alamb commented on code in PR #14595: URL: https://github.com/apache/datafusion/pull/14595#discussion_r1953460041
########## datafusion/optimizer/src/decorrelate_lateral_join.rs: ########## @@ -0,0 +1,106 @@ +// 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. + +//! [`DecorrelateLateralJoin`] decorrelates logical plans produced by lateral joins. + +use crate::optimizer::ApplyOrder; +use crate::{decorrelate_predicate_subquery, OptimizerConfig, OptimizerRule}; + +use datafusion_common::tree_node::{Transformed, TreeNodeRecursion, TreeNodeVisitor}; +use datafusion_common::Result; +use datafusion_expr::logical_plan::JoinType; +use datafusion_expr::LogicalPlan; + +/// Optimizer rule for rewriting lateral joins to joins +#[derive(Default, Debug)] +pub struct DecorrelateLateralJoin {} + +impl DecorrelateLateralJoin { + #[allow(missing_docs)] + pub fn new() -> Self { + Self::default() + } +} + +impl OptimizerRule for DecorrelateLateralJoin { + fn supports_rewrite(&self) -> bool { + true + } + + fn rewrite( + &self, + plan: LogicalPlan, + config: &dyn OptimizerConfig, + ) -> Result<Transformed<LogicalPlan>> { + // Find cross joins with outer column references on the right side (i.e., the apply operator). + let LogicalPlan::Join(join) = &plan else { + return Ok(Transformed::no(plan)); + }; + if join.join_type != JoinType::Inner { + return Ok(Transformed::no(plan)); + } + // TODO: this makes the rule to be quadratic to the number of nodes, in theory, we can build this property Review Comment: I believe you can cause `rewrite` to be called in a bottom up fashion by using: https://docs.rs/datafusion/latest/datafusion/optimizer/trait.OptimizerRule.html#method.apply_order Then you could maybe add a `contains_outer_reference` type flag to `DecorrelateLateralJoin` ########## datafusion/optimizer/src/decorrelate_lateral_join.rs: ########## @@ -0,0 +1,106 @@ +// 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. + +//! [`DecorrelateLateralJoin`] decorrelates logical plans produced by lateral joins. + +use crate::optimizer::ApplyOrder; +use crate::{decorrelate_predicate_subquery, OptimizerConfig, OptimizerRule}; + +use datafusion_common::tree_node::{Transformed, TreeNodeRecursion, TreeNodeVisitor}; +use datafusion_common::Result; +use datafusion_expr::logical_plan::JoinType; +use datafusion_expr::LogicalPlan; + +/// Optimizer rule for rewriting lateral joins to joins +#[derive(Default, Debug)] +pub struct DecorrelateLateralJoin {} + +impl DecorrelateLateralJoin { + #[allow(missing_docs)] + pub fn new() -> Self { + Self::default() + } +} + +impl OptimizerRule for DecorrelateLateralJoin { + fn supports_rewrite(&self) -> bool { + true + } + + fn rewrite( + &self, + plan: LogicalPlan, + config: &dyn OptimizerConfig, + ) -> Result<Transformed<LogicalPlan>> { + // Find cross joins with outer column references on the right side (i.e., the apply operator). + let LogicalPlan::Join(join) = &plan else { + return Ok(Transformed::no(plan)); + }; + if join.join_type != JoinType::Inner { + return Ok(Transformed::no(plan)); + } + // TODO: this makes the rule to be quadratic to the number of nodes, in theory, we can build this property + // bottom-up. + if !plan_contains_outer_reference(&join.right) { + return Ok(Transformed::no(plan)); + } + // The right side contains outer references, we need to decorrelate it. + let LogicalPlan::Subquery(subquery) = &*join.right else { + return Ok(Transformed::no(plan)); + }; + let alias = config.alias_generator(); + let Some(new_plan) = decorrelate_predicate_subquery::build_join( + &join.left, + subquery.subquery.as_ref(), + None, + join.join_type, + alias.next("__lateral_sq"), + )? + else { + return Ok(Transformed::no(plan)); + }; + Ok(Transformed::new(new_plan, true, TreeNodeRecursion::Jump)) + } + + fn name(&self) -> &str { + "decorrelate_lateral_join" + } + + fn apply_order(&self) -> Option<ApplyOrder> { + Some(ApplyOrder::TopDown) + } +} + +fn plan_contains_outer_reference(plan: &LogicalPlan) -> bool { + struct Visitor { + contains: bool, + } + impl<'n> TreeNodeVisitor<'n> for Visitor { + type Node = LogicalPlan; + fn f_down(&mut self, plan: &'n LogicalPlan) -> Result<TreeNodeRecursion> { + if plan.contains_outer_reference() { + self.contains = true; + Ok(TreeNodeRecursion::Stop) + } else { + Ok(TreeNodeRecursion::Continue) + } + } + } + let mut visitor = Visitor { contains: false }; + plan.visit_with_subqueries(&mut visitor).unwrap(); + visitor.contains