ESQL: Rework building evaluators (#113979) (#114139)

This reworks `EvaluatorMapper` to use a named interface instead of a
`Function<Expression, EvalOperator.ExpressionEvaluator.Factory>`. It's
shorter to type and it allows us to add extra information to the
builder.

Author: nik9000

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

@@ -14,15 +14,17 @@
 import org.elasticsearch.xpack.esql.core.expression.Expression;
 import org.elasticsearch.xpack.esql.planner.Layout;
 
-import java.util.function.Function;
-
 import static org.elasticsearch.compute.data.BlockUtils.fromArrayRow;
 import static org.elasticsearch.compute.data.BlockUtils.toJavaObject;
 
 /**
  * Expressions that have a mapping to an {@link ExpressionEvaluator}.
  */
 public interface EvaluatorMapper {
+    interface ToEvaluator {
+        ExpressionEvaluator.Factory apply(Expression expression);
+    }
+
     /**
      * <p>
      * Note for implementors:
@@ -50,7 +52,7 @@ public interface EvaluatorMapper {
      * garbage. Or return an evaluator that throws when run.
      * </p>
      */
-    ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator);
+    ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator);
 
     /**
      * Fold using {@link #toEvaluator} so you don't need a "by hand"

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/grouping/Bucket.java

@@ -39,7 +39,6 @@
 import java.time.ZoneOffset;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.function.Function;
 
 import static org.elasticsearch.common.logging.LoggerMessageFormat.format;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.FIRST;
@@ -241,7 +240,7 @@ public boolean foldable() {
     }
 
     @Override
-    public ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
+    public ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         if (field.dataType() == DataType.DATETIME) {
             Rounding.Prepared preparedRounding;
             if (buckets.dataType().isWholeNumber()) {

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/grouping/Categorize.java

@@ -36,7 +36,6 @@
 
 import java.io.IOException;
 import java.util.List;
-import java.util.function.Function;
 
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.DEFAULT;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isString;
@@ -107,7 +106,7 @@ static int process(
     }
 
     @Override
-    public ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
+    public ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         return new CategorizeEvaluator.Factory(
             source(),
             toEvaluator.apply(field),

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/conditional/Case.java

@@ -50,7 +50,7 @@ public final class Case extends EsqlScalarFunction {
     public static final NamedWriteableRegistry.Entry ENTRY = new NamedWriteableRegistry.Entry(Expression.class, "Case", Case::new);
 
     record Condition(Expression condition, Expression value) {
-        ConditionEvaluatorSupplier toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
+        ConditionEvaluatorSupplier toEvaluator(ToEvaluator toEvaluator) {
             return new ConditionEvaluatorSupplier(condition.source(), toEvaluator.apply(condition), toEvaluator.apply(value));
         }
     }
@@ -311,7 +311,7 @@ private Expression finishPartialFold(List<Expression> newChildren) {
     }
 
     @Override
-    public ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
+    public ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         List<ConditionEvaluatorSupplier> conditionsFactories = conditions.stream().map(c -> c.toEvaluator(toEvaluator)).toList();
         ExpressionEvaluator.Factory elseValueFactory = toEvaluator.apply(elseValue);
         ElementType resultType = PlannerUtils.toElementType(dataType());

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/conditional/Greatest.java

@@ -30,7 +30,6 @@
 
 import java.io.IOException;
 import java.util.List;
-import java.util.function.Function;
 import java.util.stream.Stream;
 
 import static org.elasticsearch.xpack.esql.core.type.DataType.NULL;
@@ -138,7 +137,7 @@ public boolean foldable() {
     }
 
     @Override
-    public ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
+    public ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         // force datatype initialization
         var dataType = dataType();
         ExpressionEvaluator.Factory[] factories = children().stream()

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/conditional/Least.java

@@ -30,7 +30,6 @@
 
 import java.io.IOException;
 import java.util.List;
-import java.util.function.Function;
 import java.util.stream.Stream;
 
 import static org.elasticsearch.xpack.esql.core.type.DataType.NULL;
@@ -136,7 +135,7 @@ public boolean foldable() {
     }
 
     @Override
-    public ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
+    public ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         // force datatype initialization
         var dataType = dataType();
 

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/convert/AbstractConvertFunction.java

@@ -34,7 +34,6 @@
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
-import java.util.function.Function;
 
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isTypeOrUnionType;
 
@@ -124,7 +123,7 @@ interface BuildFactory {
     protected abstract Map<DataType, BuildFactory> factories();
 
     @Override
-    public ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
+    public ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         return evaluator(toEvaluator.apply(field()));
     }
 

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/convert/FromBase64.java

@@ -29,7 +29,6 @@
 import java.io.IOException;
 import java.util.Base64;
 import java.util.List;
-import java.util.function.Function;
 
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isString;
 import static org.elasticsearch.xpack.esql.core.type.DataType.KEYWORD;
@@ -96,9 +95,7 @@ static BytesRef process(BytesRef field, @Fixed(includeInToString = false, build
     }
 
     @Override
-    public EvalOperator.ExpressionEvaluator.Factory toEvaluator(
-        Function<Expression, EvalOperator.ExpressionEvaluator.Factory> toEvaluator
-    ) {
+    public EvalOperator.ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         return switch (PlannerUtils.toElementType(field.dataType())) {
             case BYTES_REF -> new FromBase64Evaluator.Factory(source(), toEvaluator.apply(field), context -> new BytesRefBuilder());
             case NULL -> EvalOperator.CONSTANT_NULL_FACTORY;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/convert/ToBase64.java

@@ -29,7 +29,6 @@
 import java.io.IOException;
 import java.util.Base64;
 import java.util.List;
-import java.util.function.Function;
 
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.isString;
 import static org.elasticsearch.xpack.esql.core.type.DataType.KEYWORD;
@@ -90,9 +89,7 @@ static BytesRef process(BytesRef field, @Fixed(includeInToString = false, build
     }
 
     @Override
-    public EvalOperator.ExpressionEvaluator.Factory toEvaluator(
-        Function<Expression, EvalOperator.ExpressionEvaluator.Factory> toEvaluator
-    ) {
+    public EvalOperator.ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         return switch (PlannerUtils.toElementType(field.dataType())) {
             case BYTES_REF -> new ToBase64Evaluator.Factory(source(), toEvaluator.apply(field), context -> new BytesRefBuilder());
             case NULL -> EvalOperator.CONSTANT_NULL_FACTORY;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/date/DateDiff.java

@@ -37,7 +37,6 @@
 import java.util.Map;
 import java.util.Set;
 import java.util.function.BiFunction;
-import java.util.function.Function;
 
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.FIRST;
 import static org.elasticsearch.xpack.esql.core.expression.TypeResolutions.ParamOrdinal.SECOND;
@@ -227,7 +226,7 @@ static int process(BytesRef unit, long startTimestamp, long endTimestamp) throws
     }
 
     @Override
-    public ExpressionEvaluator.Factory toEvaluator(Function<Expression, ExpressionEvaluator.Factory> toEvaluator) {
+    public ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvaluator) {
         ExpressionEvaluator.Factory startTimestampEvaluator = toEvaluator.apply(startTimestamp);
         ExpressionEvaluator.Factory endTimestampEvaluator = toEvaluator.apply(endTimestamp);