Fix some attr.name() usages that meant field names

Author: alex-spies

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/FieldAttribute.java

@@ -175,7 +175,7 @@ public FieldAttribute exactAttribute() {
     }
 
     private FieldAttribute innerField(EsField type) {
-        return new FieldAttribute(source(), name(), name() + "." + type.getName(), type, nullable(), id(), synthetic());
+        return new FieldAttribute(source(), fieldName().string, name() + "." + type.getName(), type, nullable(), id(), synthetic());
     }
 
     @Override

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/enrich/AbstractLookupService.java

@@ -71,6 +71,7 @@
 import org.elasticsearch.transport.TransportService;
 import org.elasticsearch.xpack.esql.EsqlIllegalArgumentException;
 import org.elasticsearch.xpack.esql.core.expression.Alias;
+import org.elasticsearch.xpack.esql.core.expression.FieldAttribute;
 import org.elasticsearch.xpack.esql.core.expression.NamedExpression;
 import org.elasticsearch.xpack.esql.core.tree.Source;
 import org.elasticsearch.xpack.esql.core.type.DataType;
@@ -415,8 +416,12 @@ private static Operator extractFieldsOperator(
     ) {
         List<ValuesSourceReaderOperator.FieldInfo> fields = new ArrayList<>(extractFields.size());
         for (NamedExpression extractField : extractFields) {
-            BlockLoader loader = shardContext.blockLoader(
-                extractField instanceof Alias a ? ((NamedExpression) a.child()).name() : extractField.name(),
+            String fieldName = extractField instanceof FieldAttribute fa ? fa.fieldName().string()
+                // Cases for Alias and ReferenceAttribute: only required for ENRICH (Alias in case of ENRICH ... WITH x = field)
+                // (LOOKUP JOIN uses FieldAttributes)
+                : extractField instanceof Alias a ? ((NamedExpression) a.child()).name()
+                : extractField.name();
+            BlockLoader loader = shardContext.blockLoader(fieldName,
                 extractField.dataType() == DataType.UNSUPPORTED,
                 MappedFieldType.FieldExtractPreference.NONE
             );

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plan/logical/join/Join.java

@@ -158,6 +158,9 @@ public AttributeSet rightReferences() {
         return Expressions.references(config().rightFields());
     }
 
+    /**
+     * The output fields obtained from the right child.
+     */
     public List<Attribute> rightOutputFields() {
         AttributeSet leftInputs = left().outputSet();