter_pushdown::{ + FilterDescription, FilterPushdownResult, FilterPushdownSupport, +}; +use datafusion_physical_plan::tree_node::PlanContext; +use datafusion_physical_plan::ExecutionPlan; + +/// Attempts to recursively push given filters from the top of the tree into leafs. +/// +/// # Default Implementation +/// +/// The default implementation in [`ExecutionPlan::try_pushdown_filters`] is a no-op +/// that assumes that: +/// +/// * Parent filters can't be passed onto children. +/// * This node has no filters to contribute. +/// +/// # Example: Push filter into a `DataSourceExec` +/// +/// For example, consider the following plan: +/// +/// ```text +/// ┌──────────────────────┐ +/// │ CoalesceBatchesExec │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ FilterExec │ +/// │ filters = [ id=1] │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ DataSourceExec │ +/// │ projection = * │ +/// └──────────────────────┘ +/// ``` +/// +/// Our goal is to move the `id = 1` filter from the [`FilterExec`] node to the `DataSourceExec` node. +/// +/// If this filter is selective pushing it into the scan can avoid massive +/// amounts of data being read from the source (the projection is `*` so all +/// matching columns are read). +/// +/// The new plan looks like: +/// +/// ```text +/// ┌──────────────────────┐ +/// │ CoalesceBatchesExec │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ DataSourceExec │ +/// │ projection = * │ +/// │ filters = [ id=1] │ +/// └──────────────────────┘ +/// ``` +/// +/// # Example: Push filters with `ProjectionExec` +/// +/// Let's consider a more complex example involving a [`ProjectionExec`] +/// node in between the [`FilterExec`] and `DataSourceExec` nodes that +/// creates a new column that the filter depends on. +/// +/// ```text +/// ┌──────────────────────┐ +/// │ CoalesceBatchesExec │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ FilterExec │ +/// │ filters = │ +/// │ [cost>50,id=1] │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ ProjectionExec │ +/// │ cost = price * 1.2 │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ DataSourceExec │ +/// │ projection = * │ +/// └──────────────────────┘ +/// ``` +/// +/// We want to push down the filters `[id=1]` to the `DataSourceExec` node, +/// but can't push down `cost>50` because it requires the [`ProjectionExec`] +/// node to be executed first. A simple thing to do would be to split up the +/// filter into two separate filters and push down the first one: +/// +/// ```text +/// ┌──────────────────────┐ +/// │ CoalesceBatchesExec │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ FilterExec │ +/// │ filters = │ +/// │ [cost>50] │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ ProjectionExec │ +/// │ cost = price * 1.2 │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ DataSourceExec │ +/// │ projection = * │ +/// │ filters = [ id=1] │ +/// └──────────────────────┘ +/// ``` +/// +/// We can actually however do better by pushing down `price * 1.2 > 50` +/// instead of `cost > 50`: +/// +/// ```text +/// ┌──────────────────────┐ +/// │ CoalesceBatchesExec │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ ProjectionExec │ +/// │ cost = price * 1.2 │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ DataSourceExec │ +/// │ projection = * │ +/// │ filters = [id=1, │ +/// │ price * 1.2 > 50] │ +/// └──────────────────────┘ +/// ``` +/// +/// # Example: Push filters within a subtree +/// +/// There are also cases where we may be able to push down filters within a +/// subtree but not the entire tree. A good example of this is aggregation +/// nodes: +/// +/// ```text +/// ┌──────────────────────┐ +/// │ ProjectionExec │ +/// │ projection = * │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ FilterExec │ +/// │ filters = [sum > 10] │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌───────────────────────┐ +/// │ AggregateExec │ +/// │ group by = [id] │ +/// │ aggregate = │ +/// │ [sum(price)] │ +/// └───────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ FilterExec │ +/// │ filters = [id=1] │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ +/// │ DataSourceExec │ +/// │ projection = * │ +/// └──────────────────────┘ +/// ``` +/// +/// The transformation here is to push down the `id=1` filter to the +/// `DataSourceExec` node: +/// +/// ```text +/// ┌──────────────────────┐ +/// │ ProjectionExec │ +/// │ projection = * │ +/// └──────────────────────┘ +/// │ +/// ▼ +/// ┌──────────────────────┐ Review Comment: Sorry I missed it. Why does it need an update, did we change how this behaves? -- 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...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
