Break QueryTranslator into QL and SQL (#52397)

Refactor the code to allow contextual parameterization of dateFormat and
name.
Separate aggs/query implementation though there's room for improvement in the future

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/planner/ExpressionTranslator.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.ql.planner;
+
+import org.elasticsearch.xpack.ql.expression.Expression;
+import org.elasticsearch.xpack.ql.expression.FieldAttribute;
+import org.elasticsearch.xpack.ql.querydsl.query.NestedQuery;
+import org.elasticsearch.xpack.ql.querydsl.query.Query;
+import org.elasticsearch.xpack.ql.util.ReflectionUtils;
+
+public abstract class ExpressionTranslator<E extends Expression> {
+
+    private final Class<E> typeToken = ReflectionUtils.detectSuperTypeForRuleLike(getClass());
+
+    @SuppressWarnings("unchecked")
+    public Query translate(Expression exp, TranslatorHandler handler) {
+        return (typeToken.isInstance(exp) ? asQuery((E) exp, handler) : null);
+    }
+
+    protected abstract Query asQuery(E e, TranslatorHandler handler);
+
+    public static Query wrapIfNested(Query query, Expression exp) {
+        if (query != null && exp instanceof FieldAttribute) {
+            FieldAttribute fa = (FieldAttribute) exp;
+            if (fa.isNested()) {
+                return new NestedQuery(fa.source(), fa.nestedParent().name(), query);
+            }
+        }
+        return query;
+    }
+}

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/planner/QlTranslatorHandler.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.ql.planner;
+
+import org.elasticsearch.xpack.ql.expression.Expression;
+import org.elasticsearch.xpack.ql.expression.FieldAttribute;
+import org.elasticsearch.xpack.ql.expression.NamedExpression;
+import org.elasticsearch.xpack.ql.expression.function.scalar.ScalarFunction;
+import org.elasticsearch.xpack.ql.querydsl.query.Query;
+import org.elasticsearch.xpack.ql.querydsl.query.ScriptQuery;
+
+public class QlTranslatorHandler implements TranslatorHandler {
+
+    @Override
+    public Query asQuery(Expression e) {
+        return ExpressionTranslators.toQuery(e, this);
+    }
+
+    @Override
+    public Query wrapFunctionQuery(ScalarFunction sf, Expression field, Query q) {
+        if (field instanceof FieldAttribute) {
+            return ExpressionTranslator.wrapIfNested(q, field);
+        }
+        return new ScriptQuery(sf.source(), sf.asScript());
+    }
+
+    @Override
+    public String nameOf(Expression e) {
+        if (e instanceof NamedExpression) {
+            return ((NamedExpression) e).name();
+        } else {
+            return e.sourceText();
+        }
+    }
+
+    @Override
+    public String dateFormat(Expression e) {
+        return null;
+    }
+}

x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/planner/TranslatorHandler.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+package org.elasticsearch.xpack.ql.planner;
+
+import org.elasticsearch.xpack.ql.expression.Expression;
+import org.elasticsearch.xpack.ql.expression.function.scalar.ScalarFunction;
+import org.elasticsearch.xpack.ql.querydsl.query.Query;
+
+/**
+ * Parameterized handler used during query translation.
+ * 
+ * Provides contextual utilities for an individual query to be performed.
+ */
+public interface TranslatorHandler {
+
+    Query asQuery(Expression e);
+
+    Query wrapFunctionQuery(ScalarFunction sf, Expression field, Query q);
+
+    String nameOf(Expression e);
+
+    String dateFormat(Expression e);
+}

x-pack/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/planner/QueryFolder.java

@@ -30,6 +30,7 @@
 import org.elasticsearch.xpack.ql.expression.gen.pipeline.UnaryPipe;
 import org.elasticsearch.xpack.ql.expression.gen.processor.Processor;
 import org.elasticsearch.xpack.ql.expression.gen.script.ScriptTemplate;
+import org.elasticsearch.xpack.ql.planner.ExpressionTranslators;
 import org.elasticsearch.xpack.ql.querydsl.query.Query;
 import org.elasticsearch.xpack.ql.rule.Rule;
 import org.elasticsearch.xpack.ql.rule.RuleExecutor;
@@ -90,7 +91,6 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 import static org.elasticsearch.xpack.ql.util.CollectionUtils.combine;
-import static org.elasticsearch.xpack.sql.planner.QueryTranslator.and;
 import static org.elasticsearch.xpack.sql.planner.QueryTranslator.toAgg;
 import static org.elasticsearch.xpack.sql.planner.QueryTranslator.toQuery;
 import static org.elasticsearch.xpack.sql.type.SqlDataTypes.DATE;
@@ -181,7 +181,7 @@ protected PhysicalPlan rule(FilterExec plan) {
 
                 Query query = null;
                 if (qContainer.query() != null || qt.query != null) {
-                    query = and(plan.source(), qContainer.query(), qt.query);
+                    query = ExpressionTranslators.and(plan.source(), qContainer.query(), qt.query);
                 }
                 Aggs aggs = addPipelineAggs(qContainer, qt, plan);