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Posted to github@arrow.apache.org by "jackwener (via GitHub)" <gi...@apache.org> on 2023/04/26 05:58:43 UTC
[GitHub] [arrow-datafusion] jackwener commented on a diff in pull request #6084: Move Scalar Subquery validation logic to the Analyzer
jackwener commented on code in PR #6084:
URL: https://github.com/apache/arrow-datafusion/pull/6084#discussion_r1174520433
##########
datafusion/optimizer/src/analyzer/subquery.rs:
##########
@@ -0,0 +1,340 @@
+// 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 crate::analyzer::check_plan;
+use crate::utils::{collect_subquery_cols, split_conjunction};
+use datafusion_common::tree_node::{TreeNode, VisitRecursion};
+use datafusion_common::{DataFusionError, Result};
+use datafusion_expr::expr_rewriter::strip_outer_reference;
+use datafusion_expr::{
+ Aggregate, BinaryExpr, Cast, Expr, Filter, Join, JoinType, LogicalPlan, Operator,
+ Window,
+};
+use std::ops::Deref;
+
+/// Do necessary check on subquery expressions and fail the invalid plan
+/// 1) Check whether the outer plan is in the allowed outer plans list to use subquery expressions,
+/// the allowed while list: [Projection, Filter, Window, Aggregate, Join].
+/// 2) Check whether the inner plan is in the allowed inner plans list to use correlated(outer) expressions.
+/// 3) Check and validate unsupported cases to use the correlated(outer) expressions inside the subquery(inner) plans/inner expressions.
+/// For example, we do not want to support to use correlated expressions as the Join conditions in the subquery plan when the Join
+/// is a Full Out Join
+pub fn check_subquery_expr(
+ outer_plan: &LogicalPlan,
+ inner_plan: &LogicalPlan,
+ expr: &Expr,
+) -> Result<()> {
+ check_plan(inner_plan)?;
+ if let Expr::ScalarSubquery(subquery) = expr {
+ // Scalar subquery should only return one column
+ if subquery.subquery.schema().fields().len() > 1 {
+ return Err(datafusion_common::DataFusionError::Plan(
+ "Scalar subquery should only return one column".to_string(),
+ ));
+ }
+ // Correlated scalar subquery must be aggregated to return at most one row
+ if !subquery.outer_ref_columns.is_empty() {
+ match strip_inner_query(inner_plan) {
+ LogicalPlan::Aggregate(agg) => {
+ check_aggregation_in_scalar_subquery(inner_plan, agg)
+ }
+ LogicalPlan::Filter(Filter { input, .. })
+ if matches!(input.as_ref(), LogicalPlan::Aggregate(_)) =>
+ {
+ if let LogicalPlan::Aggregate(agg) = input.as_ref() {
+ check_aggregation_in_scalar_subquery(inner_plan, agg)
+ } else {
+ Ok(())
+ }
+ }
+ _ => {
+ if inner_plan
+ .max_rows()
+ .filter(|max_row| *max_row <= 1)
+ .is_some()
+ {
+ Ok(())
+ } else {
+ Err(DataFusionError::Plan(
+ "Correlated scalar subquery must be aggregated to return at most one row"
+ .to_string(),
+ ))
+ }
+ }
+ }?;
+ match outer_plan {
+ LogicalPlan::Projection(_)
+ | LogicalPlan::Filter(_) => Ok(()),
+ LogicalPlan::Aggregate(Aggregate {group_expr, aggr_expr,..}) => {
+ if group_expr.contains(expr) && !aggr_expr.contains(expr) {
+ // TODO revisit this validation logic
+ Err(DataFusionError::Plan(
+ "Correlated scalar subquery in the GROUP BY clause must also be in the aggregate expressions"
+ .to_string(),
+ ))
+ } else {
+ Ok(())
+ }
+ },
+ _ => Err(DataFusionError::Plan(
+ "Correlated scalar subquery can only be used in Projection, Filter, Aggregate plan nodes"
+ .to_string(),
+ ))
+ }?;
+ }
+ check_correlations_in_subquery(inner_plan, true)
+ } else {
+ match outer_plan {
+ LogicalPlan::Projection(_)
+ | LogicalPlan::Filter(_)
+ | LogicalPlan::Window(_)
+ | LogicalPlan::Aggregate(_)
+ | LogicalPlan::Join(_) => Ok(()),
+ _ => Err(DataFusionError::Plan(
+ "In/Exist subquery can only be used in \
+ Projection, Filter, Window functions, Aggregate and Join plan nodes"
+ .to_string(),
+ )),
+ }?;
+ check_correlations_in_subquery(inner_plan, false)
+ }
+}
+
+// Recursively check the unsupported outer references in the sub query plan.
