perf(optimizer): generic in-place mutable rewrite to obsolete per-rule fast-paths - #22728
Draft
zhuqi-lucas wants to merge 4 commits into
Draft
perf(optimizer): generic in-place mutable rewrite to obsolete per-rule fast-paths#22728zhuqi-lucas wants to merge 4 commits into
zhuqi-lucas wants to merge 4 commits into
Conversation
Generalizes the in-place `Arc::make_mut` traversal adriangb landed in apache#22298 so all logical-optimizer rules — not just the no-subqueries fast-path — get the cheaper recursion. Closes apache#22616. Two pieces: 1. `map_children_and_subqueries_mut` — extends `map_children_mut` with a subquery-plan descent. Direct children stay on the in-place path; subqueries borrow the plan briefly via `mem::take` to reach the ownership-based `LogicalPlan::map_subqueries`, whose per-node `has_subquery_expressions` fast-path keeps subquery-free nodes allocation-free. With this in place, `rewrite_plan_in_place` no longer needs the `plan_has_subqueries` gate the driver was using — plans with subqueries can now share the in-place recursion. Removes `plan_has_subqueries`, the `TreeNodeRewriter`-based `Rewriter` shim, and the `has_subqueries ? owned : in_place` branch in `Optimizer::optimize_internal`. 2. `rewrite_children_in_place` — in-place equivalent of the `map_uncorrelated_subqueries` + `map_children` pattern that rules with `apply_order = None` use to drive their own recursion. `EliminateCrossJoin` and `CommonSubexprEliminate` are the two such rules in-tree; both convert. The net effect: when a rule returns `Transformed::no` for a child, the parent `LogicalPlan` variant is no longer destructured-and-rebuilt at every recursive layer — the child's `Arc` is reused via `Arc::make_mut`. Profile-guided: sql_planner profiling on `logical_plan_tpch_all` / `optimizer_tpch_all` showed ~17% of active CPU in `Vec/Box/Arc TreeNodeContainer` walking; this path is what generates that load. Net diff: -28 lines (the `Rewriter` shim + `plan_has_subqueries` together outweigh the two new helpers). 711 optimizer unit tests still pass. SLT broad sweep — subquery / cse / joins / predicates / aggregate / tpch (16 files) — all pass. `cargo clippy -p datafusion-optimizer --all-targets -- -D warnings` clean.
The new `map_children_and_subqueries_mut` / `rewrite_children_in_place` helpers were only covered through the existing 711 optimizer tests + SLT sweep — fine for behaviour but not great for pinning each helper's contract on its own. Five targeted tests: - `map_children_and_subqueries_mut_no_children` — no children + no subqueries returns `Ok(false)` and never invokes `f`. - `map_children_and_subqueries_mut_walks_direct_children` — `Filter`'s `TableScan` input is visited exactly once. - `map_children_and_subqueries_mut_descends_into_subquery` — pins the subquery descent that `map_children_mut` alone is missing: `Filter(IN (SELECT ...))` visits the outer `TableScan` *and* the subquery plan inside the predicate. - `map_children_and_subqueries_mut_reports_changes` — closure returning `true` propagates as `changed == true`. - `rewrite_children_in_place_drives_rule_recursion` — bridges `&mut LogicalPlan` callback to ownership-based `OptimizerRule::rewrite` API and visits each child exactly once with a recording rule.
zhuqi-lucas
force-pushed
the
perf/in-place-mutable-rewrite
branch
from
June 3, 2026 06:18
3ae2c6d to
cc54f98
Compare
Contributor
Author
|
run benchmark sql_planner |
|
🤖 Criterion benchmark running (GKE) | trigger CPU Details (lscpu)Comparing perf/in-place-mutable-rewrite (cc54f98) to 7bf54db (merge-base) diff File an issue against this benchmark runner |
|
🤖 Criterion benchmark completed (GKE) | trigger Instance: CPU Details (lscpu)Details
Resource Usagebase (merge-base)
branch
File an issue against this benchmark runner |
…sion Per-node has_subquery_expressions walks were dominating optimizer cost on subquery-free plans (the common case for join-heavy workloads). Bench showed optimizer_join_chain_4 +12%, optimizer_tpch_all +3%, even though logical_plan_tpch_all (full pipeline) was -5%. Restore the one-shot whole-plan plan_has_subqueries check at the driver, propagate has_subqueries: bool through rewrite_plan_in_place, and dispatch to map_children_mut (no subquery descent) when false. For the ApplyOrder::None path, also add a per-node fast-path inside map_children_and_subqueries_mut to skip the mem::take + map_subqueries roundtrip when the node carries no subquery expressions. Make LogicalPlan::has_subquery_expressions pub so the optimizer can reuse it without duplicating the walk. Also fixes the cargo doc -D warnings CI break (unresolved intra-doc link to TreeNode::rewrite).
