org.apache.jackrabbit.oak.api.Result Maven / Gradle / Ivy
/*
* 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.jackrabbit.oak.api;
/**
* A result from executing a query.
*/
public interface Result {
/**
* Get the list of column names.
*
* @return the column names
*/
String[] getColumnNames();
/**
* Get the distinct selector names of all columns. The list is ordered as
* selectors appear in the result. For columns without selector, an empty
* entry (null) is used.
*
* @return the distinct selector names
*/
String[] getColumnSelectorNames();
/**
* Get the list of selector names.
*
* @return the selector names
*/
String[] getSelectorNames();
/**
* Get the rows.
*
* @return the rows
*/
Iterable getRows();
/**
* Get the number of rows, if known. If the size is not known, -1 is
* returned.
*
* @return the size or -1 if unknown
*/
long getSize();
/**
* Get the number of rows, if known. If the size is not known, -1 is
* returned.
*
* @param precision the required precision
* @param max the maximum number that should be returned (Long.MAX_VALUE for
* unlimited). For EXACT, the cost of the operation is at most
* O(max). For approximations, the cost of the operation should
* be at most O(log max).
* @return the (approximate) size. If an implementation does know the exact
* value, it returns it (even if the value is higher than max). If
* the implementation does not know the value, and the child node
* count is higher than max, it returns Long.MAX_VALUE.
*/
long getSize(SizePrecision precision, long max);
enum SizePrecision {
/**
* If the exact number is needed.
*/
EXACT,
/**
* If a good, and secure estimate is needed (the actual number can be
* lower or higher). This is supposed to be faster than exact count, but
* slower than a fast approximation.
*/
APPROXIMATION,
/**
* If a rough estimate is needed (the actual number can be lower or
* higher). This is supposed to be faster than a good approximation. It
* could be (for example) the expected cost of the query.
*/
FAST_APPROXIMATION,
}
}