Review Comment: I think you can do this more simply using `apply_subqueries` as described here: https://datafusion.apache.org/library-user-guide/query-optimizer.html#recursively-walk-an-expression-tree Something like (untested): ```rust fn plan_contains_outer_reference(plan: &LogicalPlan) -> bool { let mut contains = false; plan.apply_subqueries(|plan| { if plan.contains_outer_reference() { self.contains = true; Ok(TreeNodeRecursion::Stop) } else { Ok(TreeNodeRecursion::Continue) } }).unwrap(); contains } ``` ########## datafusion/sqllogictest/test_files/join.slt.part: ########## @@ -1312,3 +1312,85 @@ SELECT a+b*2, statement ok drop table t1; + + +statement ok +CREATE TABLE t1(v0 BIGINT, v1 BIGINT); + +statement ok +CREATE TABLE t0(v0 BIGINT, v1 BIGINT); + +statement ok Review Comment: Thanks! Could we please add some negative cases to these tests too such as: 1. When there are two subqueries 2. When the subqueries have no correlation ########## datafusion/sqllogictest/test_files/join.slt.part: ########## @@ -1312,3 +1312,85 @@ SELECT a+b*2, statement ok drop table t1; + + +statement ok +CREATE TABLE t1(v0 BIGINT, v1 BIGINT); + +statement ok +CREATE TABLE t0(v0 BIGINT, v1 BIGINT); + +statement ok +INSERT INTO t0(v0, v1) VALUES (1, 1), (1, 2), (3, 3); + +statement ok +INSERT INTO t1(v0, v1) VALUES (1, 1), (3, 2), (3, 5); + +query TT +explain SELECT * +FROM t0, +LATERAL (SELECT sum(v1) FROM t1 WHERE t0.v0 = t1.v0); +---- +logical_plan +01)Projection: t0.v0, t0.v1, sum(t1.v1) +02)--Inner Join: t0.v0 = __lateral_sq_1.v0 +03)----TableScan: t0 projection=[v0, v1] +04)----SubqueryAlias: __lateral_sq_1 +05)------Projection: sum(t1.v1), t1.v0 +06)--------Aggregate: groupBy=[[t1.v0]], aggr=[[sum(t1.v1)]] +07)----------TableScan: t1 projection=[v0, v1] +physical_plan +01)ProjectionExec: expr=[v0@1 as v0, v1@2 as v1, sum(t1.v1)@0 as sum(t1.v1)] Review Comment: So the DuckDB plan has 2 joins in it (I don't know what a `RIGHT_DELIM_JOIN` is) but this plan has only one ``` D explain SELECT * FROM t0, LATERAL (SELECT sum(v1) FROM t1 WHERE t0.v0 = t1.v0); ┌─────────────────────────────┐ │┌───────────────────────────┐│ ││ Physical Plan ││ │└───────────────────────────┘│ └─────────────────────────────┘ ┌───────────────────────────┐ │ PROJECTION │ │ ──────────────────── │ │ v0 │ │ v1 │ │ sum(v1) │ │ │ │ ~3 Rows │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ RIGHT_DELIM_JOIN │ │ ──────────────────── │ │ Join Type: INNER │ │ │ │ Conditions: ├──────────────┐ │ v0 IS NOT DISTINCT FROM v0│ │ │ │ │ │ ~3 Rows │ │ └─────────────┬─────────────┘ │ ┌─────────────┴─────────────┐┌─────────────┴─────────────┐ │ SEQ_SCAN ││ HASH_JOIN │ │ ──────────────────── ││ ──────────────────── │ │ t0 ││ Join Type: INNER │ │ ││ │ │ Projections: ││ Conditions: ├───────────────────────────────────────────┐ │ v0 ││ v0 IS NOT DISTINCT FROM v0│ │ │ v1 ││ │ │ │ ││ │ │ │ ~3 Rows ││ ~3 Rows │ │ └───────────────────────────┘└─────────────┬─────────────┘ │ ┌─────────────┴─────────────┐ ┌─────────────┴─────────────┐ │ PROJECTION │ │ DUMMY_SCAN │ │ ──────────────────── │ │ │ │ sum(v1) │ │ │ │ v0 │ │ │ │ │ │ │ │ ~1 Rows │ │ │ └─────────────┬─────────────┘ └───────────────────────────┘ ┌─────────────┴─────────────┐ │ HASH_JOIN │ │ ──────────────────── │ │ Join Type: LEFT │ │ │ │ Conditions: ├──────────────┐ │ v0 IS NOT DISTINCT FROM #0│ │ │ │ │ │ ~1 Rows │ │ └─────────────┬─────────────┘ │ ┌─────────────┴─────────────┐┌─────────────┴─────────────┐ │ DELIM_SCAN ││ PROJECTION │ │ ──────────────────── ││ ──────────────────── │ │ Delim Index: 1 ││__internal_decompress_integ│ │ ││ ral_bigint(#0, 1) │ │ ││ #1 │ │ ││ │ │ ~1 Rows ││ ~0 Rows │ └───────────────────────────┘└─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ PERFECT_HASH_GROUP_BY │ │ ──────────────────── │ │ Groups: #0 │ │ │ │ Aggregates: │ │ sum_no_overflow(#1) │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ PROJECTION │ │ ──────────────────── │ │ v0 │ │ v1 │ │ │ │ ~3 Rows │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ PROJECTION │ │ ──────────────────── │ │__internal_compress_integra│ │ l_utinyint(#0, 1) │ │ #1 │ │ │ │ ~3 Rows │ └─────────────┬─────────────┘ ┌─────────────┴─────────────┐ │ SEQ_SCAN │ │ ──────────────────── │ │ t1 │ │ │ │ Projections: │ │ v0 │ │ v1 │ │ │ │ ~3 Rows │ └───────────────────────────┘ ``` -- This is an automated message from the Apache Git Service. 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