Contributor
Author
|
run benchmark sql_planner |
|
🤖 Criterion benchmark running (GKE) | trigger CPU Details (lscpu)Comparing perf/in-place-mutable-rewrite (02748ae) to e71bd56 (merge-base) diff File an issue against this benchmark runner |
|
🤖 Criterion benchmark completed (GKE) | trigger Instance: CPU Details (lscpu)Details
Resource Usagebase (merge-base)
branch
File an issue against this benchmark runner |
|
Thank you for your contribution. Unfortunately, this pull request is stale because it has been open 60 days with no activity. Please remove the stale label or comment or this will be closed in 7 days. |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Which issue does this PR close?
Closes #22616.
Rationale for this change
#22298 added an in-place
Arc::make_muttraversal for the optimizer driver, but only used it when the plan had no subqueries — plans with subqueries fell back to the ownership-based path that destructures and rebuilds eachLogicalPlanvariant at every recursive layer. TwoApplyOrder::Nonerules (EliminateCrossJoin,CommonSubexprEliminate) also never got the in-place treatment.Profiling
sql_planner(pre-#22298) showed a non-trivial share of CPU in those ownership-based tree walks. Most of that has already been collected by #22298 — this PR closes the remaining two gaps.Scope
This PR converts:
rewrite_plan_in_place) — subquery-bearing plans now go through the in-place path too, no more fallback to owned recursion.EliminateCrossJoinandCommonSubexprEliminate— the twoApplyOrder::Nonerules with the simplemap_uncorrelated_subqueries+map_childrenpattern.Not converted (left for future work — each has its own non-uniform recursion shape that doesn't fit the generic helper):
OptimizeProjections— required-columns context plumbed top-down.RewriteSetComparison— restructures expressions, introduces aliases.UnionsToFilter— shape-dependent rewrites on Union nodes.Where the gain actually comes from
Of the two
ApplyOrder::Nonerules converted:CommonSubexprEliminateis where most of the value lands. It has no plan-level fast-path: every plan walks from root to leaf throughrewrite_children, including on plans where the rule's own targeted optimization has nothing to do at any node (Join,Repartition,Union,TableScan,Limit, ...). The in-place conversion saves the per-layer destructure/rebuild on every such walk.EliminateCrossJoinis marginal in practice: theplan_has_joinsfast-path landed in perf(optimizer): EliminateCrossJoin fast-path for join-free plans #22612 short-circuits the rule entirely on join-free plans, and on plans with joins the rule's main flattening logic usesArc::unwrap_or_clonedirectly rather thanrewrite_children.rewrite_childrenonly fires on the wrapping non-join layers (e.g. an outerProjectionabove a join chain) — small but non-zero.The third source of gain is the TopDown/BottomUp path: previously, any plan with even one subquery expression fell back to owned recursion for all ~17 rules in the pipeline. Now those plans stay on the in-place path.
What changes are included in this PR?
Two in-place helpers so all converted rules share the
Arc::make_mutpath:map_children_and_subqueries_mut— extendsmap_children_mutto also descend into subquery plans referenced from expressions (Expr::ScalarSubquery,InSubquery,Exists,SetComparison).rewrite_children_in_place— in-place equivalent of themap_uncorrelated_subqueries+map_childrenpattern.EliminateCrossJoinandCommonSubexprEliminateconvert to it.When a rule returns
Transformed::no, the parentLogicalPlanvariant is no longer destructured-and-rebuilt at every recursive layer.Subquery descent is gated by a one-shot whole-plan
plan_has_subqueriescheck per rule application: subquery-free plans (the common case for join-heavy workloads) fall through to plainmap_children_mutand pay zero subquery overhead — same shape as the #22298 fast path. Plans with subqueries get the new unified in-place recursion. TheApplyOrder::Nonepath additionally has a per-node fast-path insidemap_children_and_subqueries_mutto skip themem::take+map_subqueriesroundtrip when a node carries no subquery expressions.Are these changes tested?
subquery/cse/joins/predicates/aggregate/tpch(16 files) — all pass.Are there any user-facing changes?
No. Pure perf, no new APIs / config knobs.
LogicalPlan::has_subquery_expressionsis nowpubso the optimizer can call it without duplicating the walker.