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[refactor] Add a Materializable interface to explicitly mark which ex…
…pressions use the Materialization query execution model
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exist-core/src/main/java/org/exist/xquery/Materializable.java
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| /* | ||
| * Copyright (C) 2014, Evolved Binary Ltd | ||
| * | ||
| * This file was originally ported from FusionDB to eXist-db by | ||
| * Evolved Binary, for the benefit of the eXist-db Open Source community. | ||
| * Only the ported code as it appears in this file, at the time that | ||
| * it was contributed to eXist-db, was re-licensed under The GNU | ||
| * Lesser General Public License v2.1 only for use in eXist-db. | ||
| * | ||
| * This license grant applies only to a snapshot of the code as it | ||
| * appeared when ported, it does not offer or infer any rights to either | ||
| * updates of this source code or access to the original source code. | ||
| * | ||
| * The GNU Lesser General Public License v2.1 only license follows. | ||
| * | ||
| * --------------------------------------------------------------------- | ||
| * | ||
| * Copyright (C) 2014, Evolved Binary Ltd | ||
| * | ||
| * This library is free software; you can redistribute it and/or | ||
| * modify it under the terms of the GNU Lesser General Public | ||
| * License as published by the Free Software Foundation; version 2.1. | ||
| * | ||
| * This library is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
| * Lesser General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU Lesser General Public | ||
| * License along with this library; if not, write to the Free Software | ||
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | ||
| */ | ||
| package org.exist.xquery; | ||
|
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| import org.exist.xquery.value.Item; | ||
| import org.exist.xquery.value.Sequence; | ||
|
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| import javax.annotation.Nullable; | ||
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| /** | ||
| * Marks an expression as being Materializable as per the | ||
| * Materialization query execution model. | ||
| * | ||
| * @author <a href="mailto:[email protected]">Adam Retter</a> | ||
| */ | ||
| public interface Materializable { | ||
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|
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| /** | ||
| * Materialize the result. | ||
| * | ||
| * Depending on the context in which this expression is executed, | ||
| * either the context sequence, the context item or both of them may | ||
| * be set. An implementing class should know how to handle this. | ||
| * | ||
| * The general contract is as follows: if the {@link Dependency#CONTEXT_ITEM} | ||
| * bit is set in the bit field returned by {@link Expression#getDependencies()}, the eval method will | ||
| * be called once for every item in the context sequence. The <b>contextItem</b> | ||
| * parameter will be set to the current item. Otherwise, the eval method will only be called | ||
| * once for the whole context sequence and <b>contextItem</b> will be null. | ||
| * | ||
| * eXist-db tries to process the entire context set in one, single step whenever | ||
| * possible. Thus, most classes only expect context to contain a list of | ||
| * nodes which represents the current context of the expression. | ||
| * | ||
| * The position() function in XPath is an example for an expression, | ||
| * which requires both, context sequence and context item to be set. | ||
| * | ||
| * The context sequence might be a node set, a sequence of atomic values or a single | ||
| * node or atomic value. | ||
| * | ||
| * @param contextSequence the current context sequence, or null if there is no context sequence. | ||
| * @param contextItem a single item, taken from context, or null if there is no context item. | ||
| * This defines the item, the expression should work on. | ||
| * | ||
| * @return the result sequence. | ||
| * | ||
| * @throws XPathException if an error occurs during evaluation. | ||
| */ | ||
| Sequence eval(@Nullable Sequence contextSequence, @Nullable Item contextItem) throws XPathException; | ||
| } |