ozankabak commented on code in PR #14279:
URL: https://github.com/apache/datafusion/pull/14279#discussion_r1929486166


##########
datafusion/physical-expr/src/analysis.rs:
##########
@@ -191,7 +201,18 @@ pub fn analyze(
             shrink_boundaries(graph, target_boundaries, 
target_expr_and_indices)
         }
         PropagationResult::Infeasible => {
-            Ok(AnalysisContext::new(target_boundaries).with_selectivity(0.0))
+            // If the propagation result is infeasible, map target boundary 
intervals to None
+            Ok(AnalysisContext::new(

Review Comment:
   You seem to already own `target_boundaries`, no need to create a new 
`ExprBoundaries` object. Just iterate over `target_boundaries` mutably and 
assign `None` to the `interval` attribute.



##########
datafusion/physical-expr/src/analysis.rs:
##########
@@ -179,7 +179,17 @@ pub fn analyze(
                 expr.as_any()
                     .downcast_ref::<Column>()
                     .filter(|expr_column| bound.column.eq(*expr_column))
-                    .map(|_| (*i, bound.interval.clone()))
+                    .map(|_| {
+                        (
+                            *i,
+                            match bound.interval.clone() {

Review Comment:
   This function already returns a `Result`. You should return an error here 
and not panic with `unreachable!`. Also doing the cloning *after* checking for 
`None` is a slightly better style.



##########
datafusion/physical-expr/src/analysis.rs:
##########
@@ -335,7 +355,9 @@ mod tests {
                 df_schema.as_ref(),
             )
             .unwrap();
-            let actual = &analysis_result.boundaries[0].interval;
+            let Some(actual) = &analysis_result.boundaries[0].interval else {
+                panic!("Interval should be initialized for all columns");

Review Comment:
   ```suggestion
                   panic!("The analysis result should contain non-empty 
intervals for all columns");
   ```
   AFAICT this is not about initialization, you expect non-empty results.



##########
datafusion/physical-expr/src/analysis.rs:
##########
@@ -82,7 +82,7 @@ impl AnalysisContext {
 pub struct ExprBoundaries {
     pub column: Column,
     /// Minimum and maximum values this expression can have.

Review Comment:
   ```suggestion
       /// Minimum and maximum values this expression can have. A `None` value
       /// represents an infeasible expression.
   ```



##########
datafusion/physical-plan/src/filter.rs:
##########
@@ -421,7 +421,18 @@ fn collect_new_statistics(
                     ..
                 },
             )| {
-                let (lower, upper) = interval.into_bounds();
+                let (lower, upper) = match interval {
+                    Some(interval) => interval.into_bounds(),
+                    // If the interval is None, we can say that there are no 
rows
+                    None => {
+                        return ColumnStatistics {
+                            null_count: Precision::Exact(0),
+                            max_value: 
Precision::Exact(ScalarValue::Int32(Some(0))),
+                            min_value: 
Precision::Exact(ScalarValue::Int32(Some(0))),
+                            distinct_count: Precision::Exact(0),
+                        }
+                    }
+                };

Review Comment:
   ```suggestion
                   let Some(interval) = interval else {
                       // If the interval is `None`, we can say that there are 
no rows:
                       return ColumnStatistics {
                           null_count: Precision::Exact(0),
                           max_value: 
Precision::Exact(ScalarValue::Int32(Some(0))),
                           min_value: 
Precision::Exact(ScalarValue::Int32(Some(0))),
                           distinct_count: Precision::Exact(0),
                       };
                   };
                   let (lower, upper) = interval.into_bounds();
   ```



##########
datafusion/physical-expr/src/analysis.rs:
##########
@@ -235,16 +256,25 @@ fn shrink_boundaries(
 fn calculate_selectivity(
     target_boundaries: &[ExprBoundaries],
     initial_boundaries: &[ExprBoundaries],
-) -> f64 {
+) -> Result<f64> {
     // Since the intervals are assumed uniform and the values
     // are not correlated, we need to multiply the selectivities
     // of multiple columns to get the overall selectivity.
+    let mut acc: f64 = 1.0;
     initial_boundaries
         .iter()
         .zip(target_boundaries.iter())
-        .fold(1.0, |acc, (initial, target)| {
-            acc * cardinality_ratio(&initial.interval, &target.interval)
-        })
+        .for_each(|(initial, target)| {

Review Comment:
   Similar to above -- let's return a `Result` instead of panicking and do any 
checks before clones. Also, given that this is a good old for loop now, it will 
increase readability to switch to a simple `for` statement instead of using a 
closure within the `for_each` method.



##########
datafusion/physical-expr/src/analysis.rs:
##########
@@ -344,6 +366,41 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_analyze_empty_set_boundary_exprs() {
+        let schema = Arc::new(Schema::new(vec![make_field("a", 
DataType::Int32)]));
+
+        let test_cases: Vec<Expr> = vec![
+            // a > 10 AND a < 10
+            col("a").gt(lit(10)).and(col("a").lt(lit(10))),
+            // a > 5 AND (a < 20 OR a > 20)
+            // a > 10 AND a < 20
+            // (a > 10 AND a < 20) AND (a > 20 AND a < 30)
+            col("a")
+                .gt(lit(10))
+                .and(col("a").lt(lit(20)))
+                .and(col("a").gt(lit(20)))
+                .and(col("a").lt(lit(30))),
+        ];
+
+        for expr in test_cases {
+            let boundaries = 
ExprBoundaries::try_new_unbounded(&schema).unwrap();
+            let df_schema = DFSchema::try_from(Arc::clone(&schema)).unwrap();
+            let physical_expr =
+                create_physical_expr(&expr, &df_schema, 
&ExecutionProps::new()).unwrap();
+            let analysis_result = analyze(
+                &physical_expr,
+                AnalysisContext::new(boundaries),
+                df_schema.as_ref(),
+            )
+            .unwrap();
+
+            analysis_result.boundaries.iter().for_each(|bound| {

Review Comment:
   Good old for loop is preferable in cases like this



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