add plan optimizer for clp connector

Author: wraymo

presto-clp/src/main/java/com/facebook/presto/plugin/clp/ClpExpression.java

@@ -0,0 +1,70 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.facebook.presto.plugin.clp;
+
+import com.facebook.presto.spi.relation.RowExpression;
+
+import java.util.Optional;
+
+/**
+ * Represents the result of converting a Presto RowExpression into a CLP-compatible KQL query.
+ * There are three possible cases:
+ * 1. The entire RowExpression is convertible to KQL: `definition` is set, `remainingExpression` is empty.
+ * 2. Part of the RowExpression is convertible: the KQL part is stored in `definition`,
+ *    and the remaining untranslatable part is stored in `remainingExpression`.
+ * 3. None of the expression is convertible: the full RowExpression is stored in `remainingExpression`,
+ *    and `definition` is empty.
+ */
+public class ClpExpression
+{
+    // Optional KQL query string representing the fully or partially translatable part of the expression.
+    private final Optional<String> definition;
+
+    // The remaining (non-translatable) portion of the RowExpression, if any.
+    private final Optional<RowExpression> remainingExpression;
+
+    public ClpExpression(String definition, RowExpression remainingExpression)
+    {
+        this.definition = Optional.ofNullable(definition);
+        this.remainingExpression = Optional.ofNullable(remainingExpression);
+    }
+
+    // Creates an empty ClpExpression (no KQL definition, no remaining expression).
+    public ClpExpression()
+    {
+        this (null, null);
+    }
+
+    // Creates a ClpExpression from a fully translatable KQL string.
+    public ClpExpression(String definition)
+    {
+        this(definition, null);
+    }
+
+    // Creates a ClpExpression from a non-translatable RowExpression.
+    public ClpExpression(RowExpression remainingExpression)
+    {
+        this(null, remainingExpression);
+    }
+
+    public Optional<String> getDefinition()
+    {
+        return definition;
+    }
+
+    public Optional<RowExpression> getRemainingExpression()
+    {
+        return remainingExpression;
+    }
+}