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/*
 * 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,
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package com.hazelcast.org.apache.calcite.rel.hint;

import com.hazelcast.org.apache.calcite.rel.RelNode;

/**
 * A {@code HintPredicate} indicates whether a {@link com.hazelcast.org.apache.calcite.rel.RelNode}
 * can apply the specified hint.
 *
 * 

Every supported hint should register a {@code HintPredicate} * into the {@link HintStrategyTable}. For example, {@link HintPredicates#JOIN} implies * that this hint would be propagated and applied to the {@link com.hazelcast.org.apache.calcite.rel.core.Join} * relational expressions. * *

Usually use {@link NodeTypeHintPredicate} is enough for most of the {@link RelHint}s. * Some of the hints can only be matched to the relational expression with special * match conditions(not only the relational expression type). * i.e. "hash_join(r, st)", this hint can only be applied to JOIN expression that * has "r" and "st" as the input table names. To implement this, you can make a custom * {@code HintPredicate} instance. * *

A {@code HintPredicate} can be used independently or cascaded with other strategies * with method {@link HintPredicates#and}. * *

In {@link HintStrategyTable} the predicate is used for * hints registration. * * @see HintStrategyTable */ public interface HintPredicate { /** * Decides if the given {@code hint} can be applied to * the relational expression {@code rel}. * * @param hint The hint * @param rel The relational expression * @return True if the {@code hint} can be applied to the {@code rel} */ boolean apply(RelHint hint, RelNode rel); }





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