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Spring Data Relational support

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/*
 * Copyright 2019-2023 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.data.relational.core.sql;

/**
 * Supertype of all Abstract Syntax Tree (AST) segments. Segments are typically immutable and mutator methods return new
 * instances instead of changing the called instance.
 *
 * @author Mark Paluch
 * @since 1.1
 */
public interface Segment extends Visitable {

	/**
	 * Check whether this {@link Segment} is equal to another {@link Segment}.
	 * 
	 * Equality is typically given if the {@link #toString()} representation matches.
	 * 
	 * 
	 * @param other the reference object with which to compare.
	 * @return {@literal true} if this object is the same as the {@code other} argument; {@literal false} otherwise.
	 */
	@Override
	boolean equals(Object other);

	/**
	 * Generate a hash code from this{@link Segment}.
	 * 
	 * Hashcode typically derives from the {@link #toString()} representation so two {@link Segment}s yield the same
	 * {@link #hashCode()} if their {@link #toString()} representation matches.
	 * 
	 * 
	 * @return a hash code value for this object.
	 */
	@Override
	int hashCode();

	/**
	 * Return a SQL string representation of this {@link Segment}.
	 * 
	 * The representation is intended for debugging purposes and an approximation to the generated SQL. While it might
	 * work in the context of a specific dialect, you should not assume that the {@link #toString()} representation works across
	 * multiple databases.
	 * 
	 * 
	 * @return a SQL string representation of this {@link Segment}.
	 */
	@Override
	String toString();
}