+fn check_correlations_in_subquery(
+ inner_plan: &LogicalPlan,
+ is_scalar: bool,
+) -> Result<()> {
+ check_inner_plan(inner_plan, is_scalar, false, true)
+}
+
+// Recursively check the unsupported outer references in the sub query plan.
+fn check_inner_plan(
+ inner_plan: &LogicalPlan,
+ is_scalar: bool,
+ is_aggregate: bool,
+ can_contain_outer_ref: bool,
+) -> Result<()> {
+ if !can_contain_outer_ref && contains_outer_reference(inner_plan) {
+ return Err(DataFusionError::Plan(
+ "Accessing outer reference columns is not allowed in the plan".to_string(),
+ ));
+ }
+ // We want to support as many operators as possible inside the correlated subquery
+ match inner_plan {
+ LogicalPlan::Aggregate(_) => {
+ inner_plan.apply_children(&mut |plan| {
+ check_inner_plan(plan, is_scalar, true, can_contain_outer_ref)?;
+ Ok(VisitRecursion::Continue)
+ })?;
+ Ok(())
+ }
+ LogicalPlan::Filter(Filter {
+ predicate, input, ..
+ }) => {
+ let (correlated, _): (Vec<_>, Vec<_>) = split_conjunction(predicate)
+ .into_iter()
+ .partition(|e| e.contains_outer());
+ let maybe_unsupport = correlated
+ .into_iter()
+ .filter(|expr| !can_pullup_over_aggregation(expr))
+ .collect::<Vec<_>>();
+ if is_aggregate && is_scalar && !maybe_unsupport.is_empty() {
+ return Err(DataFusionError::Plan(format!(
+ "Correlated column is not allowed in predicate: {:?}",
+ predicate
+ )));
+ }
+ check_inner_plan(input, is_scalar, is_aggregate, can_contain_outer_ref)
+ }
+ LogicalPlan::Window(window) => {
+ check_mixed_out_refer_in_window(window)?;
+ inner_plan.apply_children(&mut |plan| {
+ check_inner_plan(plan, is_scalar, is_aggregate, can_contain_outer_ref)?;
+ Ok(VisitRecursion::Continue)
+ })?;
+ Ok(())
+ }
+ LogicalPlan::Projection(_)
+ | LogicalPlan::Distinct(_)
+ | LogicalPlan::Sort(_)
+ | LogicalPlan::CrossJoin(_)
+ | LogicalPlan::Union(_)
+ | LogicalPlan::TableScan(_)
+ | LogicalPlan::EmptyRelation(_)
+ | LogicalPlan::Limit(_)
+ | LogicalPlan::Values(_)
+ | LogicalPlan::Subquery(_)
+ | LogicalPlan::SubqueryAlias(_) => {
+ inner_plan.apply_children(&mut |plan| {
+ check_inner_plan(plan, is_scalar, is_aggregate, can_contain_outer_ref)?;
+ Ok(VisitRecursion::Continue)
+ })?;
+ Ok(())
+ }
+ LogicalPlan::Join(Join {
+ left,
+ right,
+ join_type,
+ ..
