alamb commented on a change in pull request #288:
URL: https://github.com/apache/arrow-datafusion/pull/288#discussion_r629262731
##########
File path: datafusion/src/execution/context.rs
##########
@@ -740,6 +748,12 @@ impl ExecutionConfig {
}
}
+/// Current execution props
Review comment:
```suggestion
/// Holds per-execution properties and data (such as starting timestamps,
etc).
/// An instance of this struct is created each time a [`LogicalPlan`] is
prepared for
/// execution (optimized). If the same plan is optimized multiple times, a
new
/// `ExecutionProps` is created each time.
```
##########
File path: datafusion/src/optimizer/timestamp_evaluation.rs
##########
@@ -0,0 +1,177 @@
+// 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.
+
+//! Optimizer rule to replace timestamp expressions to constants.
+//! This saves time in planning and executing the query.
+use crate::error::Result;
+use crate::logical_plan::{Expr, LogicalPlan};
+use crate::optimizer::optimizer::OptimizerRule;
+
+use super::utils;
+use crate::execution::context::ExecutionProps;
+use crate::physical_plan::functions::BuiltinScalarFunction;
+use crate::scalar::ScalarValue;
+use chrono::{DateTime, Utc};
+
+/// Optimization rule that replaces timestamp expressions with their values
evaluated
Review comment:
What would you think about extending the `constant_folding` optimizer
rule instead of adding an entirely new rule?
I think you could probably add a case to the expression rewriter in
https://github.com/apache/arrow-datafusion/blob/master/datafusion/src/optimizer/constant_folding.rs#L122
for `Expr::ScalarFunction { fun: BuiltinScalarFunction::Now}}` and avoid the
need for all the code in this pass for traversing the expression tree.
##########
File path: datafusion/tests/sql.rs
##########
@@ -2738,6 +2738,24 @@ async fn test_cast_expressions() -> Result<()> {
Ok(())
}
+#[tokio::test]
+async fn test_timestamp_expressions() -> Result<()> {
+ let t1 = chrono::Utc::now().timestamp();
+ let mut ctx = ExecutionContext::new();
+ let actual = execute(&mut ctx, "SELECT NOW(), NOW() as t2").await;
+ let res1 = actual[0][0].as_str();
+ let res2 = actual[0][1].as_str();
+ let t3 = chrono::Utc::now().timestamp();
+ let t2_naive =
Review comment:
👍 good test.
##########
File path: datafusion/src/optimizer/timestamp_evaluation.rs
##########
@@ -0,0 +1,177 @@
+// 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.
+
+//! Optimizer rule to replace timestamp expressions to constants.
+//! This saves time in planning and executing the query.
+use crate::error::Result;
+use crate::logical_plan::{Expr, LogicalPlan};
+use crate::optimizer::optimizer::OptimizerRule;
+
+use super::utils;
+use crate::execution::context::ExecutionProps;
+use crate::physical_plan::functions::BuiltinScalarFunction;
+use crate::scalar::ScalarValue;
+use chrono::{DateTime, Utc};
+
+/// Optimization rule that replaces timestamp expressions with their values
evaluated
+pub struct TimestampEvaluation {}
+
+impl TimestampEvaluation {
+ #[allow(missing_docs)]
+ pub fn new() -> Self {
+ Self {}
+ }
+
+ /// Recursive function to optimize the now expression
+ pub fn rewrite_expr(&self, exp: &Expr, date_time: &DateTime<Utc>) ->
Result<Expr> {
+ let expressions = utils::expr_sub_expressions(exp).unwrap();
+ let expressions = expressions
+ .iter()
+ .map(|e| self.rewrite_expr(e, date_time))
+ .collect::<Result<Vec<_>>>()?;
+
+ let exp = match exp {
+ Expr::ScalarFunction {
+ fun: BuiltinScalarFunction::Now,
+ ..
