ESQL: Fix DEBUG log of filter (#116086) (#116100)

This fixes thet  `DEBUG` level logging of `WHERE`. Previously it was using
a `ThrowingDriverContext` to render the description - but this throwing
context will, well, throw if you touch it. This removes the
`ThrowingDriverContext` entirely because it's never the right thing to
use - instead we just use the `toString` of the factories. That works
fine because we made sure that the factories had a nice `toString`.

Closes #116055

Author: nik9000

docs/changelog/116086.yaml

@@ -0,0 +1,6 @@
+pr: 116086
+summary: "ESQL: Fix DEBUG log of filter"
+area: ES|QL
+type: bug
+issues:
+ - 116055

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/FilterOperator.java

@@ -28,7 +28,7 @@ public Operator get(DriverContext driverContext) {
 
         @Override
         public String describe() {
-            return "FilterOperator[evaluator=" + evaluatorSupplier.get(new ThrowingDriverContext()) + "]";
+            return "FilterOperator[evaluator=" + evaluatorSupplier + "]";
         }
     }
 

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/ThrowingDriverContext.java

@@ -53,7 +53,18 @@ public void close() {}
 
     @Override
     protected Operator.OperatorFactory simple() {
-        return new FilterOperator.FilterOperatorFactory(dvrCtx -> new SameLastDigit(dvrCtx, 0, 1));
+        return new FilterOperator.FilterOperatorFactory(new EvalOperator.ExpressionEvaluator.Factory() {
+
+            @Override
+            public EvalOperator.ExpressionEvaluator get(DriverContext context) {
+                return new SameLastDigit(context, 0, 1);
+            }
+
+            @Override
+            public String toString() {
+                return "SameLastDigit[lhs=0, rhs=1]";
+            }
+        });
     }
 
     @Override