+ }) => match join_type {
+ JoinType::Inner => {
+ inner_plan.apply_children(&mut |plan| {
+ check_inner_plan(
+ plan,
+ is_scalar,
+ is_aggregate,
+ can_contain_outer_ref,
+ )?;
+ Ok(VisitRecursion::Continue)
+ })?;
+ Ok(())
+ }
+ JoinType::Left | JoinType::LeftSemi | JoinType::LeftAnti => {
+ check_inner_plan(left, is_scalar, is_aggregate, can_contain_outer_ref)?;
+ check_inner_plan(right, is_scalar, is_aggregate, false)
+ }
+ JoinType::Right | JoinType::RightSemi | JoinType::RightAnti => {
+ check_inner_plan(left, is_scalar, is_aggregate, false)?;
+ check_inner_plan(right, is_scalar, is_aggregate, can_contain_outer_ref)
+ }
+ JoinType::Full => {
+ inner_plan.apply_children(&mut |plan| {
+ check_inner_plan(plan, is_scalar, is_aggregate, false)?;
+ Ok(VisitRecursion::Continue)
+ })?;
+ Ok(())
+ }
+ },
+ _ => Err(DataFusionError::Plan(
+ "Unsupported operator in the subquery plan.".to_string(),
+ )),
+ }
+}
+
+fn contains_outer_reference(inner_plan: &LogicalPlan) -> bool {
+ inner_plan
+ .expressions()
+ .iter()
+ .any(|expr| expr.contains_outer())
+}
+
+fn check_aggregation_in_scalar_subquery(
+ inner_plan: &LogicalPlan,
+ agg: &Aggregate,
+) -> Result<()> {
+ if agg.aggr_expr.is_empty() {
+ return Err(DataFusionError::Plan(
+ "Correlated scalar subquery must be aggregated to return at most one row"
+ .to_string(),
+ ));
+ }
+ if !agg.group_expr.is_empty() {
+ let correlated_exprs = get_correlated_expressions(inner_plan)?;
+ let inner_subquery_cols =
+ collect_subquery_cols(&correlated_exprs, agg.input.schema().clone())?;
+ let mut group_columns = agg
+ .group_expr
+ .iter()
+ .map(|group| Ok(group.to_columns()?.into_iter().collect::<Vec<_>>()))
+ .collect::<Result<Vec<_>>>()?
+ .into_iter()
+ .flatten();
+
+ if !group_columns.all(|group| inner_subquery_cols.contains(&group)) {
+ // Group BY columns must be a subset of columns in the correlated expressions
+ return Err(DataFusionError::Plan(
+ "A GROUP BY clause in a scalar correlated subquery cannot contain non-correlated columns"
+ .to_string(),
+ ));
+ }
+ }
+ Ok(())
+}
+
+fn strip_inner_query(inner_plan: &LogicalPlan) -> &LogicalPlan {
+ match inner_plan {
+ LogicalPlan::Projection(projection) => {
+ strip_inner_query(projection.input.as_ref())
+ }
+ LogicalPlan::SubqueryAlias(alias) => strip_inner_query(alias.input.as_ref()),
+ other => other,
+ }
+}
+
+fn get_correlated_expressions(inner_plan: &LogicalPlan) -> Result<Vec<Expr>> {
+ let mut exprs = vec![];
+ inner_plan.apply(&mut |plan| {
+ if let LogicalPlan::Filter(Filter { predicate, .. }) = plan {
+ let (correlated, _): (Vec<_>, Vec<_>) = split_conjunction(predicate)
+ .into_iter()
+ .partition(|e| e.contains_outer());
+
+ correlated
+ .into_iter()
+ .for_each(|expr| exprs.push(strip_outer_reference(expr.clone())));
+ return Ok(VisitRecursion::Continue);
+ }
+ Ok(VisitRecursion::Continue)
+ })?;
+ Ok(exprs)
+}
+
+/// Check whether the expression can pull up over the aggregation without change the result of the query
+fn can_pullup_over_aggregation(expr: &Expr) -> bool {
+ if let Expr::BinaryExpr(BinaryExpr {
+ left,
+ op: Operator::Eq,
+ right,
+ }) = expr
+ {
+ match (left.deref(), right.deref()) {
+ (Expr::Column(_), right) if right.to_columns().unwrap().is_empty() => true,
+ (left, Expr::Column(_)) if left.to_columns().unwrap().is_empty() => true,
+ (Expr::Cast(Cast { expr, .. }), right)
