| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to you 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 org.apache.calcite.rel; |
| |
| import org.apache.calcite.sql.SqlExplainLevel; |
| import org.apache.calcite.util.Pair; |
| |
| import java.util.List; |
| |
| /** |
| * Callback for an expression to dump itself to. |
| * |
| * <p>It is used for generating EXPLAIN PLAN output, and also for serializing |
| * a tree of relational expressions to JSON.</p> |
| */ |
| public interface RelWriter { |
| /** |
| * Prints an explanation of a node, with a list of (term, value) pairs. |
| * |
| * <p>The term-value pairs are generally gathered by calling |
| * {@link org.apache.calcite.rel.RelNode#explain(RelWriter)}. |
| * Each sub-class of {@link org.apache.calcite.rel.RelNode} |
| * calls {@link #input(String, org.apache.calcite.rel.RelNode)} |
| * and {@link #item(String, Object)} to declare term-value pairs.</p> |
| * |
| * @param rel Relational expression |
| * @param valueList List of term-value pairs |
| */ |
| void explain(RelNode rel, List<Pair<String, Object>> valueList); |
| |
| /** |
| * @return detail level at which plan should be generated |
| */ |
| SqlExplainLevel getDetailLevel(); |
| |
| /** |
| * Adds an input to the explanation of the current node. |
| * |
| * @param term Term for input, e.g. "left" or "input #1". |
| * @param input Input relational expression |
| */ |
| default RelWriter input(String term, RelNode input) { |
| return item(term, input); |
| } |
| |
| /** |
| * Adds an attribute to the explanation of the current node. |
| * |
| * @param term Term for attribute, e.g. "joinType" |
| * @param value Attribute value |
| */ |
| RelWriter item(String term, Object value); |
| |
| /** |
| * Adds an input to the explanation of the current node, if a condition |
| * holds. |
| */ |
| default RelWriter itemIf(String term, Object value, boolean condition) { |
| return condition ? item(term, value) : this; |
| } |
| |
| /** |
| * Writes the completed explanation. |
| */ |
| RelWriter done(RelNode node); |
| |
| /** |
| * Returns whether the writer prefers nested values. Traditional explain |
| * writers prefer flattened values. |
| */ |
| default boolean nest() { |
| return false; |
| } |
| } |
| |
| // End RelWriter.java |