org.apache.jackrabbit.oak.spi.query.Cursor Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* 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
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* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.jackrabbit.oak.spi.query;
import java.util.Iterator;
import org.apache.jackrabbit.oak.api.Result.SizePrecision;
/**
* A cursor to read a number of nodes sequentially.
*/
public interface Cursor extends Iterator {
/**
* The next row within this index.
*
* The row may only contains the path, if a path is available. It may also
* (or just) contain so-called "pseudo-properties" such as "jcr:score" and
* "rep:excerpt", in case the index supports those properties and if the
* properties were requested when running the query. The query engine will
* indicate that those pseudo properties were requested by setting an
* appropriate (possibly unrestricted) filter condition.
*
* The index should return a row with those properties that are stored in
* the index itself, so that the query engine doesn't have to load the whole
* row / node unnecessarily (avoiding to load the whole row is sometimes
* called "index only scan"), specially for rows that are anyway skipped. If
* the index does not have an (efficient) way to return some (or any) of the
* properties, it doesn't have to provide those values. In this case, the
* query engine will load the node itself if required. If all conditions
* match, the query engine will sometimes load the node to do access checks,
* but this is not always the case, and it is not the case if any of the
* (join) conditions do not match.
*
* @return the row
*/
@Override
IndexRow next();
/**
* Get the size if known.
*
* @param precision the required precision
* @param max the maximum nodes read (for an exact size)
* @return the size, or -1 if unknown
*/
long getSize(SizePrecision precision, long max);
}