Multiple optimizer passes #3880
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -40,6 +40,7 @@ use datafusion_common::{DataFusionError, Result}; | |
| use datafusion_expr::logical_plan::LogicalPlan; | ||
| use log::{debug, trace, warn}; | ||
| use std::sync::Arc; | ||
| use std::time::Instant; | ||
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| /// `OptimizerRule` transforms one ['LogicalPlan'] into another which | ||
| /// computes the same results, but in a potentially more efficient | ||
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@@ -71,6 +72,8 @@ pub struct OptimizerConfig { | |
| skip_failing_rules: bool, | ||
| /// Specify whether to enable the filter_null_keys rule | ||
| filter_null_keys: bool, | ||
| /// Maximum number of times to run optimizer against a plan | ||
| max_passes: u8, | ||
| } | ||
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| impl OptimizerConfig { | ||
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@@ -81,6 +84,7 @@ impl OptimizerConfig { | |
| next_id: 0, // useful for generating things like unique subquery aliases | ||
| skip_failing_rules: true, | ||
| filter_null_keys: true, | ||
| max_passes: 3, | ||
| } | ||
| } | ||
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@@ -107,6 +111,12 @@ impl OptimizerConfig { | |
| self | ||
| } | ||
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| /// Specify how many times to attempt to optimize the plan | ||
| pub fn with_max_passes(mut self, v: u8) -> Self { | ||
| self.max_passes = v; | ||
| self | ||
| } | ||
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| /// Generate the next ID needed | ||
| pub fn next_id(&mut self) -> usize { | ||
| self.next_id += 1; | ||
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@@ -189,38 +199,57 @@ impl Optimizer { | |
| where | ||
| F: FnMut(&LogicalPlan, &dyn OptimizerRule), | ||
| { | ||
| let start_time = Instant::now(); | ||
| let mut plan_str = format!("{}", plan.display_indent()); | ||
| let mut new_plan = plan.clone(); | ||
| let mut i = 0; | ||
| while i < optimizer_config.max_passes { | ||
| log_plan(&format!("Optimizer input (pass {})", i), &new_plan); | ||
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| for rule in &self.rules { | ||
| let result = rule.optimize(&new_plan, optimizer_config); | ||
| match result { | ||
| Ok(plan) => { | ||
| new_plan = plan; | ||
| observer(&new_plan, rule.as_ref()); | ||
| log_plan(rule.name(), &new_plan); | ||
| } | ||
| Err(ref e) => { | ||
| if optimizer_config.skip_failing_rules { | ||
| // Note to future readers: if you see this warning it signals a | ||
| // bug in the DataFusion optimizer. Please consider filing a ticket | ||
| // https://github.com/apache/arrow-datafusion | ||
| warn!( | ||
| "Skipping optimizer rule '{}' due to unexpected error: {}", | ||
| rule.name(), | ||
| e | ||
| ); | ||
| } else { | ||
| return Err(DataFusionError::Internal(format!( | ||
| "Optimizer rule '{}' failed due to unexpected error: {}", | ||
| rule.name(), | ||
| e | ||
| ))); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| log_plan(&format!("Optimized plan (pass {})", i), &new_plan); | ||
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| // TODO this is an expensive way to see if the optimizer did anything and | ||
| // it would be better to change the OptimizerRule trait to return an Option | ||
| // instead | ||
| let new_plan_str = format!("{}", new_plan.display_indent()); | ||
| if plan_str == new_plan_str { | ||
| // plan did not change, so no need to continue trying to optimize | ||
| debug!("optimizer pass {} did not make changes", i); | ||
| break; | ||
| } | ||
|
Comment on lines
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There was a problem hiding this comment. +1! This is probably a follow-up item; but instead of having the optimizer decide on this (by returning an option), it might also make sense to compute a unique plan id (bottom up) so that we can also use this to detect optimization cycles. A very basic example is (assuming each letter is a unique plan id) There was a problem hiding this comment. That's a great idea. Thanks @isidentical. I will write up an issue. There was a problem hiding this comment. I filed #3892 to track this |
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| plan_str = new_plan_str; | ||
| i += 1; | ||
| } | ||
| log_plan("Final optimized plan", &new_plan); | ||
| debug!("Optimizer took {} ms", start_time.elapsed().as_millis()); | ||
| Ok(new_plan) | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -135,7 +135,7 @@ fn optimize_plan( | |
| _optimizer_config: &OptimizerConfig, | ||
| ) -> Result<LogicalPlan> { | ||
| let mut new_required_columns = required_columns.clone(); | ||
| let new_plan = match plan { | ||
| LogicalPlan::Projection(Projection { | ||
| input, | ||
| expr, | ||
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@@ -509,7 +509,25 @@ fn optimize_plan( | |
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| from_plan(plan, &expr, &new_inputs) | ||
| } | ||
| }; | ||
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| // when this rule is applied multiple times it will insert duplicate nested projections, | ||
| // so we catch this here | ||
| let with_dupe_projection_removed = match new_plan? { | ||
| LogicalPlan::Projection(p) => match p.input.as_ref() { | ||
| LogicalPlan::Projection(p2) if projection_equal(&p, p2) => { | ||
| LogicalPlan::Projection(p2.clone()) | ||
| } | ||
| _ => LogicalPlan::Projection(p), | ||
| }, | ||
| other => other, | ||
| }; | ||
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There was a problem hiding this comment. This is the fix for #3881 |
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| Ok(with_dupe_projection_removed) | ||
| } | ||
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| fn projection_equal(p: &Projection, p2: &Projection) -> bool { | ||
| p.expr.len() == p2.expr.len() && p.expr.iter().zip(&p2.expr).all(|(l, r)| l == r) | ||
| } | ||
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| #[cfg(test)] | ||
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The order changed here