+ if matches!(expr.deref(), Expr::Column(_))
+ && right.to_columns().unwrap().is_empty() =>
+ {
+ true
+ }
+ (left, Expr::Cast(Cast { expr, .. }))
+ if matches!(expr.deref(), Expr::Column(_))
+ && left.to_columns().unwrap().is_empty() =>
+ {
+ true
+ }
+ (_, _) => false,
+ }
+ } else {
+ false
+ }
+}
+
+/// Check whether the window expressions contain a mixture of out reference columns and inner columns
+fn check_mixed_out_refer_in_window(window: &Window) -> Result<()> {
+ let mixed = window.window_expr.iter().any(|win_expr| {
+ win_expr.contains_outer() && !win_expr.to_columns().unwrap().is_empty()
Review Comment:
```suggestion
win_expr.contains_outer() && !win_expr.to_columns()?.is_empty()
```
##########
datafusion/core/tests/sql/subqueries.rs:
##########
@@ -203,7 +203,202 @@ async fn subquery_not_allowed() -> Result<()> {
let err = dataframe.into_optimized_plan().err().unwrap();
assert_eq!(
- r#"Context("check_analyzed_plan", Plan("In/Exist subquery can not be used in Sort plan nodes"))"#,
+ r#"Context("check_analyzed_plan", Plan("In/Exist subquery can only be used in Projection, Filter, Window functions, Aggregate and Join plan nodes"))"#,
Review Comment:
👍
##########
datafusion/expr/src/logical_plan/plan.rs:
##########
@@ -484,6 +484,97 @@ impl LogicalPlan {
_ => Ok(self),
}
}
+
+ /// Returns the maximum number of rows that this plan can output.
+ pub fn max_rows(self: &LogicalPlan) -> Option<usize> {
+ match self {
+ LogicalPlan::Projection(Projection { input, .. }) => input.max_rows(),
+ LogicalPlan::Filter(Filter { input, .. }) => input.max_rows(),
+ LogicalPlan::Window(Window { input, .. }) => input.max_rows(),
+ LogicalPlan::Aggregate(Aggregate {
+ input, group_expr, ..
+ }) => {
+ if group_expr.is_empty() {
+ Some(1)
+ } else {
+ input.max_rows()
+ }
+ }
+ LogicalPlan::Sort(Sort { input, fetch, .. }) => {
+ match (fetch, input.max_rows()) {
+ (Some(fetch_limit), Some(input_max)) => {
+ Some(input_max.min(*fetch_limit))
+ }
+ (Some(fetch_limit), None) => Some(*fetch_limit),
+ (None, Some(input_max)) => Some(input_max),
+ (None, None) => None,
+ }
+ }
+ LogicalPlan::Join(Join {
+ left,
+ right,
+ join_type,
+ ..
+ }) => match join_type {
+ JoinType::Inner | JoinType::Left | JoinType::Right | JoinType::Full => {
+ match (left.max_rows(), right.max_rows()) {
+ (Some(left_max), Some(right_max)) => {
+ let min_rows = match join_type {
+ JoinType::Left => left_max,
+ JoinType::Right => right_max,
+ JoinType::Full => left_max + right_max,
+ _ => 0,
+ };
+ Some((left_max * right_max).max(min_rows))
+ }
+ _ => None,
+ }
+ }
+ JoinType::LeftSemi | JoinType::LeftAnti => left.max_rows(),
+ JoinType::RightSemi | JoinType::RightAnti => right.max_rows(),
+ },
+ LogicalPlan::CrossJoin(CrossJoin { left, right, .. }) => {
+ match (left.max_rows(), right.max_rows()) {
+ (Some(left_max), Some(right_max)) => Some(left_max * right_max),
+ _ => None,
+ }
+ }
+ LogicalPlan::Repartition(Repartition { input, .. }) => input.max_rows(),
+ LogicalPlan::Union(Union { inputs, .. }) => inputs
+ .iter()
+ .map(|plan| plan.max_rows())
+ .try_fold(0usize, |mut acc, input_max| {
+ if let Some(i_max) = input_max {
+ acc += i_max;
+ Some(acc)
+ } else {
+ None
+ }
+ }),
+ LogicalPlan::TableScan(TableScan { fetch, .. }) => *fetch,
Review Comment:
I'm not sure about whether `fetch` is accurate.
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