remove ComparisonMapper (elastic#107896)

More follow-up work from elastic#105217. Since the binary comparison operators now implement EvaluatorMapper, there is no need for ComparisonMapper going forward.

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/evaluator/EvalMapper.java

@@ -22,7 +22,6 @@
 import org.elasticsearch.core.Releasables;
 import org.elasticsearch.xpack.esql.evaluator.mapper.EvaluatorMapper;
 import org.elasticsearch.xpack.esql.evaluator.mapper.ExpressionMapper;
-import org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.ComparisonMapper;
 import org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.InMapper;
 import org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.InsensitiveEqualsMapper;
 import org.elasticsearch.xpack.esql.planner.Layout;
@@ -40,12 +39,6 @@
 public final class EvalMapper {
 
     private static final List<ExpressionMapper<?>> MAPPERS = List.of(
-        ComparisonMapper.EQUALS,
-        ComparisonMapper.NOT_EQUALS,
-        ComparisonMapper.GREATER_THAN,
-        ComparisonMapper.GREATER_THAN_OR_EQUAL,
-        ComparisonMapper.LESS_THAN,
-        ComparisonMapper.LESS_THAN_OR_EQUAL,
         InMapper.IN_MAPPER,
         new InsensitiveEqualsMapper(),
         new BooleanLogic(),

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/evaluator/mapper/EvaluatorMapper.java

@@ -15,6 +15,7 @@
 import org.elasticsearch.compute.data.Page;
 import org.elasticsearch.compute.operator.DriverContext;
 import org.elasticsearch.compute.operator.EvalOperator.ExpressionEvaluator;
+import org.elasticsearch.xpack.esql.planner.Layout;
 import org.elasticsearch.xpack.ql.expression.Expression;
 
 import java.util.function.Function;
@@ -27,6 +28,22 @@
  */
 public interface EvaluatorMapper {
     /**
+     * <p>
+     * Note for implementors:
+     * If you are implementing this function, you should call the passed-in
+     * lambda on your children, after doing any other manipulation (casting,
+     * etc.) necessary.
+     * </p>
+     * <p>
+     * Note for Callers:
+     * If you are attempting to call this method, and you have an
+     * {@link Expression} and a {@link org.elasticsearch.xpack.esql.planner.Layout},
+     * you likely want to call {@link org.elasticsearch.xpack.esql.evaluator.EvalMapper#toEvaluator(Expression, Layout)}
+     * instead.  On the other hand, if you already have something that
+     * looks like the parameter for this method, you should call this method
+     * with that function.
+     * </p>
+     * <p>
      * Build an {@link ExpressionEvaluator.Factory} for the tree of
      * expressions rooted at this node. This is only guaranteed to return
      * a sensible evaluator if this node has a valid type. If this node
@@ -35,6 +52,7 @@ public interface EvaluatorMapper {
      * If {@linkplain Expression#typeResolved} returns an error then
      * this method may throw. Or return an evaluator that produces
      * garbage. Or return an evaluator that throws when run.
+     * </p>
      */
     ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator);
 

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/evaluator/predicate/operator/comparison/InMapper.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.compute.operator.EvalOperator;
 import org.elasticsearch.compute.operator.EvalOperator.ExpressionEvaluator;
 import org.elasticsearch.core.Releasables;
+import org.elasticsearch.xpack.esql.evaluator.EvalMapper;
 import org.elasticsearch.xpack.esql.evaluator.mapper.ExpressionMapper;
 import org.elasticsearch.xpack.esql.expression.predicate.operator.comparison.In;
 import org.elasticsearch.xpack.esql.planner.Layout;
@@ -24,8 +25,6 @@
 import java.util.BitSet;
 import java.util.List;
 
-import static org.elasticsearch.xpack.esql.evaluator.predicate.operator.comparison.ComparisonMapper.EQUALS;
-
 public class InMapper extends ExpressionMapper<In> {
 
     public static final InMapper IN_MAPPER = new InMapper();
@@ -38,7 +37,7 @@ public ExpressionEvaluator.Factory map(In in, Layout layout) {
         List<ExpressionEvaluator.Factory> listEvaluators = new ArrayList<>(in.list().size());
         in.list().forEach(e -> {
             Equals eq = new Equals(in.source(), in.value(), e);
-            ExpressionEvaluator.Factory eqEvaluator = ((ExpressionMapper) EQUALS).map(eq, layout);
+            ExpressionEvaluator.Factory eqEvaluator = EvalMapper.toEvaluator(eq, layout);
             listEvaluators.add(eqEvaluator);
         });
         return dvrCtx -> new InExpressionEvaluator(dvrCtx, listEvaluators.stream().map(fac -> fac.get(dvrCtx)).toList());