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docs: Document that adding new optimizer rules are expensive #20348

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docs: Document that adding new optimizer rules are expensive
alamb Feb 13, 2026
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docs: Document that adding new optimizer rules are expensive
alamb Feb 13, 2026
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6 changes: 6 additions & 0 deletions datafusion/optimizer/src/optimizer.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -236,6 +236,12 @@ impl Default for Optimizer {
impl Optimizer {
/// Create a new optimizer using the recommended list of rules
pub fn new() -> Self {
// NOTEs:
// - The order of rules in this list is important, as it determines the
// order in which they are applied.
// - Adding a new rule here is expensive as it will be applied to all
// queries, and will likely increase the optimization time. Please extend
// existing rules when possible, rather than adding a new rule.
Comment on lines +242 to +244
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@adriangb adriangb Feb 16, 2026

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// - Adding a new rule here is expensive as it will be applied to all
// queries, and will likely increase the optimization time. Please extend
// existing rules when possible, rather than adding a new rule.
// - Adding a new rule here is expensive as it will be applied to all
// queries, and will likely increase the optimization time. Please extend
// existing rules when possible, rather than adding a new rule.
// If you do add a new rule considering having aggressive no-op paths
// (e.g. if the plan doesn't contain any of the nodes you are looking for
// return `Transformed::no`; only works if you control the traversal).

let rules: Vec<Arc<dyn OptimizerRule + Sync + Send>> = vec![
Arc::new(RewriteSetComparison::new()),
Arc::new(OptimizeUnions::new()),
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6 changes: 6 additions & 0 deletions datafusion/physical-optimizer/src/optimizer.rs
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Expand Up @@ -82,6 +82,12 @@ impl Default for PhysicalOptimizer {
impl PhysicalOptimizer {
/// Create a new optimizer using the recommended list of rules
pub fn new() -> Self {
// NOTEs:
// - The order of rules in this list is important, as it determines the
// order in which they are applied.
// - Adding a new rule here is expensive as it will be applied to all
// queries, and will likely increase the optimization time. Please extend
// existing rules when possible, rather than adding a new rule.
let rules: Vec<Arc<dyn PhysicalOptimizerRule + Send + Sync>> = vec![
// If there is a output requirement of the query, make sure that
// this information is not lost across different rules during optimization.
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