Minor: avoid a clone in type coercion (#11530)

* Minor: avoid a clone in type coercion

* Fix test

Author: alamb

datafusion/optimizer/src/analyzer/type_coercion.rs

@@ -84,7 +84,7 @@ impl AnalyzerRule for TypeCoercion {
 /// Assumes that children have already been optimized
 fn analyze_internal(
     external_schema: &DFSchema,
-    mut plan: LogicalPlan,
+    plan: LogicalPlan,
 ) -> Result<Transformed<LogicalPlan>> {
     // get schema representing all available input fields. This is used for data type
     // resolution only, so order does not matter here
@@ -103,15 +103,13 @@ fn analyze_internal(
     // select t2.c2 from t1 where t1.c1 in (select t2.c1 from t2 where t2.c2=t1.c3)
     schema.merge(external_schema);
 
-    if let LogicalPlan::Filter(filter) = &mut plan {
-        if let Ok(new_predicate) = filter
-            .predicate
-            .clone()
-            .cast_to(&DataType::Boolean, filter.input.schema())
-        {
-            filter.predicate = new_predicate;
-        }
-    }
+    // Coerce filter predicates to boolean (handles `WHERE NULL`)
+    let plan = if let LogicalPlan::Filter(mut filter) = plan {
+        filter.predicate = filter.predicate.cast_to(&DataType::Boolean, &schema)?;
+        LogicalPlan::Filter(filter)
+    } else {
+        plan
+    };
 
     let mut expr_rewrite = TypeCoercionRewriter::new(&schema);
 

datafusion/sqllogictest/test_files/misc.slt

@@ -30,6 +30,10 @@ query I
 select 1 where NULL
 ----
 
+# Where clause does not accept non boolean and has nice error message
+query error Cannot create filter with non\-boolean predicate 'Utf8\("foo"\)' returning Utf8
+select 1 where 'foo'
+
 query I
 select 1 where NULL and 1 = 1
 ----