+ } => Expr::Literal(ScalarValue::TimestampNanosecond(Some(
+ date_time.timestamp_nanos(),
+ ))),
+ _ => exp.clone(),
+ };
+ utils::rewrite_expression(&exp, &expressions)
+ }
+
+ fn optimize_with_datetime(
+ &self,
+ plan: &LogicalPlan,
+ date_time: &DateTime<Utc>,
+ ) -> Result<LogicalPlan> {
+ match plan {
+ LogicalPlan::Projection { .. } => {
+ let exprs = plan
+ .expressions()
+ .iter()
+ .map(|exp| self.rewrite_expr(exp, date_time).unwrap())
+ .collect::<Vec<_>>();
+
+ // apply the optimization to all inputs of the plan
+ let inputs = plan.inputs();
+ let new_inputs = inputs
+ .iter()
+ .map(|plan| self.optimize_with_datetime(*plan, date_time))
+ .collect::<Result<Vec<_>>>()?;
+
+ utils::from_plan(plan, &exprs, &new_inputs)
+ }
+ _ => {
+ let expr = plan.expressions();
+
+ // apply the optimization to all inputs of the plan
+ let inputs = plan.inputs();
+ let new_inputs = inputs
+ .iter()
+ .map(|plan| self.optimize_with_datetime(*plan, date_time))
+ .collect::<Result<Vec<_>>>()?;
+
+ utils::from_plan(plan, &expr, &new_inputs)
+ }
+ }
+ }
+}
+
+impl OptimizerRule for TimestampEvaluation {
+ fn optimize(
+ &self,
+ plan: &LogicalPlan,
+ props: &ExecutionProps,
+ ) -> Result<LogicalPlan> {
+ self.optimize_with_datetime(plan,
&props.query_execution_start_time.unwrap())
+ }
+
+ fn name(&self) -> &str {
+ "timestamp_evaluation"
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ use crate::logical_plan::LogicalPlanBuilder;
+ use crate::test::*;
+
+ fn get_optimized_plan_formatted(plan: &LogicalPlan) -> String {
+ let rule = TimestampEvaluation::new();
+ let execution_props = ExecutionProps {
+ query_execution_start_time: Some(chrono::Utc::now()),
+ };
+
+ let optimized_plan = rule
+ .optimize(plan, &execution_props)
+ .expect("failed to optimize plan");
+ return format!("{:?}", optimized_plan);
+ }
+
+ #[test]
+ fn single_now() {
+ let table_scan = test_table_scan().unwrap();
+ let proj = vec![Expr::ScalarFunction {
+ args: vec![],
+ fun: BuiltinScalarFunction::Now,
+ }];
+ let plan = LogicalPlanBuilder::from(&table_scan)
+ .project(proj)
+ .unwrap()
+ .build()
+ .unwrap();
+
+ let expected = "Projection: TimestampNanosecond(";
+ assert!(get_optimized_plan_formatted(&plan).starts_with(expected));
+ }
+
+ #[test]
+ fn double_now() {
+ let table_scan = test_table_scan().unwrap();
+ let proj = vec![
+ Expr::ScalarFunction {
+ args: vec![],
+ fun: BuiltinScalarFunction::Now,
+ },
+ Expr::Alias(
+ Box::new(Expr::ScalarFunction {
+ args: vec![],
+ fun: BuiltinScalarFunction::Now,
+ }),
+ "t2".to_string(),
+ ),
+ ];
+ let plan = LogicalPlanBuilder::from(&table_scan)
+ .project(proj)
+ .unwrap()
+ .build()
+ .unwrap();
+
+ let actual = get_optimized_plan_formatted(&plan);
+ println!("output is {}", &actual);
+ let expected_start = "Projection: TimestampNanosecond(";
+ assert!(actual.starts_with(expected_start));
+
+ let expected_end = ") AS t2\
+ \n TableScan: test projection=None";
+ assert!(actual.ends_with(expected_end));
Review comment:
It would probably be good here to ensure the same timestamp value was
produced in place `now()` was replaced.
Since you can specify what timestamp value goes in perhaps you could hard
code it in the test (so you could compare the plan with a known constant
string). Perhaps something like:
```
let start_time = Utc.ymd(2018, 7, 1).and_hms(6, 0, 0); //
2018-Jul-01 06:00
let execution_props = ExecutionProps {
query_execution_start_time: Some(start_time),
};
```
##########
File path: datafusion/src/physical_plan/functions.rs
##########
@@ -3611,17 +3607,19 @@ mod tests {
Ok(())
}
- #[test]
- fn test_concat_error() -> Result<()> {
Review comment:
I think it would be valuable to update the test case
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